Cytotoxic Lymphocytes from Rats depleted of Thymus Processed Cells

Abstract

THE mechanisms by which lymphocytes damaged antigenically foreign cells are thought to be of fundamental importance in the rejection of allografts and neoplastic cells. Studies by Cerottini, Nordin and Brunner^{1, 2} in mice sensitized to allogeneic target cells have shown that their cytotoxic activity is attributable to thymus-derived lymphocytes, which act directly on the target cell. These lymphocytes do not seem to require the cooperation of other lymphoid populations. But we have shown in rats that immunologically specific damage by lymphocytes to xenogeneic target cells requires the participation of two populations of lymphoid cells^{3, 4}. One population produced IgG specific for target cell antigens, but was not itself cytotoxic, and the other population showed cytotoxic activity against target cells, the antigens of which were complexed with specific antibody. Therefore, in this system the specificity of the cytotoxic effector cell is directed at a determinant on antibody, rather than at target cell antigen. In a previous report⁵ we presented indirect evidence which suggested that the effector lymphocyte in this antibody-dependent cytotoxic system was not thymus processed and we are now providing direct evidence for this.