Parameters influencing the expression of IgA antibodies in tears

Rats were immunized repeatedly with dinitrophenylated type III pneumococcal vaccine by the intravenous (IV), subcutaneous (SC), gastrointestinal (GI), or ocular/topical (OT) routes at biweekly intervals. IgA anti-DNP antibodies were measured in serum, tears, saliva, bronchial, and intestinal washings, obtained 7 days after the third and sixth immunizations, using a solid phase radioimmunoassay. The GI route most effective at eliciting and maintaining IgA antibody responses in tears. The OT group displayed markedly diminished IgA response frequencies and antibody levels in tears following prolonged immunization. These data show that repeated central mucosal (gastrointestinal associated lymphoid tissue) stimulation maintains a local IgA response in tears, while continued topical antigen stimulation does not. Isoelectric focusing was used to probe the spectral complexity of the IgA antibodies of individual animals undergoing GI and OT immunization. The reduction of spectral complexity and the decreased responses following OT immunization appear to reflect a diminution of IgA antibody producing cells in the lacrimal gland. The concomitant changes in spectral components and maintenance of responsiveness of the GI group suggests that central mucosal site stimulation provides the lacrimal compartment with a continuous but variable population of IgA antibody producing cells.