Histopathologic analysis of experimental autoimmune uveitis attenuated by intracameral injection of S-antigen

Pretreatment of rats and mice with intracameral injections of soluble protein antigens induces Anterior Chamber Associated Immune Deviation, an unusual spectrum of immune reactivities that is dominated by suppression of the efferent limb of the immune response. Pretreatment of Lewis rats with an intracameral injection of S antigen (S Ag) mitigates against the development of clinically detectable experimental autoimmune uveitis if these rats are subsequently injected with a uveitogenic dose of S Ag. In this report, we describe a series of histopathologic studies designed to determine the extent and severity of changes that occur in the eyes of rats pretreated with intracameral S Ag. The results indicate that pretreatment with intracameral injection of S Ag alone or mixed with Complete Freund's Adjuvant significantly inhibited the development of severe uveoretinitis. In the eyes of the majority of rats, the histologic appearance was completely normal, without any evidence of pathologic changes. A minority of rats displayed clinical evidence of uveitis, and their eyes contained histopathologic changes. These changes suggested that a mild form of uveoretinitis had taken place. It is proposed that S Ag-specific suppression of delayed hypersensitivity is induced by the anterior chamber injection of this antigen, and that this suppressor activity accounts for the reduced severity of disease in the eyes of treated rats. The potential physiologic significance of suppression in response to exposure to unique ocular antigens is discussed.