In vivo and in vitro effects of anti-macrophage serum

Identification of human mononuclear cells by anti-monocyte serum

An antiserum to human leukaemic monocytes was raised in rabbits. Adsorption with human thymocytes and chronic lymphatic leukaemia cells rendered the antiserum specific for cells of the human myeloid and monocytic cell series. Additional adsorption with granulocytes left a weak, but specific, activity for monocytes. The cells in normal peripheral blood with which the antiserum reacts by an immunoperoxidase technique have typical monocyte morphology. Cells with typical lymphocyte morphology do not react with the antiserum, but a few cells with intermediate morphology were also stained by the antiserum. Using the antiserum as a marker, the precursor cells of the monocytic and myeloid cell series were traced in the bone marrow.

Effects of antithymocyte and antimacrophage sera on the survival of mice infected with Listeria monocytogenes

Antisera prepared in rabbits against purified mouse thymocytes (antithymocyte serum; ATS) and peritoneal macrophages (antimacrophage serum; AMS) were injected intraperitoneally into Balb/c mice infected with the bacterium Listeria monocytogenes. When administered near the initiation of infection, the ATS significantly decreased the survival time of the animals and increased the mortality rate. When ATS was administered 6 days after a sublethal dose of L. monocytogenes had been inoculated, an overt disease did not evolve. ATS that significantly potentiated primary listeriosis also had high cytotoxicity titers for thymocytes and lymphoid cells from the peritoneal cavity. Although cytotoxic activity against peritoneal macrophages could be demonstrated in lower dilutions of the ATS, this activity did not appear to correlate with the effects of the sera on listeriosis. The injection of AMS did not enhance the infectious process. In some trials more deaths occurred among mice receiving normal rabbit serum than those receiving AMS. All of the AMS had cytotoxic titers against peritoneal macrophages, and the sera were usually inactive against thymocytes and peritoneal lymphoid cells. Listeria was isolated from fatally infected mice with nearly equal success in all of the serum-treated groups, and the serum treatments did not appear to alter the pattern of gross lesions. The afferent limb of the immune response was markedly affected by the presence of antibodies to lymphocytes. However, antibodies reacting with macrophages did not demonstrably enhance the Listeria process, which depends upon cellular immunity as the principal means of acquired host defense.

Effect of Anti-Kupffer Cell Serum on Phagocytosis and Humoral Antibody Formation

To ascertain the effects of selective impairment of the fixed macrophage compartment on host defense, rabbit anti-rat Kupffer cell serum was raised and tested for its ability to depress phagocytosis and to serve as an immunosuppressant. The ability of the anti-Kupffer cell serum (AKS) to depress intravascular clearance rates of gelatinized RE test lipid emulsion indicated that the antiserum can functionally impair overt phagocytic activity. The phagocytic impairment was manifested by a significantly decreased liver phagocytosis of the lipid emulsion, whereas only a slight decrease in phagocytosis by the spleen was noted. When titered in vitro, AKS was cytotoxic to hepatic and splenic macrophages. Although AKS induced some degree of immunosuppressive activity, it was not as effective as antilymphocytic serum in suppressing the humoral immune response of rats to sheep red blood cells. Selectivity in the cytotoxic activity of AKS was manifested by toxicity for macrophages but not toxicity for thymocytes or splenic lymphocytes. It is suggested that AKS as a specific antimacrophage serum may be useful for assessing the contribution of the reticuloendothelial system to host defense physiology and metabolism.