INFLUENCE OF SURAMIN ON THE EXPRESSION OF FC-RECEPTORS AND OTHER MARKERS ON HUMAN MONOCYTES AND U937 CELLS, AND ON THEIR PHAGOCYTIC PROPERTIES

Suramin, a polyanionic and polycyclic compound, was initially used for the treatment of trypanosomiasis and onchocerciasis. In the last deca de, it has been used in therapy of cancer and acquired immune deficien cy syndrome (AIDS). The influence of suramin on the expression of vari ous markers by human mononuclear phagocytes is not known and was, ther efore, presently investigated. Suramin inhibited the proliferation of U937 cells and mitogen-induced T-cell proliferation in a dose-dependen t manner. The constitutive and cytokine-driven expression of Fc recept ors for IgG (Fc gamma RI and Fc gamma RII), IgE (Fc epsilon RII) and I gA (Fc alpha R) on blood monocytes and U937 cells was suppressed by su ramin. The basal level, as well as cytokine-induced major histocompati bility complex (MHC) class II antigens, was markedly diminished on sur amin-treated monocytes. Furthermore, suramin dramatically reduced expr ession of CD14 and partially reduced complement receptor type 3 (CR3) and CR4 expression on monocytes. In contrast, suramin slightly induced MHC class I antigens on monocytes and CD71 on U937 cells. The capacit y of monocytes to phagocytose IgG-sensitized ox erythrocytes, opsonize d Escherichia coli, or fluorescein isothiocyanate (FITC)-conjugated la tex beads was significantly inhibited. Northern blot analysis showed t hat the amount of Fc epsilon RII-specific mRNA was only partially redu ced, suggesting that other mechanims may be involved in the regulation of Fc epsilon RII expression. Our data demonstrate that suramin suppr esses the expression of various cell-surface structures on human monon uclear phagocytes and impairs their phagocytic capacity.