Degradation of human secretory immunoglobulin A by protease isolated from the anaerobic periodontopathogenic bacterium, Bacteroides gingivalis.

This bacterium is implicated in periodontal diseases of human adult type. Secretory immunoglobulin A (IgA) purified from human colostrum (HC-IgA) was incubated with Bacteroides gingivalis cells or protease isolated from the culture supernatant of B. gingivalis; the digestion of IgA was determined by immunoelectrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. B. gingivalis cells almost completely degraded HC-IgA; protease isolated from the culture supernatant cleaved both HC-IgA and secretory IgA in human parotid saliva. Thus by degradation of IgA, the protease may mediate in part the periodontopathogenic role of B. gingivalis by decreasing the oral defence mechanism.