Inhibition of lymphocyte proliferation by a monoclonal antibody (RFT2) against CD7

The effect of the monoclonal antibody RFT2, directed against CD7, on T cell proliferation in unseparated peripheral blood mononuclear cell populations induced by various stimulants was investigated. The addition of RFT2 to cell cultures inhibited the T cell proliferation induced by tuberculin PPD and OKT3 but not by phytohaemagglutinin, concanavalin A or phorbol myristic acid; RFT2 had to be present during the first 24 h of culture in order to elicit inhibition; inhibition of proliferation was not due to down regulation of interleukin-2 receptor on the surface of T cells; and suppressive effects could be transferred by mononuclear cells pre-treated with RFT2. These results are of particular relevance in view of the known in vivo suppressive effect of RFT2 in humans.