ROLE OF CD4+ T-CELLS IN THE REGULATION OF IMMUNOREACTION IN THE MUCOSA

IgA isotype responses are regulated by at least two compartments including those of CD4+ Th2 type cells and cytokines produced by these cells. Interactions of CD4+ Th2 type cells and antigen-presenting cells (e.g., B cells and M0) via TCR and Ag-MHC II leads to activation of T helper cells. This would lead to the secretion of interleukins, such as IL-5 and IL-6 which are important cytokines for the terminal differentiation of B cells into Ig secreting plasma cells. Further, expression of Fc-alpha-R(II) on CD4+ Th2 cells could be important for the selection of sIgA+ B cells which would allow specific interactions of Th2 cells and sIgA+ B cells via the expressed Fc-alpha-R. This would allow selective transfer of IL-5 and IL-6 to sIgA+ B cells from CD4+ Th2 cells for IgA responses.