Differences in the induction of macrophage cytotoxicity by the specific T lymphocyte factor, specific macrophage arming factor (SMAF), and the lymphokine, macrophage activating factor (MAF)

Phenotypical and functional analyses of mononuclear cells during rejection of a transplanted murine fibrosarcoma

Repeated injections of mitomycin C-treated T2 fibrosarcoma cells into tumor-sensitized mice cause regression of a secondary tumor graft and more than 90% of the mice are cured. In the data presented here, an enhancement of the cytolytic cell-mediated activities measured in vitro against the specific T2 targets is shown in lymph nodes draining the tumor and in the spleen during the process of tumor rejection. Histopathologic studies revealed a rapid and marked accumulation of mononuclear cells mostly at the periphery of the rejected tumor tissue. A significant increase of CD8-positive, asialo GM1-positive and acid phosphatase-positive cells was observed in the rejected tumors whereas CD4-positive cells were similarly detected in both progressing and rejected tumor tissue. As macrophages seemed to be the population presenting the most persistent variation after immunization, the production of TNF-alpha was studied within the tumor site and in the lymphoid tissues during the regression process. Firstly, the presence of TNF-alpha within the cytoplasm of most of the adherent cell fractions isolated from the spleen and the tumor of immune mice was demonstrated by immunocytochemistry. Next, TNF-alpha mRNA-containing cells were determined by in situ hybridization of frozen tumor sections and identified essentially as tumor infiltrating macrophages. Finally, the macrophage populations isolated from tumors and from the spleen of immune mice were able to produce in vitro large quantities of TNF-alpha without exogenous stimulation. These findings support the role of TNF-alpha in the effector mechanisms contributing to the tumor regression process.

B-cell mitogenic activity of slime products produced from slime-forming, encapsulated Lactococcus lactis ssp. cremoris

The mitogenic activities of whole cell lyophylized preparations, cell-wall components, and slime products obtained from Lactococcus lactis ssp. cremoris KVS20 were examined on murine spleen cells. Whole cell lyophylized preparations and slime products significantly (P < .05) stimulated mitogenic responses of the cells. The highest activity was induced by slime products in which the optimal concentration was 116 microg/ml. The significant (P < .05) increase of mitogenic activity induced by slime products occurred at 24 h, and the peak response was obtained 48 h after the stimulation. The activity was much higher in the fraction enriched with B cells than in the fraction enriched with T cells. In addition, slime products induced mitogenic activity to spleen cells of athymic nu/nu mice. The chemical analysis of lipopolysaccharide and the minimal concentration for mitogenic response eliminated the possibility that the activity of slime products may be due to the contamination of lipopolysaccharide. The data demonstrate that slime products are a potent B-cell-dependent mitogen.

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.