Carrier-specific recognition for induction of secretory IgA anamnestic antibody responses.

This study examined antigen-carrier specificity for the induction of secretory IgA antibodies in the saliva of rats. Conjugate antigens used as probes to examined the formation of SIgA antibodies included: DNP-BGG, DNP-OVA and DNP-Streptococcus mutans, as well as the unconjugated carriers BGG and OVA. The results showed that local immunization of rats with homologous hapten-carrier conjugates (i.e. DNP-BGG + DNP-BGG) resulted in secondary responses of salivary IgA and serum IgG and IgA antibodies to the hapten DNP. In contrast, heterologous conjugate (i.e. DNP-BGG + DNP-OVA) administration was unable to provide priming for anamnestic secretory or systemic responses. Priming of rats with unconjugated carrier was found to enhance the response to a local immunization with hapten-carrier antigen only in an homologous system. Also, significant carrier priming was most pronounced with serum IgG and IgA. While salivary IgA was increased somewhat following priming with unconjugated carrier, this was less than following two immunizations with the homologous hapten-carrier conjugate. These findings demonstrate carrier-specific reactions in the elicitation of secretory IgA antibodies and further support evidence of the importance of T-cell co-operation in the induction of secretory immune responses.