Generation of H-2-restricted cytotoxic T cells by ultraviolet light-treated trinitrophenyl-modified syngeneic cells: increased requirement for adherent cells.

Metabolically inactive (ultraviolet light- [UV] irradiated) cells are incapable of serving as allogeneic stimulators in a mixed lymphocyte reaction (MLR). The reason for the requirement of metabolic activity is not known. Now we have used UV-irradiated, trinitrophenyl- (TNP) coupled syngeneic spleen cells as stimulators in vitro to generate TNP-specific cytotoxic T cells (CTL). It was found that UV-irradiated cells were stimulatory only if adherent cells (nylon wool [NW] and carbonyl iron-adherent Thy-1-) were present in the responder cell population. Nonadherent allogeneic cells were also able to augment the CTL response to UV-irradiated stimulators, suggesting that the requirement for adherent cells can be replaced by the nonspecific stimulatory effects of a MLR. When spleen cells from mice primed in vivo with TNP-coupled syngeneic cells were used in vitro, it was noticed that UV-irradiated stimulators were able to induce as strong a secondary CTL response as metabolically active stimulators but this response was also entirely dependent on the presence of adherent cells in the responder cell population. As a summary, these results suggest that metabolically inactive haptenated stimulators do not present the necessary proliferative (?) stimulus to the CTL precursor cells, but this 9signal9 can be mediated via the adherent cell population, thus offering an explanation for the significance of this cell type in CTL responses in vitro.