Differentiation and malignancy of haemopoietic progenitor cells

H-2 gene products are of central importance in immune recognition, and account for the strong transplantation resistance observed between mouse strains. Murine embryonal carcinomo (EC) cells are the tumourigenic stem cells of teratocarcinomas, and they elicit strong transplantation resistance in some allogeneic mouse strains (1) but do not express H-2 antigens. Since it is generally believed that all T cells recognize major histocompatibility complex (MHC) products, the failure to demonstrate murine cytolytic T cell lysis of EC cells under a variety of conditions is not surprising. This includes the use of lectin-dependent and cell-mediated cytotoxicity (LDCC) (2), a procedure capable of revealing the total cytolytic potential of stimulated murine T cell populations regardless of specificity. In contrast to these findings, the results presented here show that xenogeneic rat cytotoxic T cells can lyse EC cells in LDCC, and, further, that rat cytotoxic T cells generated by stimulation with mouse spleen cells in vitro can lyse murine embryonal carcinoma cells directly (3). These results prompted a re-evaluation of potential murine T cell lysis of EC cells. Murine cytotoxic T cells lytic for EC cells could be generated by immunisations and in vitro mixed lymphocyte cultures which are consistent with recognition of determinants coded by the Qa-Tla region. These results and other serological observations suggest that EC cells express MHC-class I related molecules probably specified by genes at the Qa-Tla region of chromosome 17.