Development of a model system for analysing graft-versus-host-mediated immune suppression

F1 hybrid mice injected with parental T lymphocytes undergo a graft-versus-host (GvH) reaction, one of the consequences being a highly depressed cytotoxic T-lymphocyte (CTL) potential against alloantigens and modified self antigens. In the present study we demonstrate that concanavalin A (Con A) can be used for analysing such GvH-mediated immune suppression. Thus, both alloantigen- and Con A-induced responses were reduced by approximately 80% in F1 suppressed (F1s) animals as compared to F1 control (F1c) mice. Although interleukin 2 (IL-2) production was found to be reduced by approximately 50% it did not account for the reduced CTL response in F1s mice. The addition of IL-2 to Con A-stimulated F1s spleen cell cultures did not reconstitute the response. The results suggest that the suppressive mechanism operates by preventing a large fraction of Lyt-2+ CTL precursors from acquiring IL-2 reactivity. However, a small fraction of CTL precursors, escaped the suppression and differentiated into effector CTL.