Initial immunochemical characterization of specific macrophage-arming factor

Specific T-cell factor production and lymphocytes in the direct surroundings of a subcutaneous allogeneic tumor

Antigen-specific T-cell factors (TCF) play a role in the initiation of cellular immune responses. In allogeneic mouse-tumor models lymphocytes from the direct tumor surroundings of both euthymic and nude mice produce TCF. These lymphocytes produce TCF when collected already 1 day after subcutaneous (sc) injection of tumor cells. In contrast to euthymic mice, draining lymph nodes and spleen of nude mice did not contain TCF-producing lymphocytes at any stage after sc tumor cell injection. In sensitized euthymic mice TCF production by lymphocytes is significantly higher in the direct tumor surroundings than in draining lymph nodes or spleen. At 2 and 5 days after tumor cell injection, the mononuclear cell infiltrate of the tissue surrounding the tumor in euthymic mice showed low expression of Thy 1, CD3, TCR alpha beta, TCR gamma delta, CD4, CD8, and asialo GM1, whereas several lymphocytes and mast cells were positive for monoclonal antibody (mAb) 14-30 (directed against TCF). In both euthymic and nude mice, sc injected tumor cells showed apoptosis. In conclusion, the direct tumor surroundings are the first (and, for nude mice, the only) site of TCF production, sc injection of tumor cells attracts mAb 14-30-positive lymphocytes and renders mast cells positive for mAb 14-30.

Production of specific macrophage-arming factor precedes cytotoxic T lymphocyte activity in vivo during tumor rejection

Recently we published a hypothesis on the immunological events occurring during tumor rejection. One of the implications of this hypothesis is that specific macrophage-arming factor (SMAF) is produced early during the initiation of the immune response, whereas the "classical" cell-mediated immune response components, such as cytotoxic T lymphocytes (CTL), are produced later, that is, during the amplifier-effector phase. In this paper we establish the kinetics of the induction of (a) lymphocytes producing SMAF and (b) CTL. Groups of DBA/2 mice were injected i.p. once, twice or three times with irradiated and/or non-irradiated syngeneic SL2 tumor cells, the injections being given at intervals of 10 days. After each of these injections the production of SMAF and the expression of CTL activity were established. The results showed that in the peritoneal cavity SMAF-producing lymphocytes appeared earlier than cytotoxic lymphocytes (CTL). In addition, it was shown (a) that SMAF does not interfere with the in vitro cytotoxicity expressed by CTL and (b) that in addition to CTL memory cells, SMAF-producing memory cells were also induced after injection of syngeneic tumor cells. These data support the hypothesis that SMAF is involved in the early phase of the cellular immune response against tumors, whereas CTL are induced later.