Single-cell sequencing of human Langerhans cells identifies altered gene expression profiles in patients with atopic dermatitis.

Atopic dermatitis (AD) is characterized by dysregulated T cell immunity and skin microbiome dysbiosis with predominance of Staphylococcus aureus, which is associated with exacerbating AD skin inflammation. Specific glycosylation patterns of S. aureus cell wall structures amplify skin inflammation through interaction with Langerhans cells (LCs). Nevertheless, the role of LCs in AD remains poorly characterized. Here, we performed single cell RNA sequencing of primary epidermal LCs and dermal T cells, isolated from skin biopsies of AD patients and healthy control subjects, alongside specific glycoanalysis of S. aureus strains isolated from the AD lesions. Our findings revealed 4 LC subpopulations ie, 2 steady-state clusters [LC1 and LC1H] and 2 proinflammatory/matured subsets [LC2 and migratory LCs]. The latter 2 subsets were enriched in AD skin. AD LCs showed enhanced expression of C-type lectin receptors, the high-affinity IgE receptor, and activation of prostaglandin and leukotriene biosynthesis pathways, upregulated transcriptional signatures related to T cell activation pathways, and increased expression of CCL17 compared with healthy LCs. Correspondingly, T helper 2 and T regulatory cell populations were increased in AD lesions. Complementary, we performed bulk RNA sequencing of primary LCs stimulated with the S. aureus strains isolated from the AD lesions, which showed upregulation of T helper 2-related pathways. Our study provides proof-of-concept for a role of LCs in connecting the S. aureus-T cell axis in the AD inflammatory cycle.