Role of the mononuclear phagocyte system in the immunopathogenesis of human immunodeficiency virus infection and the acquired immunodeficiency syndrome.

In studies aimed at defining monocyte and macrophage function in patients with human immunodeficiency virus (HIV) infection, we found impaired in vivo Fc receptor-specific clearance in 20 of 25 patients with acquired immunodeficiency syndrome (AIDS) and in five of 13 patients with AIDS-related illnesses. The in vivo function of macrophage C3 receptors was also found to be abnormal: AIDS patients had a relatively large release of cell back into the circulation, suggesting failure of macrophage phagocytosis. The antibody-dependent cell-mediated cytotoxicity of circulating mononuclear cells was significantly lower in AIDS patients than in healthy controls. Monocyte nonspecific phagocytosis and surface marker expression were intact. Defective monocyte and macrophage function is an integral part of the immunopathology of AIDS, leading to the failure to control opportunistic pathogens. Whether these defects are due to intrinsic infection of the mononuclear phagocytes with HIV or are secondary to other events in the network of HIV infection remains to be determined.