Human thymic and peripheral blood non-MHC-restricted cytotoxic lymphocytes.

We propose that non-MHC-restricted cytotoxicity is mediated by two distinct types of lymphocyte: NK cells and a unique subset of cytotoxic T-lymphocytes (CTLs). Herein, we review experimental data to support the hypothesis that NK cells and non-MHC-restricted CTLs use different recognition structures and arise from distinct lineages. Furthermore, we demonstrate that non-MHC-restricted CTLs can be generated in vitro by culturing thymocytes in recombinant interleukin-2 (rIL-2).