Antigenic and genetic parameters in the stimulation and in the lytic phases of anti-hapten + self cytotoxic T cells and their derived clones: role of the T helper cell.

Requirements for stimulation of cytotoxic T cells (CTL) and for their lytic recognition have been compared in T cell lines repeatedly stimulated with trinitrobenzene sulfonate-treated syngeneic murine spleen cells. Differences were observed between the requirements for cells to stimulate or to be lysed by the CTL, which included: (a) the expression of major histocompatibility complex (MHC = H-2) encoded allelic products, and (b) the hapten density. Propagation of the CTL within the line required I-A intra-H-2 homology between hapten-treated stimulation cells and the line cells, whereas the lytic interaction required H-2K region homology between hapten-treated target cells and CTL. The hapten density requirement was analyzed for a responder (H-2k) and a non-responder (H-2b) strain to low hapten density modified syngeneic cells. This property was found to be a characteristic of the lytic phase rather than of the stimulation of CTL. CTL clones could be derived by growing the line cells under conditions of limiting dilution in the presence ot T cell growth factors. Such CTL clones were unable to be stimulated by their target antigens and were dependent on T cell growth factors for their propagation. These results are discussed in terms of the dependence of the development and growth of CTL on T helper cells.