The induction and characterization of secretory IgA antibodies.

In addition to humoral immunity, which is characterized by the presence of circulating antibody, a second distinct type of immunity involves the localized production of secretory antibodies (reviews 1,2,3). Numerous investigators, employing different antigens in a wide variety of animal systems, have been able to stimulate localized antibody production (4–13). The characteristic structural features of secretory IgA (review 3), which allows it to be differentiated from its serum counterpart, make IgA the ideal immunoglobulin class to be used in studies on the inductive process. Of particular relevance to our current studies was the demonstration that local immunization, by the intramammary route, with either dinitrophenylated bovine gamma globulin (6) or group A streptococci (8) could induce specific colostral IgA antibodies. Other evidence strongly suggested that gut associated lymphoid tissue was not only involved in the production of intestinal IgA antibodies (5, 9, 11, 13), but also might play a role in IgA production at remote sites (7, 9, 10, 12) including secretory sites (10, 12, 14).