Heat-shock protein 60 derived from Yersinia enterocolitica (Yersinia HSP 60) and bovine retinal HSP (Retina HSP 60) were previously identified by immunological cross-reaction and a high degree of common antigenicity, and a specific antibody against both proteins was detected in the sera of uveitis patients. We report here an attempt to isolate and purify Retina HSP 60 and Yersinia HSP 60. Both Retina HSP 60 and Yersinia HSP 60 showed an enriched content of glycine of approximately 60 to 80%. Lewis rats were inculated with 50 or 100 micrograms of purified Retina or Yersinia HSP 60 emulsified in complete Freund's adjuvant. In 50 to 60% of those inoculated with Retina HSP 60, uveoretinitis was observed about 13 days after inoculation, with massive infiltration of lymphocytes and polymorphonuclear neutrophils in the iris, ciliary body, and retinal tissue. Rats inoculated with Yersinia HSP 60 did not develop ocular inflammation. Lymphocyte proliferation assay was performed to investigate cellular immunoresponses in the rats that developed ocular inflammation after immunization with Retina HSP 60. The results showed significantly higher response to the Retina and Yersinia HSP 60 than to either S-antigen or interphotoreceptor retinoid-binding protein (IRBP), which are known to induce ocular inflammation. Cross-reaction between Retina and Yersinia HSP 60 is suggested. This study suggests that the HSP 60 molecules may be involved in the pathogenesis of intraocular inflammation.