Biomedical subjects

C M Zacharchuk

Publications and source records attributed to C M Zacharchuk.

21 records · Page 2Linked to original sources

PubMed1983

Mechanism of macrophage-mediated cytotoxicity: production of a soluble cytotoxic factor.

Peritoneal macrophages from C3HeB/FeJ mice became cytotoxic for 6C3HED lymphosarcoma cells, P815 mastocytoma cells, and L-929 fibroblasts when treated with the calcium ionophore, A23187, at concentrations ranging from 1.0 to 20 microM. The effect of A23187 on other activation processes was also tested. It was found that A23187 and lipopolysaccharide (LPS) acted synergistically, but no consistent synergy with macrophage-activating factor (MAF) was observed. Cytotoxic activity (M phi-CF) was found in cellfree supernatants from M phi activated by A23187 or LPS. Furthermore, these two activating agents synergize in the production of M phi-CF. The cytotoxic activity of the crude material was not blocked by catalase or protease inhibitors. Fractionation of supernatants by high pressure liquid chromatography has shown that there was a peak of cytotoxic activity with a m.w. of approximately 45,000. Interestingly, L-929 cells were 30-fold more sensitive to M phi-CF than a lymphotoxin-resistant subline of L-929.

Animals↗

PubMed1980

H-2 restriction: independent recognition of H-2 and foreign antigen by a single receptor.

We describe two situations in which the recognition of hapten can compensate for the lack of recognition of appropriate H-2 gene products in hapten-specific, H-2 restricted, T lymphocyte-mediated cytolysis. First, we show that although recognition of appropriate H-2 gene products is essential for the lysis of target cells bearing a low hapten density, significant hapten-specific lysis of H-2 inappropriate target cells is observed at high levels of target cell derivatization. Secondly, we show that hapten-conjugated anti-H-2 antibody inhibits cytolysis poorly even though its binding to target cell H-2 antigens is equivalent to that of underivatized antibody. These results suggest that hapten and H-2 are recognized independently and are therefore inconsistent with the altered-self model. Although our data do not exclude the dual-recognition model, we prefer to interpret them within the framework of a single-receptor model in which hapten and H-2 are recognized independently by receptors of identical idiotype on the T cell. We postulate that the affinity of these receptors for the relevant H-2 gene product is low enough so that the T cell is not activated by encounters with normal-self cells expressing that H-2 gene product. However, when self cells express in addition a foreign antigen that can also be recognized by the same receptor, then the force of T cell-target cell interaction may be increased sufficiently to activate T cell effector function.

Animals↗

PubMed1976

Effect of trypsin on mouse mammary tumor virus.

Undisrupted mouse mammary tumor virus (MuMTV) derived from the milk of of RIII mice has been analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electron microscopy after treatment with insolubilized trypsin. No alterations were found in viral fine structure by either freeze-etch or negative-stain electron microscopy. No alterations were found in the ability of trypsinized virus to compete in a radioimmune assay for viral antigens. Infectivity experiments indicate no significant differences in the ability of treated virus to infect C57Bl mice. However, significant differences were observed in polypeptide composition. The intensely periodic acid-Schiff-positive band, gp140, was shown by galactose oxidase-borotritide labeling to be degraded into a fragment of 125,000 molecular weight. The major glycoprotein, gp55, was split into fragments of 36,000 and 23,000 molecular weight, both of which stained with periodic acid-Schiff stain. Gp68 was removed from the virus. Experiments with purified, iodinated gp55 showed that the trypsin-induced fragments of gp55 were immunologically active. We conclude that: (i) certain glycoproteins at the surface of MuMTV are accessible to an insoluble form of trypsin, (ii) the trypsin causes a nick in the polypeptide chain without affecting the configuration of the molecule; (iii) the nicked molecules remain bound to the virus; and (iv) the presence of these nicked molecules does not interfere with the biological or antigenic expression of virus function.

Animals↗