Abstract
An important factor in the establishment of ocular immune privilege is the dynamic down regulation of T helper 1 (Th1) immune responses that occurs in response to antigens delivered intraocularly; a phenomenon that has been termed anterior chamber-associated immune deviation (ACAID). ACAID is characterized by the generation of splenic regulatory cells that inhibit the expression of delayed-type hypersensitivity. Previous studies have shown that antigens introduced into the anterior chamber of the eye induce the generation of a CD4+ T-cell population that suppress the induction of Th1 immune responses and the appearance of a second population of CD8+ T regulatory cells that suppresses the expression of Th1 inflammatory responses (= efferent suppressor cells). Experiments described here characterized the function of the CD4+ ACAID suppressor cell population and its effect on the generation of CD8+ efferent suppressor cells that inhibit the expression of DTH in situ. Both in vivo and in vitro experiments demonstrated that CD4+ T cells are required for the generation of CD8+ efferent suppressor cells. CD4+ T cells do not require cell contact with CD8+ T cells; instead they produce soluble IL-10 that is sufficient for the generation of ACAID suppressor cells. Finally, the CD4+ afferent T suppressor cells are not natural killer T cells, but do express the CD25 cell surface marker.