The isolation and characterisation of T cell clones or lines specific to retinal antigens are valuable tools to clarify the underlying mechanisms of autoimmunity to retinal antigens as a contributing factor in ocular inflammation. Patients with Behçet's disease have been reported to be sensitised to S-antigen (S-Ag). In the present study, four T cell clones established from the peripheral blood of a patient with Behçet's disease were analysed. A CD4+ T cell clone (clone 2) and a CD8+ T cell clone (clone 10) proliferated specifically to bovine S-Ag. Although these S-Ag specific T cell clones proliferated vigorously to the intact antigen, their responses to S-Ag derived synthetic peptides M and G were weak, suggesting that the sites of human T cell recognition of S-Ag may be different from those established in the experimental model. The proliferative responses of both clones (2 and 10) were inhibited by anti-HLA-DR monoclonal antibody but not by anti-HLA-class 1 monoclonal antibody. The other two clones studied, clones 6 and 30, were CD3+, CD4-, CD8-, and they did not proliferate specifically to S-Ag. Clone 6 expressed gamma delta T cell receptors (TCR) and showed non-specific cytotoxic activity toward K562 and Daudi cell lines. Clone 30 expressed alpha beta TCR, and was devoid of cytotoxic activity. Human T cell lines and clones specific to retinal antigens will provide the framework necessary to examine the events that lead to ocular inflammation.