| Abstract: | The effects of feeding the dietary protein antigen, ovalbumin (OVA), on OVA-specific IgG and IgA immune responses involving Peyer's patches (PP) and mesenteric lymph nodes (MLN) were examined. Mice were administered soluble OVA by gastric intubation. One to 3 days later, PP, MLN, or spleen cells from these donor mice were adoptively transferred into normal syngeneic recipients. After two subsequent immunizations, spleens from the recipient mice were assayed for IgA and IgG anti-OVA plaque-forming cell (PFC) responses. None of the tissues from normal (unfed) mice had the inherent ability to alter recipients' IgG or IgA PFC responses. Within 1 day of OVA feeding, however, cells were generated in the PP that could augment recipients' IgA anti-OVA PFC responses and suppress IgG PFC responses. Three days after OVA feeding, these cells were present in MLN as well, and whereas the IgG suppressor cell also appeared to migrate to spleen, the IgA helper cell did not. The cells mediating antigen-specific IgG suppression and IgA help were both T cells but could be distinguished by surface phenotype. We therefore conclude that protein feeding induces differential, isotype-specific immunoregulation in gut-associated lymphoid tissues, part of which is mediated by an antigen-specific IgA helper T cell. |
