INTRODUCTION
The numbers and types of bacteria which enter the host via the oral cavity is greater than that which enters through all the other body orifices combined. While most of these organisms cannot survive on the mucous membranes, some not only could survive, but could cause infections. The host responds to these exogenous organisms with several antibacterial proteins which are always present in the saliva and which react without an obvious specificity against a heterogeneous array of bacterial types. At another level the host mounts a specific antibody response to various bacterial types which is mediated by not only the classic serum immunoglobulins but by a unique class of immunoglobulins known as secretory IgA. Collectively these defense mechanisms account for the virtual absence of serious bacterial infections emanating from the oral cavity.
The nonspecific mechanisms are for the most part poorly understood, but in recent years under the impetus created by the desirability of an anticaries vaccine, much has been learned concerning the role of specific antibodies in the regulation of S. mutans infections. Often the specific and the nonspecific mechanisms have a common final step, namely the clumping of bacteria so that they are cleared from the oral cavity. While bactericidal mechanisms occur, they do not seem to have the same importance as the clearance mechanisms. This will become apparent from the studies to be described in this chapter.
前言
從口腔進入宿主的細菌種類和數量遠遠大於從其他身體開口進入細菌的總和。所幸除了少數一些特定的菌種外，大部份的細菌並沒有辦法存活於人體黏膜上。然而這些少數的菌種不但得以存活還會造成感染。一般宿主的抗菌機制是啟動唾液裡的非特異性的抗菌蛋白對抗這些外來菌，而這樣的機制並沒有菌種特定性。另外宿主也有對抗特定細菌的抗體反應，是由典型的血漿球蛋白或是特定的免疫球蛋白(例如secretory IgA)啟動。這兩種抗菌機制相輔相成使得宿主免於產生嚴重的細菌感染。
NON-IMMUNE ANTIBACTERIAL MECHANISMS
There are several salivary proteins or glycoproteins, such as lysozyme, lactoperoxidase, lactoferrin and high molecular weight agglutinins (Table 20-1), which possess antibacterial activities. These proteins are chemically distinct from immunoglobulins, are present at relatively constant levels, exhibit broad spectrum activity and lack any aspects of immunological memory. Those organisms which colonize the oral surfaces seem to be resistant to these proteins, and this characteristic could have contributed to their selection as members of the indigenous oral flora. These proteins do not appear to be of importance in caries protection, as their levels are similar in caries-free and caries-susceptible individuals. However, in vitro, these proteins can inhibit or aggregate S. mutans to varying degrees, and accordingly they might play some role in vivo in regard to S. mutans colonization.
非免疫性抗菌機制 (NON-IMMUNE ANTIBACTERIAL MECHANISMS)
有許多唾液蛋白或球蛋白(例如: lysozyme, lactoperoxidase, lactoferrin以及高分子量的agglutinins)都有抗菌的能力(見表20-1)。這些蛋白在化學結構上和免疫球蛋不同，在人體裡常態性的保持一定濃度，可以對抗細菌的範圍很廣並且沒有免疫記憶專一性。能夠在口腔黏膜中存活的外來菌種多對這些蛋白有抵抗力，只有這樣的菌種能夠在口腔環境中被選擇留下來而自成菌落。這些非特異性蛋白對於防止蛀牙似乎沒有太大影響，因為在無蛀牙和容易蛀牙的個體裡，這些蛋白的濃度並沒有差異。然而，在實驗室裡，這些蛋白可以在某些程度上抑制或是聚集S. mutans，所以在人體裡的S. mutans聚集菌落，這些蛋白可能仍扮演某種重要的角色。
Lysozyme
Lysozyme is a low molecular weight basic protein that is present in high concentrations in the saliva. The actual concentrations vary inversely with the salivary flow rate and range from four to six mg/l00 ml. At high flow rates there will be about 20 micro-grams of lysozyme secreted per minute, whereas about nine micro-grams per minute is secreted at low flow rates.
The highly cationic nature of lysozyme suggests that it will act as an adhesive molecule for the bacterial surfaces. Purified lysozyme has six active sites which bind to carbohydrate receptors on the cell surface in a lectin-like manner (carbohydrate-protein interaction). If the bound lysozyme gains access to the cell wall peptidoglycan, the lysozyme acts as a muramidase, causing cell lysis. Most oral species are resistant to this lysis, and it is doubtful whether such lysis occurs in vivo in the oral cavity. Lysozyme can kill bacteria by inhibiting the respiratory system located in the cell membrane or by activating an endogenous autolytic enzyme system. However, the most likely antibacterial role of lysozyme in the saliva may be the aggregation of bacteria so that they can no longer attach to oral surfaces.
Studies by Pollack and his colleagues indicate that lysozyme binds to the various S. mutans serotypes, but at significantly different rates (Table 20-2). Serotypes a and b strains become saturated with lysozyme within 12 to 15 minutes, whereas three hours are required for the other serotypes to become saturated. The growth of serotype a and b strains in vitro was inhibited by 50 mg of lysozyme, whereas 20 to 100 fold higher levels were necessary to inhibit the other serotypes (Table 20-2). These findings predict that serotype a and b strains could be influenced in vivo by lysozyme, a fact which could account for the low frequency with which these serotypes are encountered in human plaque samples.
Lysozyme
Lysozyme是種在唾液裡濃度很高的低分子量基本蛋白。他的實際濃度與唾液流量正好成反比，大約4~6 mg/100 ml。在高流量時一分鐘約有20 微克的lysozyme被分泌而低流量時一分鐘約有9微克。 (?這裡我不懂為何成反比 vary inversely 但後來的例子卻是成正比!!??)
Lysozyme分子表面帶高正電陽離子，使得它很容易和細菌表面黏附。純化的lysozyme表面有6個活潑的位子可以和細胞表面的碳水化合物接受器產生lectin-like方式結合 (carbohydrate-protein interaction)。理論上lysozyme黏上細菌的會形成細胞壁上的胜糖通道使得lysozyme像是muramidase而造成細胞溶解。而大部分的口腔細菌可以對抗溶解所以目前對溶解反應是否真會在人體內產生仍然存疑。Lysozyme可經由抑制細菌細胞壁上的呼吸系統或是活化細菌內生性的自溶酵素來殺死細菌。然而，lysozyme在唾液裡扮演最重要的抗菌角色應是聚集細菌使得他們無法黏附在口腔黏膜上。Pollack等人的研究指出lysozyme可與很多類型的S. mutans 黏附，唯不同類型的黏附速率不同 (見表20-2)。血漿類型a和b型可在12到15分鐘內被lysozyme完全黏附到飽和，而其他的種類可能需要三小時。在實驗室裡只需要50mg的lysozyme即可抑制血漿類型a和b型的生長，而其他種類需要20~100倍的濃度才能抑制(見表20-2)。這個發現可知在人體中血漿類型a和b型可被lysozyme抵抗消除，這呼應了人類牙菌斑裡這兩種類型的細菌濃度很低的事實。
對lysozyme有反應的S.mutans中，BHT種(serotype b)是最敏感的一種。BHT和其他種類不同的地方在於它有大量的lipoteichoic acid(LTA)。Iacona研究指出LTA是提供lysozyme黏結的重要因子，因此在牙菌斑裡鮮少看到血漿類型b種應是lysozyme的功勞。這種類型的細胞通常零星散落在唾液裡並且會很快的經由LTA接受器和lysoyme黏結，造成細胞聚集或是被吞下或是因為細胞膜上的呼吸酵素被抑制而死亡。以上的情況顯示出宿主有防止外來的mutans streptococci在牙齒表面聚集的抗菌能力。血漿類型a和b也因此被歸類為另一種類(S.cricetus 和 S.rattus)，分別是倉鼠和老鼠體內的主要細菌。
Lactoperoxidase (LPO)
Lactoperoxidase (LPO) is an enzyme found in the saliva which converts hydrogen peroxide formed by plaque bacteria to water and an oxidized product(s) (oxidants). These oxidants in turn react with sulfhydryl groups present in proteins, thereby forming disulfide bonds. If these sulfhydryl groups are at the active sites of bacterial enzymes, then enzyme functions, such as those involved in glycolysis, are inhibited. LPO can bind to hydroxyapatite and to various streptococci so that it is likely to be a component of plaque. Saliva contains thiocyanite ions (SCN), which can be oxidized by LPO, in the presence of hydrogen peroxide, to form the highly toxic hypothiocyanite radical (OSCN ). The amount of SCN- and LPO present in vivo is adequate to give rise to levels of OSCN-, which should be inhibitory for S. mutans and other acidogenic organisms. However, some plaques cannot generate sufficient amounts of hydrogen peroxide to drive the reaction towards OSCN- production. S. sanguis is known to produce hydrogen peroxide, leading to the surmise that plaques that are unable to form hydrogen peroxide are also low in S. sanguis. Plaques low in S. sanguis could be high in S. mutans and therefore, cariogenic in nature. This argument suggests that cariogenic plaques escape the inhibitory action of LPO by virtue of their inability to generate hydrogen peroxide.
Lactoperoxidase
Lactoperoxidase (LPO) 是種在唾液裡的酵素，它可以轉換牙菌斑裡細菌產生的氫和氧成為水或其他氧化產物 (氧化劑)。這些氧化劑可以和蛋白裡面的氫硫物質反應形成二硫化物。如果細菌酵素上的活性位子是氫硫基，那麼這個酵素的功能像是糖解(glycolysis)作用就會被抑制。LPO可以黏附在hydroxyapatite以及多種streptococci上而一起組成牙菌斑。唾液裡有thiocyamite離子(SCN)會被LPO氧化，在有二氧化氫的狀態下可以形成高毒性的hypothiocyanite自由基(OSCN-)。SCN-和LPO在人體中的數量可以使OSCN-濃度提高，抑制S.mutans和其他的耐酸性細菌。然而有些菌斑沒有足夠的二氧化氫來形成OSCN-。我們知道S.sanguis可以形成二氧化氫所以可以推測無法二氧化氫的菌斑裡S.sanguis占的比例不高。當菌斑裡的S.sanguis占的比例不高，S. mutans就會較高，也就比較容易蛀牙。這個結論指出易蛀牙的菌斑裡二氧化氫產量少，即不易被LPO抑制。
Lactoferrin
Lactoferrin is a salivary glycoprotein which exerts an antibacterial action through its ability to bind iron so avidly that it essentially depletes the environment of this mineral. Iron is an essential nutrient for most bacteria and accordingly, these organisms fail to multiply and are either cleared from the mouth via swallowing or are neutralized by other host defense mechanisms. There is no evidence that lactoferrin is important in caries prevention. Mandel has observed that lactoferrin levels in saliva and plaque do not differ between caries resistant and susceptible subjects. In vitro lactoferrin is bactericidal for S. mutans by virtue of its ability to chelate cell-associated iron. S. salivarius and S. mitior are not as susceptible, presumably because the lactoferrin does not bind as efficiently to these organisms. This raises the possibility that schemes for optimizing the anti-S. mutans action of lactoferrin can be devised similar to what has been done for the LPO system.
Lactoferrin
Lactoferrin是種唾液裡的糖蛋白，他的抗菌作用來自於和鐵離子的黏結能力很強使得鐵離子減少。鐵是多數細菌的必需營養來源，所以當鐵缺乏時，細菌就不能增生，容易被吞下或是被宿主抵抗機制中和。Lactoferrin並沒有直接證據顯示可以抗蛀牙。Mandel觀察到在不易蛀牙與易蛀牙的個體裡，lactoferrin在唾液和菌斑裡的濃度都沒有差別。在實驗室，lactoffrin可以藉由與鐵結合的能力來抑制S. mutans。而對S.salivarius和S. mitior就沒有這麼好的抑制能力可能是因為lactoferrin對它們的黏結能力較差所致。以上可推論lactofettin的抗S. mutans機制可如同LPO系統般運作。
Salivary Adhesins
The high-molecular-weight glycoproteins (mucins), which adsorb to the tooth surface to form the acquired enamel pellicle (AEP), promote the colonization of S. sanguis but not S. mutans (See "The First Colonizers" in Chap. 6). The relative paucity of sites specific for S. mutans on the AEP comprises a host defense mechanism against S. mutans colonization. There now is evidence that these or other glycoproteins do bind S. mutans, but that when this binding occurs in solution, S. mutans becomes aggregated in such a manner that its chances of colonizing a tooth surface are greatly reduced. This would constitute another mechanism by which the host could clear organisms rapidly from the mouth. This phenomenon has been studied in regard to S. mutans' ability to bind to solid surfaces in the presence of saliva. Magnusson and Ericksson investigated the in vitro attachment of a serotype c strain of S. mutans to powdered hydroxyapatite (HAP) in a system involving S. mutans, HAP and saliva. Incubation of the saliva with S. mutans prior to the addition of HAP consistently gave lower adsorption of S. mutans, compared to the situation where the three components were mixed simultaneously. This suggested that some component in the saliva interacted with S. mutans, so as to reduce its ability to bind to HAP.
Clark and Gibbons, studied the adsorption of tritium-labeled cells of S. sobrinus (strain 6715, serotype g) to HAP disks. The disks were suspended in either saline or saliva containing about one hundred million S. mutans CFU per ml. The amount of radioactivity retained on the disks after washing reflected the amount of bacterial adsorption. In this model system the adsorption of S. mutans was logarithmically related to cell concentration, with equilibrium reached after 45 minutes of incubation. Only a small percentage of the streptococci became attached, and the adsorped cells occupied about three percent of the available surface area on the disks. This behavior would seem to mimic the weak adsorption of S. mutans to the teeth that is observed in vivo.
Maximum adsorption of S. mutans occurred when cells and disks were suspended in saline (Table 20-3). If the disks were pretreated with saliva, fewer cells adsorped. But if the disks were pretreated with saliva and then both the disks and the bacteria were suspended in saliva, there was a 30-fold reduction in adsorption (Table 20-3). The addition of sucrose to the suspension fluid, so as to permit synthesis of glucan during the attachment period, did not improve adsorption. Even when the cells were pretreated with sucrose, so as to have glucan already on their surfaces, there was no improvement in adsorption. The attached cells were weakly bound to the HAP, as most could be desorped either by saline or saliva (Table 20-3). As the saliva was obtained from a single individual who presumably had no unique caries background, the inference is that saliva contains a factor(s) which seriously compromises the ability of in-vitro-grown strains of S. mutans to attach to HAP. This is in agreement with clinical studies which demonstrated the great difficulty related to the implantation in humans of in vitro-grown S. mutans (See "S. mutans Colonization" in Chap. 6).
唾液黏結
唾液黏著劑
高分子量的醣蛋白(mucins) 會被牙齒表面吸收成為acquired enamel pellicle (AEP)，AEP可以促進S. sanguis而不是S. mutans的菌落聚集(見第6章 “The First Colonizers”)。這樣相對少量可以讓S. mutans黏結在AEP上的位子，可看做是一種宿主對抗S. mutans的機制。現在有證據指出這些或其他的醣蛋白的確會和S. mutansr黏結，而當這種黏結在溶液裡產生時，S. mutans會彼此聚集因此就降低了S. mutans黏附在牙齒上的機會。這形成了另一個機制使宿主得以快速的清除這些外來菌。此現象如同在唾液裡S. mutans黏附在堅硬表面上，因此許多研究著重於S. mutans黏附在表面的能力。Magnusson和Ericksson發現在體外實驗裡，血漿類型c的S. mutans 和粉末狀的hydroxyapatite (HAP)黏結是一個系統，這系統包括了S. mutans，HAP和唾液。S. mutans在唾液裡培養之後再加入HAP產生的S. mutans, HAP系統黏結會比一開始就讓三者混合來得低。這說明了唾液裡有某些物質會降低S. mutans黏附到HAP上的能力。
Clark和Gibbons研究用氚標出S. sobrinus內細胞 (strain 6715, serotype g)黏附在HAP圓盤碎片上被吸收的情形。HAP圓盤碎片懸浮在含有十億個S. sobrinus CFU每毫升的生理食鹽水或是唾液裡面。圓盤碎片上有X光不透性物質，清洗過後可以清楚見到上面黏附的細菌，借以觀察吸收黏附的情形。在這個實驗的狀況下，經過45分鐘的培養，S. mutans的吸收和細胞含量成正比。只有少量的鏈球菌會聚集在一起，而黏附被吸收的細菌大約佔據了圓盤碎片表面積的3%。S. mutans只有少量被黏附吸收情形和在口內黏附吸收到牙齒上的狀況很像。
當細胞和圓盤碎片是懸浮在生理食鹽水裡的時候，細菌會達到最多的黏附吸收(表20-3)，如果園盤碎片被唾液浸潤，細菌黏附吸收率就降低。但如果圓盤碎片被唾液浸潤而細菌和圓盤碎片同時懸浮在唾液裡，吸收率會降低約三十倍(表20-3)。另外添加蔗糖到懸浮液裡，讓肝醣得以同時形成，並不會增加對吸收率。即使先用蔗糖處理過細菌使表面帶有肝醣，也不會增加吸收率。這些細胞和HAP的黏結力很低，不論在生理食鹽水或唾液裡都不太會黏附吸收(表20-3)。這唾液樣本來自於一個沒有特殊蛀牙情況的個體，表示唾液裡含有某些因子可有效的阻斷S. mutans和HAP的黏結，以上的結論以及臨床實驗都證實S. mutans植入人體內生長是非常困難的。(見”S. mutans 菌落”於第6章)
Other studies have shown that lectin-like interactions mediate the attachment of certain oral bacteria to oral epithelial cells. A characteristic of lectin-like reactions is that they can be inhibited by one or more low molecular weight sugars which attach firmly to the binding site on the protein (lectin). These sugar-lectin interactions are highly specific, as each lectin receptor site will recognize only a single sugar or closely related structures.
Various low-molecular-weight compounds were evaluated for their ability to inhibit the adsorption of the S. mutans serotypes to salivary-coated HAP disks. Adsorption of all serotypes was inhibited by galactose and melibiose but not by 16 other related compounds (Table 20-4). Both galactose and melibiose contain an alpha galactoside residue, whereas, lactose which has a beta galactoside residue was without any effect. This indicates that the lectin capable of binding all serotypes of S. mutans recognized an alpha galactoside residue on the surface of S. mutans. Certain amine configurations also inhibited the adsorption of S. mutans. Thus, spermine (a polyamine) inhibited the adsorption of all serotypes, whereas mannosamine inhibited serotypes a,d and b, and galactosamine inhibited serotypes a,c and e. Iodoacetate was effective against all serotypes (Table 20-4). The ability of galactose, spermine and iodoacetate to inhibit the adsorption of S. mutans to HAP raises the possibility that these compounds could be used in vivo to prevent the colonization of teeth by S. mutans.
其他的研究發現lectin-like的反應是某些口腔細菌和口腔上皮黏膜細胞黏附的媒介，lectin-like反應主要是藉由蛋白質(lectin)上的位子使一個或多個低分子量的糖分子和它們緊密鍵結來達到抑制細菌和口腔上皮黏附。這種糖-lectin反應是具有高度獨特性的，每個lectin的接收點只會辨認出一個單一糖分子或是結構類似的分子。
許多低分子量的化合物被用來評估他們對於抑制S. mutans血漿類型到有唾液包覆的HAP圓盤碎片，galactose和melibiose可以抑制所有血漿類型的黏附吸收而其他16種結構類似的化合物就不行(表20-4)。Galactose和melibiose都有一個alpha galactoside反應存留物，然而，lactose的bata galactoside反應存留物就沒有太大的作用，這指出lectin可以和所有表面有alpha galactoside反應存留物的S. mutans鍵結，不論是哪種血漿類型。有些氨基化合物也會抑制S. mutans的吸收。因此spermine(一種polyamine)抑制所有類型的吸收而mannosamine抑制血漿類型a,d和b而galactosamine抑制血漿類型a, c 和 e，Iodoacetate則對任何類型都有效(表20-4)。Galactose, spermine 和iodoacetate對S. mutans黏附HAP的抑制能力可用來防止S. mutans在人體裡黏附牙齒組成菌落。
Salivary Proteins
The host has several salivary proteins which exhibit an anti-S. mutans effect. If these proteins encounter S. mutans that is free in solution, they can cause aggregation of this organism which results presumably, in the exit of S. mutans from the mouth via swallowing. This is probably the major mechanism which the host has for removal of S. mutans. This system can be enhanced by adding to the oral environment those sugar molecules that bind to either lectin-like receptors on the surfaces of the bacteria or on the acquired enamel pellicle. In either case, they would reduce the adsorption of S. mutans by blocking those attachment sites necessary for adsorption. If these proteins attach to already adherent cells of S. mutans, then their protective effects are less. However, if they have bactericidal action, such as possessed by lysozyme, lactoperoxidase or lactoferrin, then some degree of microbial killing could occur. Of these mechanisms, the lactoperoxidase system is open to manipulation by the usage of exogenous enzyme systems which generate hydrogen peroxide.
唾液蛋白
宿主有很多唾液蛋白可以抗S. mutans，在S. mutans自由懸浮在液體裡的情況下這些蛋白可以造成細菌聚集使得細菌被吞下然後離開口腔，這大概是宿主移除S. mutans細菌最主要的機制。這機制可藉由在環境中加入蔗糖分子使它們與細菌表面上的lectin-like接收器鍵結或是後天的enamel薄膜來提升。無論哪種情況，它們都可以藉由占據鍵結位子來降低S. mutans的黏結吸收，但如果這些蛋白質黏附在已經鍵結的S. mutans上，那抑制的效果就會降低。然而，如果蛋白質有殺菌的作用像是lysozyme, lactoperoxidase或lactoferrin，仍然可以達到某種程度的殺菌。在這些機制裡面，lactoperoxidase系統是由外來酵素系統使用後產生了二氧化氫來完成。
SPECIFIC MECHANISMS. THE IMMUNE SYSTEM.
The SPH invites speculation about the role which the immune system might play in dental diseases. If a limited number of bacterial species initiate caries, then it may be possible to identify mechanisms of immunity against these organisms in disease-free people, and thereby develop means of actively immunizing other individuals who are at risk to dental disease. Both are formidable tasks. The obvious association of S. mutans with human decay has caused the recent interest in vaccination as a means of caries control. In this chapter we will describe the results obtained with vaccination experiments involving S. mutans and discuss the findings in the context of plaque microbial ecology.
專一機制 免疫反應
SPH引起免疫反應在牙科疾病裡扮演何種角色的推論，如果很少種類的細菌可導致蛀牙，那麼在沒有蛀牙的人身上就很容易找出哪種免疫機制阻擋了這疾病，進而可以知道用甚麼免疫方法可以用來預防高危險群的人罹病，然而這些現實上都很難達成。S. mutans和蛀牙的明確關係引起近年來用疫苗來控制感染的想法。在這個章節裡我們會討論對抗S. mutans的實驗性疫苗結果以及在牙菌斑裡微生物組成及生態。
Immune Globulins
Hosts have specialized cells and organs, collectively referred to as the immune system, which recognize non-self chemical structures. This recognition causes the immune system to synthesize antibodies of exquisite specificity against the foreign compound or cell which usually results in the destruction or neutralization of the interloper. This acquired information is then stored in a memory-like fashion so that it can be rapidly retrieved and amplified when the foreign body is again encountered. Antibodies can be either cellular or protein in nature. Immunity against dental caries, as it currently is understood, is mediated primarily, if not exclusively, by globular proteins known as immunoglobulins which circulate in the blood stream and to a lesser extent are present in secretions.
Five immunoglobulins have been identified and given the designation IgG, IgA, IgM, IgD and IgE. Only the major immunoglobulins, i.e., IgG, IgA and IgM have been implicated in immunity to caries. Some of the characteristics of these immunoglobulins are given in Table 20-5. IgG comprises about 80 percent of the total immunoglobulins, but is found in low levels in secretions such as saliva. Its concentration in gingival crevice fluid obtained from sites of dental inflammation is high (Table 20-5). However, the gingival crevice fluid flow in the absence of inflammation is low and may amount to only a few ml per day. IgG exerts its antimicrobial activity in conjunction with phagocytic cells, complement and platelets, all of which are in small supply on the dental surfaces. Nevertheless, there is data from both man and monkeys which suggest a role for specific IgG antibody to S. mutans in immunity against dental decay.
免疫球蛋白
宿主有特別的細胞和器官，統稱為免疫系統，它可以辨認出非自身的化學結構。這個辨識可以造成免疫系統合成靈敏的抗體對抗造成破壞的外來化合物或細胞。這些資訊會像記憶般被儲存，當外來物再度進入，它可以很快的辨識並且製造抗體。抗體可以細胞或是蛋白質的形式存在。對於蛀牙的免疫，就目前所知，主要是血液循環中的球蛋白又叫做免疫球蛋白。
目前發現有五種免疫球蛋白，分別取名為IgG, IgA, IgM, IgD和IgE。只有主要的球蛋白例如IgG, IgA, IgM與蛀牙免疫相關。這些免疫球蛋白的特性列在表20-5。有80%的免疫球蛋白是IgG，但IgG在唾液裡的含量很低，只在有牙齒發炎反應發生的時候，IgG在牙齦溝液中含量會增高(表20-5)。而在沒有發炎狀態下，牙齦溝液中的含量就很低，大約一天只有幾個毫升。IgG和巨噬細胞(phagocyte)，補體(complement)還有血小板(platelets)會互相配合達到抗菌效果，這些物質在牙齒表面都很少。然而有研究顯示同時在人和猴子體內都發現有種特殊的IgG抗體會特別針對S. mutans產生免疫效果，避免蛀牙。
IgA antibodies are found in elevated amounts in secretions such as saliva and are not dependent upon serum components for their ability to provide immunity. They need only to coat or agglutinate bacteria in such a way that the microbes cannot adhere to surfaces such as the teeth. IgA antibodies are synthesized by the plasma cells found in the various salivary glands. They are dimerized with a J-chain prior to release from the plasma cell and then acquire an additional protein called secretory component as they pass through the secretory epithelial cell. This configuration renders the secretory or S-IgA molecule resistant to proteolysis so that it is well designed to operate in an environment containing microbial proteases. S-IgA antibody to S. mutans is associated with immunity to caries in man and in rodents.
IgM antibodies, so named because of the macro size of this immunoglobulin, do not appear to be important in caries immunity. However, in cases of selective IgA deficiency, IgM antibodies to S. mutans are found in the saliva and are associated with some degree of protection against dental decay.
IgA抗體在分泌物當中含量高，像是唾液，並且它不需要依靠其他的血漿因子來達到免疫的效果。它們只需要包覆或是凝結細菌使細菌無法和表面(例如牙齒)黏結。IgA抗體是由漿細胞合成，出現在很多分泌性唾腺裡，它們有兩個化合物，在被漿細胞釋出前會有一個J-chain，然後需要結合一個額外的蛋白質叫做分泌因子，之後再一起通過分泌上皮細胞。這樣的結構使得分泌性或是S-IgA分子可以抵抗蛋白質水解可以在有蛋白質溶解酵素內的環境裡作用。S-IgA抗體在人類和嚙齒類對S. mutans有免疫的作用。
IgM抗體得名來自於這種免疫球蛋白很大，對於抗蛀牙並沒有扮演重要角色。然而，在選擇性IgA缺乏的情況下，在唾液裡會發現有IgM康體可對抗S. mutans防止蛀牙。
Presence of Specific Antibody(ies) to S. mutans in Human Sera and Saliva
Human sera contain specific antibodies against many indigenous bacteria. The presence of these antibodies does not mean that any organism(s) under investigation was associated with an infection, or that these antibodies are protective against a new infection by the organism. In order to draw a conclusion concerning the former, the antibody levels would have to be determined before, during and after an infection; whereas the latter would require evidence showing that an elevated titer of specific antibody coincided with the disappearance of symptoms, or was able to prevent a new infection by the specific organism. These types of data are not available for S. mutans. Research is at an early stage, concerned with the documentation of specific antibody to S. mutans in individuals of varying caries experience. This data must be interpreted cautiously because caries experience, as measured by the classic DMF score, is a morbidity index, and is inadequate in describing whether decay is currently active or whether the individual has been, or still is, subjected to the challenge of the disease determinants, i.e., sucrose, S. mutans, low fluoride, etc. This information is necessary in order to assess the significance of the antibody levels. In the succeeding discussion we will define the caries status of the individuals as caries-free, i.e., DMF score = 0; caries inactive, i.e., MF score greater than one; caries active, i.e., D score greater than one; in order to have diagnoses corresponding to no infection, post infection and infection.
在人類唾液和血漿中出現S. mutans特定的抗體
人類血漿有很多對抗原生性細菌的特殊抗體，出現這些抗體並不意味著生物體受到感染或抗體要對抗新的感染。為了要區別受到感染和正常的不同，必須知道感染前中後抗體的濃度，為了要區別是否有新感染，需要檢測症狀消失是否是由於特殊的抗體濃度升高或是有特殊的生物體可以避免感染發生。S. mutans的這些資料都無法取得。研究目前都停留在很早期的階段想證明不同蛀牙經驗的個體內有不同的抗S. mutans抗體。這些資訊必須小心的解讀因為蛀牙經驗像是DMF指數是個發病指數並不足以提供蛀牙目前的活躍性，也無法知道個體曾經或正在有患病因子(例如蔗糖，S. mutans和低氟環境)的環境下。這些資訊對於評估抗體的的濃度很重要。在接下來的討論裡我們會定義個體的蛀牙狀態像是無蛀牙情況下 DMF值等於0; 蛀牙不活躍, MF值大於1 ; 蛀牙活躍, D值大於1，這些都是為了分辨無感染，感染中或感染後。
Cross-sectional Studies
Caries-Free Individuals: In populations which are isolated and/or have low sucrose diets, the absence of caries may be due to the absence of a cariogenic infection, an undefined genetic-based resistance, or the presence of protective antibodies against a cariogenic flora. Animal studies indicate that caries-free animals usually had not been sufficiently challenged by sucrose and S. mutans. When they were properly infected with S. mutans, they developed caries, thereby discounting the role of a genetic factor or an immunological factor in their caries-free state. By analogy, and the obvious susceptibility of isolated peoples, i.e., Eskimos, Polynesians, Indians, etc., to caries when sucrose is added to their diets, one would suspect that the human caries-free state also reflects an insufficient cariogenic challenge rather than an immunologic or genetic component.
Cross-sectional 研究
無蛀牙的個體: 飲食中只有很少或是沒有蔗糖，沒有蛀牙可能是因為沒有蛀牙性感染，未定義的基因抗蛀性，或是有保護性的抗體
Cross-sectional Studies
Caries-Free Individuals: In populations which are isolated and/or have low sucrose diets, the absence of caries may be due to the absence of a cariogenic infection, an undefined genetic-based resistance, or the presence of protective antibodies against a cariogenic flora. Animal studies indicate that caries-free animals usually had not been sufficiently challenged by sucrose and S. mutans. When they were properly infected with S. mutans, they developed caries, thereby discounting the role of a genetic factor or an immunological factor in their caries-free state. By analogy, and the obvious susceptibility of isolated peoples, i.e., Eskimos, Polynesians, Indians, etc., to caries when sucrose is added to their diets, one would suspect that the human caries-free state also reflects an insufficient cariogenic challenge rather than an immunologic or genetic component.
Cross-sectional 研究
無蛀牙的個體: 飲食中只有很少或是沒有蔗糖，沒有蛀牙可能是因為沒有蛀牙性感染，不明確的抗蛀基因，或是有保護性的抗體。動物實驗指出無蛀牙的個體是未受到蔗糖或是S.mutans的足夠的挑戰，如果他們被S.mutans ”適當” 感染後還是會出現蛀牙的情形。因此基因和免疫力這兩個因子可能並不能擔任持續無蛀牙狀態這樣的角色。根據這樣的類比，有些如易蛀牙的人種像是愛斯基摩人,玻里尼西亞人,印度人等等會蛀牙是因為飲食內有了蔗糖這樣的蛀牙因子，因此我們也可以合理懷疑沒有蛀牙的人可能反映出飲食內沒有足夠致齲物的挑戰而不是因為有抗蛀的免疫或基因因子。
Table 20-6
Antibody Titers (Log2) to Streptococcus mutans in Individuals of Varying Caries Activity
Antibody Class
Serum Saliva
Subjects DMF IgG IgA IgM IgA
Naval Recruits (18-19 yrs)a
CF Caries Free (n=26)
HCA High Caries Active (24)
0
>15
4.5}
4.2}
Young Children (2.5-5.5 yrs)b
RCA Rampant Caries (15)
HCA Caries Active (12)
11.5
5.1
1.8
2.7
0.7
0.4
1.3
0.9
1.8
1.9
Young Adults (18-14 yrs)c
LCI Low Caries Inactive (34)
HCI High Caries Inactive (31)
HCA High Caries Active (31)
2.9
17.6
17.2
5.8
3.9
5.3
4.0
4.1
4.2
5.2}
3.7}
4.3
4.5
6.2
4.5
} Significant difference
value in box was significantly different from other values in column.
a) adapted from Kennedy et al., 1968. Archs. Oral Biol. 13:1275. Log2 titers calculated from agglutination titers shown for strain SL1 (serotype d).
b) adapted from Lehner et al., 1978. Archs. Oral Biol. 23:1061. Serum antibodies measured by indirect fluorescent technique. Salivary antibody by agglutination.
c) adapted from Challacombe, 1980. Archs. Oral Biol. 25:495. Antibodies measured as in b.
Nevertheless, there do exist a few individuals who ingest modern-type diets, and reach adult age caries free. These individuals tend to have elevated levels of specific antibody against one or more serotypes of S. mutans when compared to levels present in caries-active subjects. For instance, caries-free naval recruits had higher agglutinin titers to S. mutans that did similar-aged recruits with rampant caries (Table 20-6). The magnitude of this difference was not great and raises the question as to how a certain level of serum antibody could be protective in the caries-free population, but be of no apparent value in a high-caries-active population. One explanation could be that the antibody measured by an agglutination assay is not a protective antibody and merely indicated that the host's immune system had been exposed to S. mutans. This latter possibility is supported by the almost universal occurrence of S. mutans in human mouths.
然而，有些人在攝取現代的飲食下到了成人還是沒有齲齒。這些人和有齲齒的人比起來傾向於對一種或多種S. mutans有特殊的抗體。例如，海軍招募時無齲齒的人比起同年紀有齲齒的人就有比較高的抗體凝集含量(Table20-6)。這差異並不顯著，不過讓人想知道多少含量的血清抗體可以保護無蛀牙個體免於蛀牙。一種解釋是抗體凝集試驗做出來的可能不是保護性的抗體，只是宿主免疫系統對抗S. mutans的反應。後面的可能較被支持的，因為幾乎所有人口中都有S. mutans。
Infants are exposed to S. mutans present in the mouths of their family members, and some teeth become demonstrably colonized shortly after their eruption. An immune response, measured by agglutinating antibodies to cell walls of S. mutans, appears to be age related (Table 20-7). Fourteen percent of the sera obtained from infants under six months of age exhibited a positive reaction with various S. mutans serotypes and three percent had high titer antibodies. This is surprising, given the edentulous nature of these infants and the apparent need of a solid tooth surface for effective colonization of S. mutans. Could these early strong reactors represent that segment of the population which remains caries free or low caries inactive? Studies which identify these children in infancy and then follow them through the caries-prone years are necessary in order to answer this question.
嬰兒在出生幾個月後就會因為家中成員而有S. mutans，出現牙齒後不久S. mutans就會附著在牙齒上。有一種免疫反應似乎和年齡相關，他是檢驗S. mutans細胞壁上的抗體是否會產生凝集(Table 20-7)。14%的六個月嬰兒血漿就對多種S. mutans有反應而其中3%有高濃度的反應。這發現很驚人，因為表示S. mutans可以無牙脊上聚集。有這些早期的抗體反應的人可以因此而無齲齒或是齲齒活性很低嗎?必須要做研究這樣的嬰兒長到容易齲齒的年紀後才能有答案。
Table 20-7
Number and Percentage of Cell Wall Agglutination Reactions to Four S. mutans Strains (BHT serotype b, SL-1 (d), 20, 10557 (c)) by Sera from Children of Five Age Groups
Under 6 mos 6 mos - 3 yrs 3 - 6 years 6 - 12 years 12 - 16 years
No. % No. % No. % No. % No. %
Negative 152 86 165 72 108 59 149 58 96 46
Positive (a) 25 14 65 28 76 41 109 42 111 54
Strong positive (b) 6 3 7 3 7 4 25 10 27 13
(a) titers ≥ 1/20 (b) titers ≥ 1/80
Adapted from Berkenbilt and Bahn 1971, JADA 83:332.
But how would neonates acquire this "immunity"? Some understanding in this regard was provided by experiments which showed that the oral administration of various vaccines led to increased titers of specific IgA antibody in tears, saliva and colostrum. In other experiments gnotobiotic rats were fed formalin-killed S. mutans (serotype g) in their food. These animals demonstrated elevated salivary and colostrum IgA titers to serotypes g and a strains of S. mutans, and were able to resist a subsequent cariogenic challenge with a serotype g strain of S. mutans. The presence of specific antibodies to S. mutans in the colostrum suggested that immunity to S. mutans could be passively transferred by means of mother's milk. This was confirmed by studies in which bovine milk containing antibodies to S. mutans was shown to significantly reduce the numbers of carious lesions in rats fed this lyophilized milk and challenged with the homologous (same serotype) S. mutans strain.
但是新生兒的"免疫"從那裏來?有些實驗顯示由口腔給予多種疫苗可以增加眼淚，唾液和初乳中某些特殊的IgA抗體。其他的實驗，把無菌老鼠用無菌的食物(含福馬林可殺死S. mutans (serotype g))餵養，這些動物在唾液和初乳中的IgA含量增加，因此可以對抗S. mutans (serotype g)。這樣特別的抗體被認為可以由母乳傳遞給嬰兒，也有實驗證明。用含S. mutans抗體的牛奶餵老鼠，顯示這樣的老鼠齲齒率有顯著性的降低。
Some infants may become passively immunized in the neonatal period if their mother's milk contains high levels of secretory IgA and probably IgG antibody to S. mutans. This possibility could account then for the three percent of the infants who exhibited a strong positive reaction to S. mutans, (Table 20-7) and perhaps for that small segment of the population that is caries free. This phenomenon of passive immunity is being investigated as one of the tactics that can be used for the delivery of an anticaries vaccine (See "Human Vaccines" in this chapter).
有些嬰兒會在新生兒時期有母奶中的高含量分泌性IgA和 IgG而有了被動的免疫能力。這可能解釋了3%的新生兒對S. mutans 有很強的反應 ( Table 20-7)也解釋了某些人是無齲齒的狀況。這現象裡被動的免疫反應可用在給新生兒抗齲齒的疫苗概念上(詳見本章中的"Human Vaccines")
Caries-Active Individuals: Decay (D) Greater Than 1
These individuals have open lesions and/or are in the process of developing new lesions. If an immunological response is involved, these individuals would be expected to exhibit elevated antibody levels to S. mutans. The number of decayed surfaces or teeth would appear to be the most reliable indicator of the magnitude of the antigenic challenge. However, 2.5- to 5.5-year-old children with rampant caries (greater than 10 carious surfaces) and those with one or more lesions had comparable levels of serum IgG, IgA and IgM antibody, as well as salivary IgA antibody (Table 20-6). Serum IgM antibody showed a significant positive correlation with the DMFS score and this was thought to reflect the antigenic load experienced by the child. Other than this observation, there was little evidence of a protective immune response to active decay in these children.
齲齒活躍的個體 : 齲齒(D)大於1
這些個體有病灶或是正在產生新的病灶。如果有免疫反應介入，這些個體對S. mutans的抗體反應會提高。齲齒的表面數和顆數是有抗原反應最好的指標。然而，2.5歲到5.5歲的有猛爆性齲齒的孩童(大於十個蛀牙表面)和只有一個或幾個病灶的比較起來，前者的血清中IgG, IgA和IgM抗體還有唾液裡的IgA抗體含量高(Table20-6)。血清IgM抗體和DMFS有顯著的正相關，且被視為可反映出孩童身上抗原性。除此之外，在這些孩子身上有很少的證據顯示有保護性的免疫反應。
Caries-Inactive Individuals: Missing and Filled (MF) Teeth Greater Than l
The overwhelming majority of people ingesting sucrose-containing diets develop caries. If these lesions are treated and the individual develops no new lesions in the succeeding years, he is considered to be caries inactive. Could this absence of caries reflect an immune state in which the individual has developed protective antibodies as a result of his prior infection? This is difficult to ascertain from the available cross-sectional information. The caries-inactive individual may have missing and/or filled teeth (MF score) which range in number from one to over 30. The titers of specific serum antibody against S. mutans antigens is significantly higher in the low MF subjects than in the high MF subjects. This negative correlation suggests that the low MF individuals were able to mount and sustain an effective immune response against S. mutans, whereas the high MF subjects did not. Why this variation in immune response to the same organism? Why did the high MF subjects, who presumably had the highest antigenic exposure, exhibit the lower response of IgG antibody? What role might salivary antibodies play in this protection or lack of protection?
齲齒不活躍性個體: 失去或是填補(MF)牙大於1
大部分的人吃了含蔗糖的飲食都會產生齲齒，如果這些病灶被治療了而這些人之後也沒有新的齲齒，就被認為是齲齒不活躍性的個體。這樣沒有齲齒的狀態是因為免疫系統產生了保護性的抗體嗎?這問題很難就cross-section的資料來加以回答。齲齒不活躍性個體可能有失去或是被填補的牙齒(MF 數可從1~30)。對抗S. mutans的特殊血漿抗體在低MF的人身上比較高。這樣的負相關解釋了低MF的人可以對S. mutans產生有效的免疫反應而高MF的人沒有辦法。為什麼在同樣生物體中會有不同樣的免疫反應呢? 為什麼在高MF個體裡應該有高抗原卻只有引發低抗體反應呢? 唾液性抗體是否扮演保護性角色還是根本不具保護性呢?
Antibodies to S. mutans and S. sanguis were examined in serum and parotid saliva of 96 young adults. The subjects were divided into three groups: 1) a low caries-inactive (LCI) group that had seven or less missing or filled teeth; 2) a high-caries-inactive (HCI) group that had 13 or more filled or missing teeth; and 3) a high-caries-active (HCA) group that had 13 or more DMF teeth and between one and four approximal lesions which extended into the dentin (Table 20-6). The LCI and HCA groups had similar antibody profiles, despite their dissimilar clinical backgrounds. Both differed from the HCI group in having significantly higher titers of serum IgG antibody and significantly lower titers of salivary IgA antibody (Table 20-6).
在96個年輕人的血漿和腮腺唾腺中檢驗對S. mutans和S. sanguis 的抗體反應。將他們分成三組: 1) 小於或等於7顆失去或填補牙的屬於低齲齒活性組(LCI) ; 2) 13顆以上失去或填補牙的屬於高齲齒低活性組(HCI) 還有3) 13顆以上DMF牙和1~4個鄰接面到牙本質的蛀牙屬於高齲齒活性組(HCA)(Table 20-6)，LCI和HCA雖有不同的臨床狀態但有相似的抗體濃度反應。他們都和HCI不同，有高濃度的血漿中IgG抗體和低分泌性IgA (Table 20-6)
These paradoxical findings were explained via an interesting hypothesis. The elevated serum IgG and IgM titers in the LCI subjects are indeed protective. For some reason, possibly genetic in origin, these LCI subjects were able to mount and maintain an effective immune response to S. mutans for long periods of time. The key word here is "maintain", as the HCA patients were also able to mount an antibody response to S. mutans, but when the carious lesions were treated these antibody titers dropped to levels which were no longer protective. Accordingly, the HCA patient became an HCI subject who could continue to develop new carious lesions whenever S. mutans regained ascendancy in the plaque.
這樣似是而非的發現可以用一個很有趣的假說解釋。在LCI組中提升的IgG與IgM的確是有保護性的。因為一些原因，也許是基因，這些LCI個體可以有效並長期維持對S. mutans的免疫反應。這裡的關鍵字是"維持"，HCA組可以有S. mutans抗體反應但當齲齒病灶時抗體反應降低到不再有保護效果。因此，當S. mutans 在牙菌斑中變得有優勢時，HCA就繼續產生新的齲齒病灶然後變成HCI。
No role for salivary IgA in caries protection was proposed in this hypothesis, probably because the low levels of IgA in the LCI subjects could not be correlated with low caries experience. However, the high levels of salivary IgA antibody in the HCI individuals could reflect a mechanism by which S. mutans was cleared from the oral cavity, and this in turn could be responsible for the caries-inactive status of these individuals. Thus, this data permits a role for both serum IgG and salivary IgA in caries protection against S. mutans. No immunological documentation could be found for the involvement of S. sanguis in the carious lesion.
在這個假說裡並沒有唾液性IgA保護抗蛀，可能因為LCI個體中低濃度的IgA無法和低齲齒相關。然而，HCI個體中唾液高濃度的IgA能反應S. mutan從口中清除也可以成為齲齒不活躍的機制。因此，這些資料證實血漿中IgG和唾液中IgA對S. mutans有抗齲作用。但沒有資料可以顯示S. sanguis在齲齒病灶內有影響
Patients with an Immune Deficiency. Considerable information concerning the functions and interactions of the various components of the immune system has been obtained from individuals who possess one or more immune deficiencies. Selective IgA deficiency is the most common form of immune deficiency occurring at a frequency of about one in every 600 to 700 individuals. Arnold and his colleagues compared the caries status of 29 patients with IgA deficiencies with the ability of the patient's saliva to agglutinate the various serotypes of S. mutans (Table 20-8).
有免疫缺失的病人
這些人就的免疫系統裡有一個或多個的缺失，造成免疫系統間的關係或是功能產生異常。選擇性的IgA缺失是最常見的免疫缺失，發生率大約是六、七百分之一。Arnold等人比較了29個有IgA缺失的人唾液抗體對抗多種S. mutans的齲齒狀況，
Table 20-8
Effect of IgA Deficiency With and Without IgM Compensation on Salivary Agglutinin Titers to S. mutans and on Dental Caries Morbidity
Immune Status
IgA Deficient
Normal IgA IgM Compensation No IgM Compensation
No. of Subjects 31 11 18
Parotid Agglutinin Titer (Log2)
S. mutans
serotype a
b
c
d
e
g
5.8
3.4
5.3
5.5
6.5
3.3
6.3
3.5
7.1
6.3
5.8
2.2
<1
<1
<1
<1
<1
<1
Dental Caries Incidence Relative to Normal
DMFT
DMFS 0
0 -1.7
-3.6 + 6.9
+ 21.6
Adapted from Arnold et al., 1977. Clin. Immun. Immunopathol. 8:475; Arnold et al., 1978. Adv. Exp. Med. Biol. 107:401-410; McGhee and Michalek 1981. Ann. Review Microbiology.
In certain instances of IgA deficiency the IgM class of antibodies compensated for the missing IgA. This IgM antibody resembled secretory IgA in that it was synthesized locally at the mucosal surfaces, had both the secretory component and J chain, and was similar to secretory IgA in its secretory dynamics. Eleven of the patients had IgM compensation in that their saliva exhibited significant agglutinin titers to the six S. mutans serotypes. These IgM-compensated patients had DMFT and DMFS scores that were similar to the normal individuals (Table 20-8).
在某些IgA缺失的情況裡會有IgM類抗體來彌補遺失的IgA。IgM抗體很像是分泌性IgA，在黏膜表面合成，都有分泌的成分和J鏈，和分泌性IgA一樣。11個病人在唾液裡有IgM補償，對
六種S. mutans有顯著的凝集反應。這些有IgM補償病人的DMFT和DMFS和正常人差不多(Table 20-8)
The 18 IgA deficient patients with no IgM compensation had no demonstrable agglutinin activity to S. mutans and had about seven more DMF teeth and 22 more DMF surfaces than the normals and the IgM-compensated patients (Table 20-8). These data indicate that in the absence of specific s-IgA antibody to S. mutans in the saliva, there is a high level of dental morbidity.
有18個IgA缺失的病人沒有IgM補償對S. mutans沒有凝集反應，大約比正常人和有IgM補償有多於7個DMF和22個DMF的表面(Table 20-8)。這些資料顯示在唾液裡缺失了對S. mutans特殊的s-IgA抗體，會容易造成牙齒的病態。
Longitudinal Studies. A limitation of the previous investigations was their cross-sectional nature. A single antibody titer does not tell if the immune response is rising, declining or static. A single caries score does not describe the current extent of the carious attack, nor the antigenic load of S. mutans that the host is encountering. Some of these problems can be reduced if multiple measurements of the various parameters are taken over a period of time. Longitudinal investigations have been performed in conjunction with caries development in radiation xerostomia patients and in patients who have received symptomatic dental treatment.
長期縱向的研究 之前的研究有斷面的限制。一個單獨的抗體並不能反應免疫反應升高，降低或是持平。一個單一的齲齒數字不能代表目前的齲齒狀況也不能代表宿主目前有S. mutans抗原性。有些問題會因為一段時間用多樣不同的因子衡量後而減少。用長期的檢驗來檢查經過放射線治療後乾口症和接受牙科治療的病人齲齒狀況。
Radiation-Xerostomic Patients. The patients who were studied for bacteriological changes in plaque after radiation therapy (Table 12-5) were also followed immunologically. Serum IgG agglutination titers to S. mutans or lactobacilli pre and post radiation were unrelated to the microbial counts of these organisms in the plaque or to caries activity. This was not the case with salivary IgA levels and antibody titers to S. mutans. Those patients destined to be caries inactive in the post-radiation period had, prior to radiation therapy, significantly higher levels of s-IgA antibody to S. mutans than did those patients destined to develop caries (Table 20-9).
放線後乾口症的病人 研究接受放射線治療後病人的口中牙菌斑細菌變化和免疫反應(Table 12-5) 接受放射線前後，血漿中S. mutans或是lactobacilli 的IgG抗體凝結和牙菌斑中的微生物或齲齒的活性和並不相關。但唾液中IgA含量與S. mutans 抗體卻不一樣。在接受放線治療後無齲齒活性的病人在接受放射線前，唾腺裡S-IgA抗體含量本來就比容易產生齲齒的人來得高。
These data provide strong evidence that, at least in radiation xerostomia patients, salivary IgA antibody rather than serum or salivary IgG antibodies, were involved in caries protection. However, a preeminent role for IgA antibody in this protection cannot be derived from this study, as most of the caries-inactive patients had received intensive fluoride and dietary therapy (Tables 19-6, 19-7). The levels of salivary IgA and agglutinin titers to S. mutans prior to radiation, however, might act as predictors of which patients will develop caries.
這些資料提供了一個強大的證據顯示，除非是接受放線後乾口症的病人，唾腺中的IgA抗體比IgG抗體(不論在血漿或是唾腺中)有更強的抗齲保護力。然而，這研究並不能保證卓越的IgA抗體保護功能，因為此研究中無齲齒活性的病人都有接受密集大量的氟化物和飲食治療。(Table19-6, 19-7)。然而，接受放線治療前的唾液IgA和S. mutans凝集程度可能可以當作此病人是否會有齲齒的預測因子。
Table 20-9
Relationship Between Subsequent Caries Activity and Changes in Salivary Agglutinin Titers to S. mutans and S. sanguis in Radiation Xerostomia Patients
Salivary Salivary agglutinin titer (log2)
Post Radiation
Caries Status IgA IgG Pre-radiation 6 mos 12 mos
Caries Inactive (13)a 5.4 b 8.9b
S. mutansd
S. sanguis 8.0
9.0 10.0
10.5 9.2
9.0
Caries Activec (23)a 3.4 7.1
S. mutans
S. sanguis 6.7
6.8 7.8
7.0 6.7
6.0
a) number of patients
b) percent of total salivary protein
c) caries active patients developed an average of 17.6 carious lesions (range 1-77)
d) titer to S. mutans strain 10449 (serotype c)
values in box significantly different from corresponding value in caries-active patients
Adapted from Brown et al., 1981. J. Dent. Res. 60:10.
Table 20-9
Relationship Between Subsequent Caries Activity and Changes in Salivary Agglutinin Titers to S. mutans and S. sanguis in Radiation Xerostomia Patients
Salivary Salivary agglutinin titer (log2)
Post Radiation
Caries Status IgA IgG Pre-radiation 6 mos 12 mos
Caries Inactive (13)a 5.4 b 8.9b
S. mutansd
S. sanguis 8.0
9.0 10.0
10.5 9.2
9.0
Caries Activec (23)a 3.4 7.1
S. mutans
S. sanguis 6.7
6.8 7.8
7.0 6.7
6.0
a) number of patients
b) percent of total salivary protein
c) caries active patients developed an average of 17.6 carious lesions (range 1-77)
d) titer to S. mutans strain 10449 (serotype c)
values in box significantly different from corresponding value in caries-active patients
Adapted from Brown et al., 1981. J. Dent. Res. 60:10.
Effect of Dental Treatment on Antibody Levels. If serum and salivary antibody levels to S. mutans are a direct reflection of the antigenic load which the host is experiencing in regard to this organism, then treatment which suppresses or eliminates S. mutans might cause a corresponding decrease in antibody titer(s) to S. mutans. This hypothesis was evaluated by reexamining the young adults who had previously been described in terms of antibody levels and caries diagnosis (Table 20-6). During the approximately nine-month interval between examinations, some patients remained caries inactive, some caries-inactive patients developed new lesions, some caries-active patients remained untreated and some received the necessary dental restorations. Challacombe compared the change in antibody titers at the zero and nine-month time periods as a function of the changing clinical status of the patient (Table 20-10).
牙科治療對抗體濃度的影響
如果血清和唾液中的S.mutans抗體是直接反應宿主接觸到的抗原生物體，那治療後就會抑制或是減少S.mutans會造成的抗體反應。這假說用之前表20-6談到的年輕人體中的抗體濃度和蛀牙情形來檢驗。在將近九個月的時間內檢驗，有些病人仍然是齲齒不活躍，有些齲齒不活躍的病人產生了新的病灶，有些齲齒活躍的病人仍未得到牙科治療，有些獲得了需要的牙科治療。Challacombe比較了從一開始到九個月後，病人體內的抗體濃度和臨床狀態的改變。(Table20-10)
Table 20-10
Sequential Change Over a None-month Period in Antibody Titers (Log2) to S. mutans as a Function of Caries Activity or Treatment
Antibody Class
Serum
Young Adults
18-14 years No. of Subjects IgG IgA IgM Saliva IgA
Mean Change in Titerb
No active caries
New caries (1.7)a
Untreated caries (2.2)a
Treated caries 15
10
9
10 0.05
0.6
0.2
-0.9
0.4
0.55
-0.4
-0.6
0.3
0.5
0.6
-0.7
-1.0
0.2
0.7
+1.5
a) mean number of carious lesions
b) serum antibody titers assayed by indirect fluorescent antibody technique. Salivary antibody titers determined by agglutination of whole cells.
values in box reflect significantly different changes in antibody titer. Paired t test.
Adapted from Challacombe, 1980. Archs. Oral Biol. 25:495.
Caries-inactive patients showed no significant changes in the levels of serum antibodies to S. mutans, but exhibited a significant decrease in salivary IgA antibody. In these patients the maintenance of the serum IgG antibody to S. mutans was associated with the caries-inactive state. But in those patients who developed new carious lesions there was a significant rise in serum IgG antibody, which argues that this antibody was not protective (Table 20-10). No significant changes in antibody titers were observed in the untreated patients. However, those caries-active patients who were treated, demonstrated significant reductions in all classes of serum antibodies and a significant increase in salivary IgA antibody (Table 20-10). This last observation was interpreted as indicating that the antigenic load of S. mutans had been decreased by the placement of dental restorations, which in turn, led to decreased synthesis of IgG antibody. Several studies have shown that dental restorative treatment does not significantly reduce the salivary levels of S. mutans (Table 13-1). Thus, the explanation for the decreased titers of S. mutans in the treated group may not be entirely valid.
齲齒活性不強的人在血清濃度裡的S. mutans抗體並沒有顯著的多，但對分泌性IgE抗體有明顯的減少。在這些病人裡，維持血漿中S. mutans的IgG抗體濃度和齲齒不活躍有相關性。然而在產生新病灶的這些病人中，IgG抗體是顯著增加的，這令人質疑是否抗體具有保護性(Table20-10)。在沒有治療的病人裡，抗體濃度沒有顯著性的改變。然而齲齒活躍而接受治療的病人，在血漿中各種抗體都減少了而分泌性的IgA顯著上升(Table20-10)。最後這個觀察被解釋成S. mutans的抗原性會因為放置了牙科復形物而減少，也就是說會降低IgG抗體的合成。有很多實驗都顯示牙科復形治療並不會降低唾液中的S. mutans(Table13-1)。因此，這解釋了在治療組中降低S. mutans的情形並不完全是有效的。
These findings were interpreted as indicating that protection against caries was correlated with high titers of serum IgG to S. mutans and that salivary IgA antibodies to S. mutans were not related to caries resistance. The results do not appear to support this conclusion. In addition, it was suggested that serum IgG antibodies regulate, in a negative feedback fashion, the secretion of salivary antibodies. This would account for the inverse relationship between serum IgG and salivary IgA antibodies to S. mutans. Thus when serum IgG levels decreased, the salivary IgA levels 這個發現可用來解釋血漿中高含量的IgG與唾液中的IgA和防止齲齒並不相關。因為結果並沒有顯示支持他們相關的結論。另外，此結論也指出血漿中IgG抗體用負向回饋調節唾液中抗體的分泌。這解釋了IgG和IgA的相互關係。因此，當血漿中IgG降低，分泌性IgA就會升高。
Summary - Human Studies. These clinical investigations demonstrate the complexity of the interrelationships between serum and salivary antibody titers to S. mutans and caries immunity. There appears to be an immune component in caries protection which was clearly demonstrated by the importance of salivary IgA antibody in the radiation xerostomia and IgA-deficient patients. However, in healthy subjects no protective role for salivary IgA has been shown. In these "normal" subjects there may be a group who mount and maintain a protective serum IgG response to S. mutans and another group who can mount but not sustain such a response. This dichotomy between the relative importance of s-IgA and serum IgG antibodies to S. mutans is sustained by animal experiments which support a role for both classes of immunoglobulins. Thus, vaccines which elicit either an IgA or an IgG response to S. mutans confer some degree of immunity to caries in animal models.
人體實驗的結論 這些臨床的檢驗了顯示血漿和唾液中S. mutans抗體和齲齒免疫反應之間關係的複雜性。這顯示出免疫因子在齲齒保護上的確有功能，這可由唾腺IgA抗體對放線後乾口症病人和缺乏IgA病人身上得到明確的驗證。然而，在健康的個體中，IgA並沒有表現出有保護抗齲的功能。在"正常"的個體哩，可能有一組抗體可以吸附並維持血漿中IgG對抗S. mutans，另一組可以吸附但無法維持這樣的反應。對於S-IgA和IgG抗體這樣的二種理論都可在動物實驗裡得到支持。因此，在一些動物實驗上可證實，疫苗某種程度地能夠引發IgA和IgG對S. mutans的反應。
Mechanisms of Antibody Protection
IgG Classical Mechanisms. If the high titer serum IgG antibody to S. mutans in the caries-free and low-MF individuals indicates a protective antibody response, then we must provide an explanation as to how these antibodies protect. Serum antibodies are readily delivered to sites in vascularized tissue where they combine with antigens to activate the complement system and/or promote surface phagocytosis. This
reaction may take place in the infected pulp and gingival crevice area, but is not likely to occur on the occlusal surfaces of teeth. Immune elements derived from the serum can only reach the organisms responsible for caries if they are liberated into the saliva or, in the case of cells, if they migrate over the tooth surface. Salivary IgG levels are low relative to serum, i.e., l0 to 20 mg/l00 ml saliva vs. l240 mg/l00 ml serum, and complement, if present in the saliva, is so dilute that it cannot be routinely detected. The titer of salivary IgG antibody specific for S. mutans is usually three to five log dilutions lower than the corresponding serum levels. Hence, specific salivary IgG antibody is so dilute that in the absence of concentrating mechanisms, the probability of this antibody encountering a single S. mutans cell is remote. Polymorphonuclear leukocytes (PMNs) enter the mouth primarily via the gingival crevice fluid (gcf). The PMNs remain functional within the gingival crevice and perhaps within that short distance about the gingival margins and interproximal areas over which the gcf flows. Once the PMNs are in saliva, they may degenerate, due to osmotic lysis in the hypotonic saliva.
抗體保護的機制
IgG古典機制 如果無齲齒和低MF的人身上有高濃度的IgG對抗S. mutans反應是代表保護性抗體反應，那麼我們必須提出這些抗體如何保護的解釋。當抗原引起了補體反應或是表面吞噬反應，血漿抗體會被準備製造好藉由血管系統運送過去。這些反應可能發生在被感染的牙髓中或是牙齦溝區域，但不會在牙齒的咬合面出現。血漿中產生的免疫因子只能到達在唾液裡或是細胞裡(當他們移動到牙齒表面時)來對抗造成齲齒的生物體。唾液IgG濃度和血漿濃度有低相關性，例如: 10到20 mg/100ml唾液 vs. 1240 mg/100 ml 血漿，還有如果唾腺中有補體，都被稀釋的很厲害以致於一般時候無法偵測到。唾液中對抗S. mutans 的特殊IgG抗體常常是血漿中三到五次方的稀釋程度。因此唾腺中IgG抗體被稀釋到幾乎不存在在機制裡，這可能因為抗體很少會遇到S. mutans細胞。多形性白血球(PMNs)主要經由牙齦溝液(gcf)進入口腔。PMNs不只在牙齦溝裡有作用且在距牙齦不遠的區或是牙縫間隙區，只要有gcf在的區域，他都有作用。當PMN進到唾液裡，因為滲透壓的關係，他們便開始在低滲透壓的唾液裡分解。
These considerations tend to minimize the protective role which IgG antibodies could play in surfaces which are bathed by saliva. Structures in the flow bed of the gingival crevice fluid however, might be exposed to the necessary concentrations of antibody, PMNs and even complement. Under normal conditions of gingival health the daily volume of the gcf is probably measured in a few mls per tooth surface per day. Whether this is adequate to provide protection against cervical and approximal caries is a matter of speculation. Even so, this protection would not extend to the occlusal surfaces where most caries initiates in humans.
這些降低了IgG抗體在有唾液的牙齒表面上的保護。然而，在有gcf流過的牙齒表面結構上，應會有足夠濃度的抗體，PMN和補體。在牙齦健康的正常情況下，每天gcf的量大約是幾毫升/牙齒表面。我們會懷疑這樣的量是否足夠保護齒頸和齒間不齲齒?即便如此，這樣的保護仍可能可以延伸到人類最容易引發齲齒的咬合面。
Fig. 20-1
Glucosyltransferase inhibition by antibody
Interference with Glucan Synthesis and Binding. If these classic mechanisms for antibody-mediated protection are unlikely to occur in saliva, how then would vaccines protect against caries? A consideration of S. mutans unique ability to form glucans and to adhere to surfaces provides some plausible hypotheses. S. mutans has on its surface at least one glucosyltransferase (GTF) site and a glucan binding site (Fig. 20-1). Suppose that one or both of these sites acts as an antigenic determinant. Antibodies directed toward these sites might inhibit glucan synthesis and/or glucan binding. Interference with synthesis and binding of this retentive polymer could result in an inability of S. mutans to form plaque or to persist in high numbers in plaque. These possibilities have been tested in vitro.
阻礙生醣作用和鍵結 如果抗體保護的古典機制不能在唾液中產生，那疫苗要如何保護防齲?另一個想法是S. mutans有獨特能力能夠合成肝醣而且可以黏附表面的假說。S. mutans表面上至少有一個glucosyltransferase(GTF)位置和一個肝醣建結位置(Fig.20-1)。假設一個或兩個鍵結位置都當作是抗原，抗體直接黏附在這些位置上會抑制肝醣的合成或是鍵結。阻礙合成或是鍵結可以抑制S. mutans產生牙菌斑或是在菌斑中的含量。這些可能性都在體外實驗中進行測試。
Crude GTF isolated from S. mutans was incubated with sucrose in the presence and absence of human sera. The rate of glucan formation was inversely related to the hemagglutinating titer, i.e., the higher the titer, the greater the inhibition of glucan formation. Modifications of this assay using radioactive sucrose have confirmed that specific IgG antibody to S. mutans will inhibit glucan synthesis by S. mutans. Subsequent experiments performed in rodents have shown that vaccines containing purified GTF elicits antibodies which confer a significant degree of protection against a cariogenic challenge with S. mutans. However, the protective antibody(ies) belonged to the IgA class of immunoglobulins (See "Rodent Models" in this chapter).
把S. mutans放在蔗糖中，沒有人類血清下培養分離出天然的GTF。肝醣的合成速度和血凝集程度成負相關，例如凝集多，肝醣合成被抑制的就多。用有放線性的蔗糖可以確認對S. mutans的特殊抗體會抑制S. mutans的肝醣生成。接下來在老鼠身上做的實驗顯示出含有純化的GTF疫苗會引發抗體反應使個體達到某種程度的防齲保護。然而，這些保護性的抗體屬於IgA免疫球蛋白類(見本章中的"老鼠實驗")
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