Association of circulating receptor FcγRIII-positive monocytes in AIDS patients with elevated levels of transforming growth factor-β

Abstract

Monocytes in the circulation of normal individuals express two receptors for the constant region of immunoglobulin, FcγRI and FcγRII. In contrast, we have observed that AIDS monocytes express significant levels of a third FcγR, FcγRIII (CD16), which is normally associated with activation or maturation of the monocyte population. By dual-fluorescence analysis using a monoclonal antibody specific for FcγRIII (MAb 3G8), 38.5±3.2% of the LeuM3 (CD14)-positive monocytes in AIDS patients were CD16 positive as compared to 10.4±1.0% for healthy individuals (n = 29; P < 0.005). Furthermore, AIDS monocytes expressed FcγRIII-specific mRNA which is expressed minimally or not at all in control monocytes. As a recently identified inducer of FcγRIH expression on blood monocytes, transforming growth factor-β (TGF-β) was found to be elevated in the serum and/or plasma of AIDS patients. Moreover, incubation of normal monocytes with AIDS serum or plasma induced CD16 expression which correlated with serum TGF-β levels (r = 0.74, P < 0.001) and was inhibited with a neutralizing antibody to TGF-β. Thus, the increased CD16 expression on peripheral blood monocytes in AIDS patients may be the consequence of elevated circulating levels of the polypeptide hormone TGF-β.