Generation of cytotoxic T cells in the rat mixed lymphocyte reaction is blocked by monoclonal antibody MRC OX-8.

MRC OX-8 is a mouse anti-rat monoclonal antibody which binds to thymocytes, cytotoxic T cells, suppressor cells and the majority of natural killer (NK) cells. Addition of this antibody at the beginning of a mixed lymphocyte reaction (MLR) inhibits the generation of cytotoxic T cells, assayed after 5 days. However, MRC OX-8 antibody has no effect on proliferation in the MLR, in particular of the MRC OX-8+ cells. The generation of cytotoxicity in the MLR is blocked by MRC OX-8 IgG and F(ab')2 and requires interaction of responder cells with the antibody during the first 24 hr of the MLR, indicating that it is the early stages which are most affected. MRC OX-8 has no effect on cytotoxic T cell function when added at the effector stage of the 51Cr-release assay and has no effect on NK cell-mediated killing.