Human retinal S-antigen. Isolation, purification, and characterization.

S-antigen, a highly pathogenic agent for the inducation of experimental autoimmune uveitis ( EAU ), was obtained in a pure state from human retina by conventional salt fractionation, molecular sieve and ion exchange chromatography. The physical and chemical properties of the purified protein including the molecular weight, isoelectric point and amino acid composition were determined. The physical properties of the purified human retinal S-antigen were similar, but not identical, to those previously reported for bovine retinal S-antigen (J Immunol 119:1949, 1977). Following the injection of 50 micrograms of human retinal S-antigen into the footpads of guinea pigs, EAU was documented both clinically and histopathologically. The relationship between S-antigen, uveitis, and the pineal gland is discussed.