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.