Mechanisms of in vivo generation of cytotoxic activity against allograft. I. Local differentiation of mature cytotoxic T lymphocytes in rejection of allogeneic lymphocytes

Drug-induced tolerance to allografts in mice II. Tolerance to tumor allografts of large doses associated with rejection of skin allografts and tumor allografts of small doses

Antigen-specific tolerance to tumor allografts in mice was obtained by stimulation with allogeneic spleen cell antigens and treatment with cyclophosphamide (CY) 2 days later in various strain combinations between donor mice of spleen cell antigens and recipients. In such tolerant mice, skin allografts were rejected in various combinations of the donor-recipient. Furthermore, some of the tolerant mice showed accelerated rejection of tumor allografts of small doses, even though they allowed progressive growth of the same tumor allografts of large doses. Our results suggest that the rejection of tumor allografts of large doses may depend upon a mechanism that is distinct, qualitatively or quantitatively, from that one responsible for the rejection of tumor allografts of small doses and skin allografts. One of the most important properties of lymphocytes to separate these two different mechanisms may be a capacity of clonal expansion, namely, sensitivity to CY-induced tolerance of the lymphocytes mediating allograft rejection.

Thymus-recruited peritoneal exudate T lymphocytes

The role of the thymus in the generation of antigen-reactive peritoneal exudate T lymphocytes (PETLs) was examined in mice injected with Corynebacterium parvum (C. parvum), which exerted functions as a trigger of T cell recruitment from the thymus and as an antigen to induce antigen-reactive T cells. The proliferative response of antigen-reactive PETLs was higher in sham mice than in adult-thymectomized (ATx) mice 3 weeks after injection of C. parvum. When indomethacin (INDO) was injected simultaneously with an injection of proteose peptone for collecting PETLs, the response to C. parvum decreased to an undetectable level in ATx mice, and to a low but still positive level in sham mice. The addition of PGE2 to the culture suppressed the proliferative response of PETLs from Sham mice, but did not suppress the response of ATx mice. These results suggested the existence of different subsets in antigen-reactive T cells in terms of thymus-dependency and PGE2-dependency or -sensitivity.

In vivo differentiation of cytotoxic T lymphocytes. 1. Serum factor in immunized athymic (nu/nu) mice could differentiate CTL precursor

Mature cytotoxic T lymphocytes (CTLs) were hardly detected by 51Cr-release assay in the spleen of C3H/He mice after an intravenous injection of spleen cells of C57BL/6 (B6) mice. B6-specific CTL generation was augmented by transfer of sera obtained from C3H/He mice inoculated subcutaneously with EL-4 cells of B6 origin, P815 cells of DBA/2 origin or MH134 cells of C3H/HeN origin or these injected intraperitoneally with sheep or chicken erythrocytes. Such a factor can be produced also by athymic (nu/nu) mice. Such an augmentation of cytotoxicity was detected also in the regional lymph nodes after subcutaneous injection of allogeneic spleen cells. This factor may be different from augmenting factors reported already.

Suppressive effect by cooperation of splenic and peritoneal adherent cells on generation of cytotoxic T lymphocytes

When spleen cells primed in vivo against allogeneic lymphoid cells were used as responder cells in secondary mixed lymphocyte cultures, a high degree of cytotoxicity was generated even in the absence of splenic adherent cells. However, removal of adherent cells from such primed responder spleen cells reduced the cytotoxicity to some extent. On the other hand, when these responder cells were transferred into the peritoneal cavity of irradiated syngeneic mice together with antigenic cells, unseparated responder cells generated a lower degree of cytotoxicity than did adherent cell-depleted responder cells. In an in vitro system, peritoneal adherent cells also suppressed the generation of cytotoxic T lymphocytes by unseparated responders; however they augmented the cytotoxic T lymphocyte generation by adherent cell-depleted responders. These adherent cell populations with augmenting activity became inhibitory when they coexisted. The mechanism of this inhibitory action remains unclear.