Mechanisms of Peripheral Tolerance following Intracameral Inoculation Are Independent of IL-13 or STAT6

The peripheral tolerance that is elicited by the anterior chamber-associated immune deviation (ACAID) protocol is characterized by impairment of Th1 responses such as delayed-type hypersensitivity. It has been proposed that suppression of Th1 responses is mediated by a deviation toward Th2 responses. Because NKT cells have a prominent role in ACAID and NKT cell-derived IL-13 is required in a tumor model of tolerance, we postulated that NKT cell-derived Th2 cytokines might have a role in ACAID. However, contrary to the tumor model, in this study we show that NKT cells from IL-13-deficient mice or IL-4/IL-13 double deficient mice were able to reconstitute the capability of J alpha18-deficient mice (lacking invariant NKT) to develop peripheral tolerance postintracameral inoculation of Ag. Also, we were able to induce peripheral tolerance directly in IL-13-deficient, IL-4/IL-13-double deficient, and STAT6-deficient mice by inoculation of Ag into their eye. We conclude that neither IL-4 nor IL-13 cytokines are required for the generation of efferent CD8+ T regulatory cells during eye-induced peripheral tolerance. We propose that Ags inoculated into the anterior chamber of the eye induce the immunoresponse to deviate from producing immune T effector cells to producing efferent T regulatory cells, rather than deviating from Th1- to Th2-type effector cells.