In vitro generation of cytotoxic lymphocytes against radiation and radiation leukaemia virus-induced tumours. II. A radiation-induced thymoma generates cytyotoxic response in syngeneic but not in allogeneic lymphocytes.

A thymoma cell line (PXT), originally induced by X-irradiation in a C57Bl/6 mouse, was found capable of generating cytotoxic T lymphocytes (CTL) in a syngeneic mixed lymphocyte tumour culture (MLTC), but failed to stimulate allogeneic lymphocytes. Serologically defined H-2 antigens could readily be detected on PXT cells, which were also susceptible to lysis by alloreactive CTL generated against C57Bl/6 lymphoblasts or other thymomas of C57Bl/6 origin. These observations suggest that the PXT line lacks lymphocyte-activating determinants (LAD) essential for allosensitization but possesses other determinants enabling stimulation of syngeneic CTL, and that the cellular events leading to generation of anti-H-2 and anti-'modified self' CTL proceed along distinct T-cell differentiation pathways.