Psoriasis scales contain C5a as the predominant chemotaxin for monocyte-derived dendritic cells

Dendritic cells seem to be of major importance for the pathogenesis of psor iasis. They are increased in number in lesional psoriatic skin which is tho ught to be due to an increased influx from the peripheral blood regulated b y chemotaxins. Using a biological/biochemical approach we have addressed th e question whether psoriasis scale extracts contain proteinaceous chemotaxi ns for dendritic cells. Human monocytes differentiated into dendritic cells by culture with GM-CSF and IL-4 (MoDC) served as responder cells. Chemotac tic activity for MoDC was purified by several HPLC-steps. The results of ou r study show that C5a/C5a(desarg) is the major chemotactic peptide for MoDC in psoriasis scale extracts. In comparison to other stimuli such as fMLP o r monocyte chemotactic peptide 1 (MCP-1) C5a proved to be a most potent and efficient chemotaxin for MoDC. C5a co-eluted with MRP14/calgranulin B whic h is present in large amounts in psoriasis scale extracts as identified by amino acid sequencing. However, MRP14/calgranulin B did not possess any che motactic activity for MoDC. Our results provide evidence that C5a/C5a(desar g) although not specific for dendritic cells seems to be the major chemoatt ractant for these cells in lesional psoriasis skin.