Role of the mononuclear phagocyte system in the development of acquired immunodeficiency syndrome (AIDS).

This review describes current understanding of the role of cells of the mononuclear phagocyte system in the development of acquired immunodeficiency syndrome (AIDS). Monocyte-macrophage like cells have been shown to harbor human immunodeficiency virus type 1 (HIV-I) infection in both peripheral blood and bone marrow as well as in target organs such as brain, lungs, lymph nodes, and skin. Mononuclear phagocytes that have been infected by HIV-I do not undergo significant cytopathic changes, suggesting that they may be important viral reservoirs. These and related cells may also promote the slow, persistent nature of HIV-I infections by escaping host immunologic surveillance mechanisms. There is evidence that HIV-I infections in monocytes and premonocytes can initially be latent but progress to an active viral replication state upon differentiation and/or maturation. Functional abnormalities in the mononuclear phagocyte system following infection by HIV-I have also been described, and these may be partially responsible for the severe immunosuppression characteristic of AIDS and AIDS-related disorders. These defects may be mediated by quantitative and qualitative changes in the T-helper population. Although the role of mononuclear phagocytes as viral reservoirs and as mediators of immunosuppression is still largely speculative, increasing evidence suggests that these cells influence the course of HIV-I infections.