Meth A cell whole membranes suppress CTL lytic ability while B/c-N membranes do not. Whole membranes were prepared as described in Materials and Methods. A cold target inhibition assay was prepared with H-2^d anti-H-2^b CTLs and EL-4 ⁵¹Cr-labeled target cells. The diamond indicates CTL killing in the absence of cold target (effector to target ratio 10).