MECHANISMS OF CYTOPENIA IN HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Human immunodeficiency virus (HIV) infection often has effects on the hematopoietic system which can be distinguished from the concurrent ef fects of medications or opportunistic infections. Exactly how the viru s mediates these effects remains uncertain, but both in vivo and in vi tro studies have pointed up possible direct and indirect modes of hema topoietic suppression. Whether a significant fraction of CD34+ cells i n vivo are infected with HIV remains controversial, but most studies u sing in situ polymerase chain reaction techniques would suggest not. O ther more indirect modes of hematopoietic cell suppression such as pro duction of autoantibodies, production of other humoral inhibitory fact ors, T-cell mediated suppression of hematopoiesis, or production of in hibitory or stimulatory cytokines may also be contributory. It is prob able that several of these mechanisms may occur simultaneously, and an increased understanding of their role may lead to improved strategies to correct the cytopenias which often accompany HIV disease.