Potential role of chemerin in recruitment of plasmacytoid dendritic cells to diseased skin

Interferon α-producing plasmacytoid dendritic cells (pDC) are crucial contributors to pro-inflammatory or tolerogenic immune responses and are important in autoimmune diseases such as psoriasis. pDC accumulate in the lesional skin of psoriasis patients, but are rarely found in the affected skin of patients with atopic dermatitis (AD). While homeostatic chemokine CXCL12 and inducible pro-inflammatory CXCR3 chemokine ligands may regulate pDC influx to psoriatic skin, the mechanism responsible for selective pDC recruitment in psoriasis vs. AD remains unknown. Circulating pDC from normal donors express a limited number of chemoattractant receptors, including CXCR3 and CMKLR1 (chemokine-like receptor 1). In this work, we demonstrate that circulating pDC from normal donors as well as psoriasis and AD patients express similar levels of CXCR3 and responded similarly in functional migration assays to CXCL10. We next found that blood pDC from normal, AD, and psoriasis patients express functional CMKLR1. In contrast to normal skin, however, lesional skin from psoriasis patients contains the active form of the CMKLR1 ligand chemerin. Furthermore, in affected skin from psoriatic patients the level of active chemerin was generally higher than in AD skin. Taken together, these results indicate that local generation of active chemerin may contribute to pDC recruitment to psoriatic skin.