Studies in animals and in patients are being carried out to determine factors influencing ocular immune responses. In an animal model, rats are immunized with S-retinal antigen to produce experimental autoimmune uveitis. Animals in one group received anti-Ia antibody intraperitoneally and developed the onset of uveitis significantly later and to a lesser extent than controls. Histopathologically, the anti-Ia treated animals had much less inflammation than did controls. A human eye with pars planitis was also studied immunohistologically. In the pars plana region there was an elevated helper to suppressor T-cell ratio. In addition, the snowbank area showed staining for glial fibrillary acid protein Muller cells, type IV collagen and laminin. There was staining for HLA-DR throughout the globe. The results of these studies shed light on how surface antigens effect and are transmitted by ocular immune responses.