The in vitro killing of syngeneic cells by peritoneal cells from adjuvant-stimulated mice

The production of a cytotoxic factor by mouse peritoneal macrophages and macrophage hybridomas treated with various stimulating agents

Murine peritoneal macrophages elicited with a streptococcal preparation, OK-432, produced as much of a cytotoxic factor after stimulation with lipopolysaccharide (LPS) as BCG-elicited macrophages did. Proteose peptone-elicited macrophages produced a very small amount, if any, of the factor, and resident peritoneal macrophages did not release it at all even after LPS-stimulation. A newly established macrophage hybridoma, D/O-3.3, produced the factor after LPS-stimulation, but another hybridoma, D/O-3.2, did not. Experiments using these peritoneal macrophages and macrophage hybridomas demonstrated that macrophages can be divided into three subpopulations with regard to stages of activation for production of the cytotoxic factor. The first is fully activated macrophages which produce the factor after stimulation with LPS or MAF-C alone, the second is partially activated macrophages which produce the factor only after stimulation with a combination of recombinant interferon-gamma (rIFN-gamma) and LPS or rIFN-gamma and macrophage activating factor for cytotoxicity (MAF-C), and the third is nonactivated macrophages which cannot produce the factor at all.

Radiation therapy and Corynebacterium parvum in the treatment of murine tumors

The relative effectiveness of local irradiation alone or combined with Corynebacterium parvum (C parvum) treatment has been investigated employing four tumors: a mammary carcinoma (MCa) (nonimmunogenic), a fibrosarcoma (moderately strongly immunogenic), and two squamous cell carcinomas (SCC-2 being weakly and SCC-4 being very weakly or nonimmunogenic). C parvum treatment was started when the isotransplanted tumor growing in the mouse leg was 5 mm in diameter and the local irradiation was administered to 8-mm diameter tumor. Effect of the combined treatment was barely evident with the MCa but strongly present in FSa; up to 60% of mice were cured of FSa by C parvum alone and the response to low radiation dose, e.g., 200 rads, was highly increased. For SCC-2 the TCD50 was approximately 7000 rads and 3000 rads in control and test mice, respectively. Comparable values for SCC-4 were 7700 and approximately 5500 rads. Importantly, for SCC-4 there was a large and highly significant reduction in the proportion of mice that died of metastases to lung but were free of evident tumor at the primary site.

Lymphocyte activation by cell separation procedures

Cell separation techniques normally used to obtain subpopulations of lymphocytes were shown, under certain conditions, to render the cells cytotoxic towards a number of target-cells including autologous lymphocytes. To cause cytotoxicity, it was necessary to pass cells through glass wool and/or nylon wool columns equilibrated with media containing fresh plasma or serum. Cells lost activation upon overnight in vitro culture or treatment with trypsin. In addition to direct cell cytotoxicity, cells released heat labile cytotoxic factors and antibody during the separation procedures. The implications of the results for the interpretation of cell separation studies designed to attribute immunological effects to one or another cell type were discussed.

Activated macrophages release a factor which lyses malignant cells but not normal cells

When rat macrophages are activated by exposure to bacterial endotoxin they acquire the capacity to lyse sarcoma cells in tissue culture. Although showing no immunological specificity this lytic effect was only detectable on malignant cells; normal cells were unaffected. This tumor-selective lytic effect is mediated by a labile supernatant product.