Regulation of CTL recognition by receptors for HLA-DR molecules

NK cells and some T cells have receptors for MHC class I molecules that negatively regulate the recognition of these cells. In the present study, we show alpha beta CTL clones carrying the receptors for HLA-DR molecules that inhibit this cytotoxicity. The cytotoxicity of two CTL clones possessing NK activity was inhibited by the surface expression of HLA-DR and HLA class I molecules on the target cells. The inhibitory effect of DR molecules on the cytotoxicity of the CTL clones was confirmed by using T2 transfectants expressing HLA-DR3. These results suggest that receptors for both HLA-DR and HLA class I molecules negatively regulate the recognition of T cells.