藤橋 浩太郎

Our studies have given direct evidence that CD3+, CD4-, CD8+ T cells in the IELs can be separated into at least two subsets that produce IFN-gamma and/or IL-5 and may exhibit Th1- and Th2-type functions in the epithelium and in the underlying lamina propria region. Further, it was also shown that TCR1+ T cells in IELs are capable of producing IFN-gamma and/or IL-5. In addition to production of these cytokines, IELs derived from mice orally primed with TD antigen contain a subset of T cells which posses antigen-specific immunoregulatory function. CD3+; CD4-, CD8+ T cells isolated from IEL of TD antigen-primed mice abrogated systemic unresponsiveness to secondary-type responses including those of the IgA isotype upon adoptive transfer to mice with OT. Our studies further suggested that these CD3+, CD4-, CD8+ IELs use the gamma-delta-form of TCR (TCR1) for their immunoregulatory function.

In summary, we have shown that human appendix and murine PP B cells, freshly isolated from normal tissue, respond to IL-6 with significant increases in IgA SFC. Further, sIgA+ B cells from appendix express more IL-6R than is seen with B cells isolated from PBMC and spleen. When IgA subclass responses were measured, rhIL-6 induced both IgA1 and IgA2 SFC responses; however, 60-70 % of the total response was represented by the IgA2 subclass. Our studies suggest that the human appendix as well as murine PP are enriched sources for sIgA+ B cells which are responsive to cytokines such as IL-6 for induction of IgA plasma cell responses.