Humoral immunity to heterotopic corneal allografts in the rat

Despite indications that humoral immune responses may be involved in corneal allograft rejection, few definitive reports of such responses exist, and the antigens responsible for evoking and targeting these responses remain unknown. We report the development of donor-specific humoral immunity in PVG (RT1(c)) rats given fully allogeneic ACI (RT1(a)) corneal grafts heterotopically. PVG anti-ACI cornea serum lysed ACI, but not PVG, target cells in complement-dependent cytotoxic assays. Target cells from PVG.1A or PVG.R1 congenic rats, which respectively share the entire rat major histocompatibility complex (MHC) region (i.e., RT1) or only class I MHc antigens (RT1.A region) with ACI (on PVG backgrounds) were also lysed by this serum. Lysis of PVG.1A targets was significantly more extensive than lysis of PVG.R1 cells, indicating that both RT1.A and non-RT1.A antigens act as targets for cell lysis. Levels of PVG.1A and ACI target lysis were equivalent, suggesting that minor transplantation antigens were not significantly involved in this humoral response.