Detection of anaphylatoxin receptors on CD83(+) dendritic cells derived from human skin

Dendritic cells (DC) are recruited to sites of inflammation for the initiat ion of immune responses. As the anaphylatoxins C5a and C3a are important me diators of inflammation, we investigated the expression of their receptors (C3aR and C5aR) on human DC. DC were isolated from human skin or generated from purified blood monocytes and were identified by their expression of CD 1a or CD83. Freshly isolated or cultured dermal CD1a(+) and CD83(+) DC boun d anti-C5aR and anti-C3aR monoclonal antibodies (mAbs), as detected by flow cytometry. C5a induced calcium fluxes in dermal CD1a(+) and CD83(+) DC, wh ich could be inhibited by C17/5, an anti-C5a mAb. C3a did not induce calciu m fluxes in these cells. Anaphylatoxin receptor expression was down-regulat ed on dermal DC by adding tumour necrosis factor-alpha. (TNF-alpha) to the culture medium. On CD1a(+) CD83(-) cells generated from isolated blood mono cytes by culture with 6.25 ng/ml of granulocyte-macrophage colony-stimulati ng factor (GM-CSF) and 125 U/ml of interleukin-4 (IL-4), expression of both C5aR and C3aR was observed. In these cells, both C5a and C3a induced calci um fluxes. After addition of TNF-alpha to the culture medium, the majority of the CD1a(+) cells expressed CD83(+) These cells - expressing a phenotype of 'mature DC' - down-regulated the expression of the anaphylatoxin recept ors and lost their reactivity to the respective ligands. Our results demons trate the expression of the anaphylatoxin receptors C5aR and C3aR on human skin-derived DC and blood-derived cells expressing the DC-associated membra ne molecule, CD1a. Furthermore, the expression of anaphylatoxin receptors o n CD83(+) dermal DC is indicative of an intermediate stage of maturation of these cells, which was not observed on in vitro-differentiated CD83(+) cel ls.