Immunoglobulin A subclass distribution of naturally occurring salivary antibodies to microbial antigens.

The distribution of immunoglobulin A1 (IgA1) and IgA2 antibodies to various microbial antigens was determined in human parotid saliva by using monoclonal antibodies to the IgA subclasses in a solid-phase radioimmunoassay. In 12 subjects examined, antibodies to Streptococcus mutans glucosyl transferase, protein antigen I/II, and cell wall carbohydrate, as well as dextrans B1355 fraction S and B512 and phosphorylcholine, occurred predominantly in the IgA1 subclass. In contrast, antibodies to lipoteichoic acid from Streptococcus pyogenes and whole lipopolysaccharides from Bacteroides gingivalis, Bacteroides fragilis, and Escherichia coli were predominantly of the IgA2 subclass. The data indicate that in most individuals naturally occurring antibodies to a given antigen are predominantly associated with one of the two subclasses of IgA.