T-lymphocyte recruitment and retention in lichen planus

Lichen planus (LP) is a chronic, debilitating, inflammatory disease of the skin and mucous membranes that affects 1-2% of Americans. Its molecular pathogenesis remains poorly understood, and there are no FDA-approved treatments. We performed single cell RNA sequencing on blood and affected and unaffected skin from 7 LP patients. LP affected skin exhibited a robust immune infiltrate primarily composed of CD8 T-cells. These cells were specifically recruited by cytokines secreted by both superficial and dermal layers of skin. Basal keratinocytes and fibroblasts secrete CXCL9 and CXCL10, and fibroblasts secrete CCL19. Molecular analysis of LP skin and blood samples increased our understanding of disease pathogenesis and identified CCL19 as a new therapeutic target for treatment.