Abstract The in vitro effects of cyclosporin A, prednisolone, and anti-CD4 monoclonal antibody WW.T4 on myelin basic protein-specific human CD4 + cytolytic T lymphocyte clones were studied. Functional assays of antigen-specific proliferation, induction of specific lysis, cytolysis itself, and interferon-γ production were done. Prednisolone decreased secretion of interferon-γ by the clones and blocked specific proliferation; the latter could, however, be overcome by the addition of exogenous interleukin 2. It did not influence cytolytic properties. In contrast, cyclosporin A and WW.T4 blocked the four antigen-specific functions of the autoimmune myelin basic protein-specific T cells clones measured.