Role of antigen in migration patterns of T cell subsets arising from gut-associated lymphoid tissue.

Studies of the migration of antigen-specific regulatory T cell subsets responding to gut immunization were undertaken to clarify their migratory potential and the role of antigen in their localization. In initial experiments, lymphocytes collected from the thoracic duct of rats after immunization of Peyer's patches (PP) with keyhole limpet hemocyanin (KLH), were enriched for T helper (Th) cells and labelled with the fluorochrome H33342. In other experiments, a higher frequency of antigen-specific T cells was achieved by short-term culture of the enriched Th cells in the presence of KLH and the blast cells labelled with 3H-thymidine. The distribution of both populations was determined after injection into immunized and unimmunized syngeneic recipients. Whereas the uncultured population (predominantly small Th cells) localized almost exclusively in follicular lymphoid tissues, the cells expanded by secondary culture (predominantly Th blasts) appeared in the gut lamina propria (LP) initially, then in PP and mesenteric lymph nodes. The Th blasts in the LP were almost always seen in close proximity to the gut epithelium. However, the migration of neither population appeared to be influenced significantly by antigen, in contrast to previous findings with regard to IgA-committed B cells. The initial subepithelial location of Th blasts in the gut LP and their subsequent appearance in PP may provide a mechanism by which antigen presented by epithelial cells could influence B cell differentiation in PP through modulation of signals expressed by these T cells.