Immunochemical evaluation of S-antigen of rabbit pineal gland

Purified S-antigen of photoreceptor cells induces experimental autoimmune uveoretinitis (EAU) and experimental autoimmune pinealitis (EAP) in laboratory animals. However, in rabbits, S-antigen induces only EAU without EAP. To evaluate this difference, the authors studied immunochemical reactivity of rabbit pineal gland with a panel of anti-S-antigen monoclonal antibodies (MAb). Rabbit pineal gland reacted with the MAbs by ELISA and immunoblot but not by immunohistochemistry. In contrast, rabbit retina like guinea pig retina, guinea pig pineal gland and bovine retina reacted with these MAbs by immunohistochemistry as well as by ELISA and immunoblot. Also, S-antigen purified from rabbit retina reacted as did bovine and guinea pig S-antigen. Therefore, S-antigen in situ in rabbit pineal gland is different from S-antigen of rabbit retina and different from S-antigen of pineal gland and retina of other species. Just as the MAbs did not react with S-antigen in rabbit pineal gland, it is possible that S-antigen activated lymphocytes may not recognize S-antigen in rabbit pineal gland and thereby not induce EAP.