Salivary IgA in minor-gland saliva of children, adolescents, and young adults.

According to previous studies, minor glands produce about 35% of the total salivary immunoglobulin A (salivary IgA). The age-dependent increase in whole-saliva salivary IgA concentrations has been studied extensively, but we found no published reports comparing the minor-gland saliva concentrations of salivary IgA in children, adolescents, and adults. In this study we measured the concentration of salivary IgA in saliva from the labial and the buccal minor glands of children, adolescents, and adults. Three age groups donated saliva for analysis: 3-yr-old children, 14-yr-old adolescents, and 20- to 25-yr-old adults. Minor-gland saliva was collected on filter paper and unstimulated whole saliva was collected by draining into a tube, and the salivary IgA concentration was determined by ELISA. The salivary IgA concentration in labial saliva was significantly lower among 3-yr-old children (0.037 mg 100 ml(-1), SD = 0.035) than among 14-yr-old adolescents (0.126 mg 100 ml(-1), SD = 0.128) and adults (0.128 mg 100 ml(-1), SD = 0.13). The 3-yr-old children also had significantly lower whole-saliva salivary IgA values compared with the other age groups (0.09 mg 100 ml(-1), SD = 0.091; 0.179 mg 100 ml(-1), SD = 0.149; and 0.170 mg 100 ml(-1), SD = 0.099, respectively). This increase in salivary IgA concentrations with age might reflect a developing immune response in the growing child.

HLA, salivary IgA and mutans streptococci--is there a relation?

The aim of the present studies was to investigate a possible relationship between the human leukocyte antigen (HLA) complex, colonization of mutans streptococci and salivary immunoglobulin A (IgA) antibodies against mutans streptococcal antigens. In the first study a strong inverse relationship between HLA-DR4 and levels of mutans streptococci was observed for a group of renal transplant patients (I). In a group with healthy blood-donors a similar trend was observed (I). This tendency was also seen for a selected population investigated in the second study (II). Since the HLA molecules regulate the production of antibodies in saliva, the salivary IgA activity to three oral streptococci in a population of HLA-DR4-positive and DR4-negative subjects was investigated in the following study (III). It was found that the HLA-DR4-positive subjects, especially the DRB1*0401 and DRB1*0404 subgroups, showed a weaker IgA activity, in particular to Streptococcus mutans, as compared to the HLA-DR4-negative. However, immune response patterns revealed by Western blotting are often complex and for further studies with larger study populations it was crucial to unravel the nature of the detected antigens. In the fourth study (IV), untreated saliva, as well as saliva, in which cell-surface reactive IgA had been absorbed with whole bacteria cells, were analysed in Western blot against different oral streptococci. The high molecular bands, that were absent after absorption, likely represented cell-surface antigens and were thus of interest as they might be involved in adhesion mechanisms and available for blocking in vivo. In the next study (V), the salivary IgA activity to cell-surface antigens of three oral streptococci in relation to different HLA-DRB1*4 alleles was studied in a larger population. The immunoblots were analysed in a computer program and intensity graphs revealed that the DRB1*0401 and *0404 subgroups, compared to other DRB1*04 types, showed fewer as well as less intense immunoblot bands to antigens from S. mutans, S. sobrinus and streptococcal antigen (SA) I/II, but not S. parasanguis. The main conclusion from this thesis is that the HLA profile of the individual seems to influence the salivary IgA response to mutans streptococcal antigens and might thus also affect the conditions for the bacteria in the oral cavity.