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.

A common mucosal immune system. Antibody expression in secretions following gastrointestinal stimulation.

Isoelectric focusing was used to probe the expression of IgA anti-DNP antibodies in secretions of rats receiving gastrointestinal immunization. The identity of the IgA antibody spectrotypes suggest that cells with identical clonotype potential seed various secretory surfaces following gastrointestinal stimulation. The data are discussed in terms of a common mucosal immune system linked by migrating populations of IgA precursor cells.

The induction and expression of IgA anti-DNP antibodies in rat bile and secretions.

Pregnant rats were immunized with dinitrophenylated type III-pneumococcal vaccine by the intravenous, gastric, or intramammary routes. Anti-DNP antibody responses in the IgA, IgG and IgM isotypes were measured in serum, secretions and bile. Gastric intubation was most effective at eliciting IgA antibody responses in bile and secretions, whereas the other routes were more effective at inducing IgG responses in serum and bile. IgM antibody responses were infrequent and were found in fluids most closely associated with the immunization route. Isoelectric focusing studies of IgA antibodies appearing in secretions and bile revealed that the gastric route consistently elicited antibody spectrotypes with shared components. Intravenous and intramammary immunization resulted in IgA spectrotypes possessing less homology, suggesting that these protocols lead to independent antibody responses triggered in spleen, draining lymph nodes, or secretory sites. After gastric stimulation, the appearance of IgA antibodies with identical spectral components in secretions and bile favours the concept that IgA precursor cells with identical clonotype potential migrate from the gastrointestinal area to secretory sites. Antibody expression in bile appears to result from the selective transfer of IgA populations gaining access to serum after synthesis at a secretory site.

Molecular diversity of secretory IgA anti-DNP antibodies elicited in rat bile.

Dinitrophenylated-type III pneumococcus has been used to induce biliary IgA anti-DNP antibody responses in rats. A solid phase radioimmunoassay was employed to quantitate the biliary IgA anti-DNP antibodies after subcutaneous, i.v., or intragastric immunization. All routes were shown to effectively elicit biliary IgA antibody responses. The microscale sucrose isoelectric focusing technique was employed to assess molecular diversity of the secretory IgA anti-DNP antibodies in bile. Subcutaneous and intragastric immunization resulted in complex antibody spectrotypes whereas i.v. immunization yielded restricted antibody spectrotypes, demonstrating that the route of immunization influenced the molecular diversity of the biliary secretory IgA antibodies. These findings are discussed in terms of mechanisms governing the induction of secretory antibodies.