The role of LFA-1 in class II restricted, antigen-specific T-cell responses.

We have studied the role of the murine lymphocyte function associated antigen-1 (LFA-1) in the major histocompatibility complex (MHC)-restricted responses of a panel of T-cell hybridomas to protein antigens. Monoclonal antibodies to LFA-1 showed a differential blocking effect in these responses that correlated with the overall "sensitivity" of a given hybrid to antigen and MHC as defined by other criteria already reported. This result differs completely from similar experiments in the CTL system where all clones regardless of their overall "avidity" for target cells are very sensitive to the blocking effects of anti-LFA-1. Further, we show that no blocking effects are observed in the response of our hybridomas when Class I or Class II transfected fibroblasts or cultured 3T3 fibroblasts are used as synthetic antigen presenting cells and the result is unaltered by preincubation of such cells with interferon-gamma (IFN-gamma).