Naturally occurring secretory immunoglobulin A antibodies to Streptococcus mutans in human colostrum and saliva

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Abstract
Human colostrum, parotid saliva and serum were assayed for the presence of naturally occurring antibodies to 5 serotypes of S. mutans. Appreciable levels of agglutinins to strains AHT, BHT, 10449, 6715 and LM-7 (groups a .fwdarw. e, respectively) were detected in normal colostrum and saliva; relatively low levels were found in serum. No agglutinins could be detected in the colostrum or saliva of immunodeficient patients. Molecular sieve chromatography of the colostrum on Sephadex G-200 revealed agglutinin activity in the secretory immunoglobulin A (s-IgA)-rich fraction only. Titration of purified colostral s-IgA confirmed the IgA nature of this agglutinating activity. Indirect immunofluorescence tests with anti-s-IgA, -IgG, and -IgM revealed S. mutans specificity only in the s-IgA class. The presence of s-IgA antibodies to indigenous oral microorganisms in colostrum and saliva, suggests that antigenic stimulation occurs at a site remote from the oral mucosa.