| PrefaceSecretory immunoglobulin A ( SIgA) not only is a naturally occurred antimicrobial factor in saliva, but also can be induced by specific antigens. It can interfere with attachment of microorganisms on the oral tissure, aggregate bacteria to facilitate their clearance by secretions , and inhibit glucans synthesis so as to lessen the cariogenieity of the mutans streptococcus ( MS). Salivary peroxidase (Spx)can catalyze oxidization of SCN- , all of the product are strong oxidizing a-gents, which can block carbohydrate metabolism after entering bacterial cell, so it also has some inhibition effect on caries. Now there is controversy about the relationship between SIgA ,Spx and caries. One of the reasons is the difficulty in standardization of the measurement method. In this experiment, we used the sensitive, accurate non -competitive avidin - biotion immuno - enzymatic assay ( NAB A) to determine the SIgA concentration , Nb - SCN- method to determine the Spx concentration, at the same time we studied the difference of SIgA, Spx concentration between the caries - susceptible children and caries - resistent ones, as well as their correlation in this two groups. The object of this study is to find some new information about the rela-tionship between antimicrobiol proteins and caries.MethodsTo choose randomly twenty 4 - Syr - old children with caries (dmft ≥5 ) , and twenty caries - free children as control. From the children, 2 ml unstimulated saliva were collected, and their dmft values were recorded. The SIgA concentration were assayed by NABA method in saliva that had been stored at -20℃. Microplates coated with and -human IgA (a chain) were incubated overnight at 37Tl. Then saliva (diluted buffer, standard) , biotinylated anti -human IgA ( a chain) , avidin - peroxidase, enzyme substrate were added successively, at last H2SO4 were added to stop the reaction. Absorbances were read at 405 nm. Calculate SIgA concentration according to the standard curve.The spx concentration were measured by Nb - SCN- method in saliva that had been centrifugated(18,000g, 15min, 4℃)and stored at -20℃. The reaction mixture was made up of 1. 5ml Nbs, 1. 3ml KSCN, 100(0,1 saliva (standard). 200ul mixture were added to the microplates, then 100ul H2O2 were added to make the reaction begin. Absorbances were read at 405 nm for the first minute. Bovine peroxidase was used as standard. The Spx concentration were calculated according to the standard curve.Results1. The SIgA concentration in unstimulated saliva of caries - re-sistent children was 75. 73 ±2. 1μxg/ml, in saliva of caries - sus-ceptible children is 52.44± 13.23u,g/ml. The former was significantly higher than the latter ( P < 0.01) .2. The Spx concentration in unstimulated saliva of caries - resis-tent children was 7.007 ± 3.228μg/ml, in saliva of caries - susceptible children was 5. 865± 2. 297μLg/ml. There was no significant difference between them ( P >0.05).3. SIgA and Spx correlated significantly in caries - resistant children, correlation coefficient was 0. 72(P <0.01) , but there was no significant correlation for them in caries - susceptible children, correlation coefficient was 0. 38 ( P >0.05 ).DiscussionEarly in 1960s, Keyes had proved caries is a kind of infectious disease. MS is the major cariogenic bacteria. Both SIgA and Spx are important antimicrobial proteins in saliva, which can disturb the action of bacteria through several mechanisms. But studies aimed at correlating SIgA and Spx with resistance or susceptibility to dental caries have given variable and conflicting results over the years for several reasons. One of the most important reasons is the difficulty of the standardization of the measurement method. The usually used single immunodiffusion is too crude; radioimmuno - assay has the shortcoming of applying radioisotope. Enzyme - linked immunosorbent assay (ELISA)is also less sensitive than NAB A. Over the past few years, NAB A had been applied to determine SIgA concentration overseas. Th...
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