CD32 EXPRESSION AND SIGNALING IS DOWN-REGULATED BY TRANSFORMING GROWTH-FACTOR-BETA-1 ON HUMAN MONOCYTES

CD32 (Fc gamma RII) is the most abundantly distributed class of IgG Fc receptors in the human body. In this study, we analyzed the effect of transforming growth factor (TGF)-beta 1, a cytokine with strong immun osuppressive function, on the expression and function of CD32 on fresh ly isolated peripheral blood monocytes and three human monocytic cell lines, U937, THP-1 and Mono mac-6. We found that TGF-beta 1 down-regul ates CD32 expression on monocytes and all monocytic cell lines in a do se- and time-dependent fashion. A mean down-regulation of CD32 express ion om THP-1 cells of 54 +/- 3.2 % after 24 h was found at a concentra tion of 1 ng/ml TCF-beta 1. At the mRNA level, TGF-beta 1 induced a tw ofold down-regulation of CD32. Cross-linking of CD32 induced an increa se in the concentration of intracellular Ca2+, which was reduced by 50 % by TGF-beta 1, suggesting a decreased downstream signaling mediated by the receptor.