Expression of the anaphylatoxin C5a receptor in non-myeloid cells

C5a, a 74 amino acid peptide cleaved from the complement protein C5, repres ents the most potent anaphylatoxin and possesses inflammatory as well as im munomodulatory acitivities. In the past, expression of the receptor for the anaphylatoxin C5a (C5aR) has been thought to be restricted to cells of mye loid origin. However, recent evidence suggests that the C5aR is constitutiv ely expressed in non-myeloid cells including epithelial, endothelial and sm ooth muscle cells in the human liver and lung. These findings are contraste d by results from our laboratory which demonstrated that in the normal huma n liver and lung C5aR expression is detectable exclusively in macrophages a nd macrophage-derived cells (Kupffer cells). Interestingly, we found eviden ce that C5aR expression may be inducible in epithelial cells as C5aR mRNA w as observed in vivo in human keratinocytes of the inflamed but not of the n ormal skin. Herein we review the work of our laboratory and others on the e xpression of the CSaR in various human non-myeloid cells types. A better un derstanding of the expression patterns of this important anaphylatoxin rece ptor may provide new insights in the pathophysiological role of C5a in vivo . (C) 1999 Elsevier Science Ltd. All rights reserved.