The serum antibodies specific to either interphotoreceptor retinoid-binding protein (IRBP) or retinal S-antigen were longitudinally determined in Lewis rats immunized with 50 x 10(-6)g of IRBP emulsified with complete Freund's adjuvant. To our knowledge, it is the first time to purify IRBP and to address the experiment with IRBP in China. It was shown that the antibody specific to IRBP appeared on the 7th day, followed by a gradual increase, and reached its peak on the 26th day after immunization. No antibody specific to S-antigen was found. The relation between anti-IRBP antibody and experimental autoimmune uveoretinitis (EAU) which occurred in the increasing phase of the antibody suggests that the humoral immunity may be implicated in the pathogenesis of EAU.