Microheterogeneity in regulatory circuits for T-cell alloresponsiveness

Mixed leucocyte cultures of responder spleen cells from individual B10 mice, challenged with irradiated allogeneic B10.D2 or B10.BR spleen cells, were used to generate discrete pools of cytotoxic T lymphocytes (CTL) with which to immunize (B10 x B10.D2)F1 or (B10 x B10.BR)F1 animals. Aliquots of the original donor B10 spleen cells were stored at -70 degrees. Eighteen days after immunization of the F1 animals, spleen and serum preparations from these mice were tested, in reciprocal fashion, for their ability to affect the development of CTL from the thawed donor B10 spleen lymphocytes in fresh cultures challenged with either the original or a third party allogeneic stimulus. Evidence for individual specific suppression by F1-T lymphocytes or by F1-serum (antibody) molecules was obtained. By priming (B10 x B10.D2)F1 mice with B10 lymphoid cells the F1 animals can also be shown to resist the otherwise lethal GvHD induced by sublethal whole body irradiation followed by intravenous challenge with B10 lymphoid cells. Using F1 mice primed and subsequently challenged with lymphocytes prepared from individual donors, self-preference in the regulation of GvHD was also seen. A similar fine specificity of regulatory cells was observed using suppressor cells from individual mice rendered neonatally tolerant of histocompatible cells (by inoculation of F1 hybrid cells within 24 hr of birth). These findings suggest that the mouse T cell alloreceptor repertoire is subject to a process of somatic diversification during normal ontogenesis. By examining the regulation of alloresponsiveness in T lymphocytes of B10.Br origin which differentiate from the appropriate stem cells in a B10 or B10.Br host, we have uncovered evidence that the T-cell alloreceptor repertoire is, in part at least, determined by the host MHC environment.