Effect of denaturization on the immunogenicity and uveitogenicity of retinal S-antigen

Previous studies have shown that alteration of pH or temperature of retina extract can affect its complement fixing reactivity with anti-S-antigen serum. To examine the effect of pH or heat on the immunogenicity and uveitogenicity of purified bovine S-antigen, guinea-pigs were injected with pH- or heat-treated S-antigen and evaluated for clinical and histopathological signs of uveoretinitis, histopathology of pineal gland, serum and intraocular S-antigen antibody reactivity, and S-antigen skin test reactivity. Guinea-pigs that received pH 7 or pH 10 treated S-antigen responded as did those that received untreated S-antigen. Guinea-pigs injected with pH 4 or heat-treated S-antigen exhibited lower incidence, later onset and less severe uveitis than those that received untreated S-antigen. Systemic responses of skin test reactivity to S-antigen were not different from those of the control group; pineal gland involvement and serum anti-S antibody reactivity were slightly reduced. Skin test responses of animals receiving treated antigen were less to the treated (injected) antigen than to untreated S-antigen. In addition, antibody responses of guinea-pigs receiving pH 4 or heat-treated antigen were less to the treated (injected) antigen than to untreated S-antigen. These results suggest that the sites on the S-antigen molecule responsible for various aspects of pathogenicity and immunogenicity do not have the same sensitivity to physical/chemical treatment and may reside on different parts of the molecule. Furthermore, the reactive sites especially for antibody and skin test reactivity, may be continuous sites.