Drug-induced tolerance to allografts in mice. X. Augmentation of split tolerance in murine combinations disparate at both H-2 and non-H-2 antigens by the use of spleen cells from donors preimmunized with recipient antigens.

In a fully allogeneic murine combination of C3H/HeSlc (C3H) (H-2k) and C57BL/6CrSlc (B6) (H-2b), C3H mice were primed i.v. with 1 X 10(8) spleen cells from B6 mice preimmunized i.v. with 5 X 10(7) C3H spleen cells and then were given i.p. 200 mg/kg cyclophosphamide (CP) 2 days later (Im-B6-Sc plus CP group). The tolerant state in those recipient mice was compared with that in mice made tolerant conventionally with 1 X 10(8) naive B6 spleen cells plus 200 mg/kg CP (naive-B6-Sc plus CP group). B6 skin was rejected in an almost normal fashion in both the naive-B6-Sc plus CP group and the Im-B6-Sc plus CP group. However, EL4 tumor allografts (B6 origin) inoculated after complete rejection of B6 skin grafts were specifically accepted in both groups. Moreover, the tumor growth in the Im-B6-Sc plus CP group was faster than that in the naive-B6-Sc plus CP group. Mixed lymphocyte reaction, cytotoxic T lymphocyte activity, and antibody production against the tolerogen were depressed more profoundly in the Im-B6-Sc plus CP group than in the naive-B6-Sc plus CP group. These observations were consistent with the results from tumor allografting. The other immunological parameters examined in the present study, including helper T cell activity and delayed foot-pad reaction, were retained in the Im-B6-Sc plus CP group at the same levels as in the naive-B6-Sc plus CP group. These observations were consistent with the results from skin allografting. In conclusion, tumor allograft tolerance was made more profound by the use of spleen cells from donors preimmunized with recipient antigens as the tolerogen than by the use of naive spleen cells. However, skin allograft tolerance was not achieved at all by these same treatments. The contribution of graft-versus-host disease to this phenomenon was excluded by the chimeric analysis in AKR/JSea (H-2k) mice given the preimmunized (with AKR antigens) B6 spleen cells plus CP. These results strongly support the existence of a less proliferative lymphocyte population which does not evoke cell divisions to mature even after the strong stimulation with the preimmunized spleen cells and is resistant to tolerance induction.