HUMAN SALIVARY IMMUNOGLOBULIN A - SOME IMMUNOLOGICAL AND PHYSICOCHEMICAL CHARACTERISTICS

Human ascitic and salivary immunoglobulin A (IgA) were isolated and compared for their immunological and physicochemical properties. Salivary IgA, with a sedimentation coefficient of 11.0 S, had a molecular weight of 390 000; it consisted of two molecules of ascitic type IgA (mol. wt. 170 000) bound to one molecule of secretory piece (mol. wt. 50 000). Reduction and alkylation (pH 8.2) split the salivary IgA into fragments corresponding to ascitic IgA molecules and a secretory piece. Reduction and alkylation (pH 8.2) split a portion of ascitic IgA into fragments of a molecular weight of about 60 000 of which some corresponded to heavy chains and others to dimers of L chains. Treatment with urea or guanidine dissociated the salivary IgA into two fragments of about the same molecular weight; the first corresponded to ascitic type IgA, the second to molecules formed by two α-chains bound to the secretory piece. The secretory piece, isolated by reduction and alkylation, had an electrophoretic mobility faster than that of salivary IgA. It possessed no antigenic determinants common to L chains but only determinants specific for secretions. © 1969.