Soluble CD163 inhibits phorbol ester-induced lymphocyte proliferation

CD163 is a member of the scavenger receptor cysteine-rich family which is e xpressed exclusively on human monocytes and macrophages. Upon an inflammato ry stimulus the protein is shed rapidly from the membranes' surface. CD163 expression is significantly upregulated by glucocorticoids and IL-10. While the membrane-bound form of CD163 was recently identified as scavenger rece ptor for hemoglobin-haptoglobin complexes, there is no information about a possible role of the shed soluble CD163. It has been suggested earlier that CD163 plays a pivotal role in the downregulatory phase of inflammation. Ho wever, it has remained elusive so far as to how this protein might influenc e the inflammatory process. We have now identified a potential direct anti- inflammatory effect mediated by soluble CD163. The highly purified protein statistically significantly inhibits phorbol ester-induced human T-lymphocy te activation, thus attenuating the immune response to the inflammatory med iator. (C) 2001 Academic Press.