HLA-DR4 and salivary immunoglobulin A reactions to oral streptococci

The aim of this study was to describe and compare salivary immunoglobulin A (IgA) antibody reactions to extracts of strains of three oral streptococci in human leukocyte antigen (HLA)-DR4-positive and -DR4-negative subjects. Whole paraffin-stimulated saliva samples were collected from 27 apparently healthy subjects. Previous HLA typing showed that 20 subjects were DR4 posi tive and 7 were DR4 negative. HLA-DRB1*04 subtyping was performed among the DR4-positive subjects. Whole-cell antigen extracts from Streptococcus muta ns (KPSK 2), Streptococcus sobrinus (OMZ 65) and Streptococcus parasanguis (Nt 62) were separated in SDS-PACE. The antigens were immunoblotted with di luted saliva (Western blot), scanned and analyzed in a computer system. All immunoblot bands were recorded in DR4-positive and DR4-negative saliva poo ls, and bands with an optical density greater than or equal to0.1 were sele cted for analysis in individual salivas. The DR4-negative subjects in gener al had more immunoblot bands and more distinct bands than did the DR4-posit ive subjects. A higher concentration of total IgA in saliva was correlated with more bands, especially to antigens separated from S. mutans. When the number of bands was calculated per IgA unit, significant differences were o bserved between DR4-positive and DR4-negative salivas. This was particularl y seen for S. mutans and S. parasanguis. As the number of bands was analyze d in relation to DR4 subgroups, DRB1*04, there was a lower salivary IgA act ivity to S. mutans in the DRB1*0401 and *0404. The variable level of correl ation previously demonstrated for S. mutans colonisation and serologically defined DR4 positive subjects might be explained by the heterogeneity in th is group, and the relation should be sought on a subgroup level.