Studies on in-vivo priming of the trinitrophenyl-reactive cytotoxic effector-system. III. Are helper T cells involved in the in-vitro generation of cross-reactive as well as restricted cytotoxic responses?

The present study investigates the role of helper cells from trinitrophenyl(TNP)-primed mice in the generation of cytotoxic T lymphocytes (CTL) which lyse TNP-modified syngeneic (TNP-self) targets and cross-reactively lyse TNP-allogeneic target cells. Anti-TNP CTL activities generated from primed (either by intraperitoneal injection of TNP-syngeneic cells or by skin painting with trinitrochlorobenzene) and unprimed spleen cells were compared. When effector populations with comparable lytic activities on TNP-self targets were tested against allogeneic TNP-modified targets, only the in vivo primed effector cells displayed significant cytotoxicity. Since radioresistant helper cells have been found to enhance the anti-TNP-self CTL response, the question was raised whether this helper population could be shown to be involved in the enhanced TNP-allogeneic cross-reactive lysis. Normal spleen cells co-cultured with radioresistant helper cells failed to induce any detectable lysis on TNP-allogeneic targets under conditions for which these helper cells did enhance the lysis detected on TNP-self targets. These results suggest that triggering of such TNP-cross-reactive effector cells during the in vivo priming stage is responsible for the in vitro generation of cross-reactivity.