Pathogenic CCR6+ dendritic cells in the skin lesions of discoid lupus patients: a role for damage-associated molecular patterns.

Background: Discoid lupus erythematosus (DLE) is a cutaneous autoimmune inflammatory disease in which the role of conventional dendritic cells (cDCs) in skin damage has not been evaluated. Objective: To evaluate the involvement of cDCs in DLE pathogenesis. Material & Methods: Skin biopsies from 42 patients with DLE were embedded in paraffin or placed in culture. The dermis was separated and cell suspensions were characterized by flow cytometry. Results: We found an increase in cDCs with inflammatory characteristics in the skin of DLE patients, compared with control skins. Interestingly, cDCs from the DLE patients expressed low levels of the inhibitory molecule PD-L1 and showed a high expression of CCR6, which correlated with disease activity. Increased cellular death was observed in the skin of DLE patients compared with control skin and remarkably we found that damage-associated molecular patterns could be responsible for CCR6 expression on cDCs in the skin. Conclusions: Our results indicate the presence of pathogenic CCR6(+) cDCs in the skin lesions of DLE patients, which could result from in situ phenotypic changes.