The role of chemerin in the colocalization of NK and dendritic cell subsets into inflamed tissues

Chemerin is a chemotactic agonist recently identified as the ligand of ChemR23, a serpentine receptor expressed by mononuclear phagocytes and dendritic cells (DCs). This study shows that blood CD56^lowCD16⁺ natural killer (NK) cells selectively express functional ChemR23 and that this receptor is coexpressed with CXCR1, the CXCL8 receptor, and the KIR receptors. In vitro culturing of NK cells with IL-2 or IL-15 induced a delayed and time-dependent down-regulation of ChemR23 that was associated with the inhibition of NK cell migration to chemerin. Biopsies obtained from patients with oral lichen planus presented an infiltration of CD94⁺CD3 ^-CD56⁺ NK cells that coexpressed ChemR23. The same biopsies were infiltrated by myeloid, DC-SIGN⁺ and plasmacytoid, CD123⁺BDCA2⁺, ChemR23⁺ dendritic cells that were occasionally associated with NK cells. In the same histologic sections, chemerin was expressed by inflamed dermal endothelium. These findings propose a role for the ChemR23/chemerin axis in the recruitment of blood NK cells and strongly implicate chemerin as a key factor for the colocalization of NK cells and DC subsets in pathologic peripheral tissues.