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 ( S. aureus ). Emerging evidence suggests a role for S. aureus in exacerbating AD skin inflammation. We have previously shown that specific glycosylation of S. aureus cell wall structures amplifies skin inflammation through interaction with Langerhans cells (LCs). However, 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 controls, alongside specific glycoanalysis of S. aureus strains isolated from the AD lesions. Our findings reveal four LC subpopulations, including two steady-state clusters (LC1 and LC1H) and two pro-inflammatory/matured subsets (LC2 and migratory LCs). The latter two subsets were enriched in AD skin. AD LCs showed enhanced expression of C-type lectin receptors, the high-affinity IgE receptor (FcεR1), and activation of prostaglandin and leukotrienes biosynthesis pathways, as well as upregulated transcriptional signatures related to T cell activation pathways and increased expression of CCL17 (specifically LC2) compared to healthy LCs. Correspondingly, T helper 2 and regulatory T cell populations were increased in AD lesions. Our study provides proof-of-concept for a role of LCs in connecting the S. aureus -T cell axis in the AD inflammatory cycle. ### Competing Interest Statement CMB declares speaker fee from AbbVie and Eli Lilly. LvdG declares speaker fee from AbbVie and Sanofi. NvS declares fee for service and speaker fee from MSD and GSK (paid directly to the institution) and personal revenue from a licensed patent (University of California San Diego, co-inventor Prof. V. Nizet; S. pyogenes vaccines) outside the submitted work. Other authors declare no competing interest. ### Funding Statement This work was funded by an Infection & Immunity Boost Grant from UMC Utrecht to F.v.W., M.d.B. and N.v.S. and by the DRESSCODE project (project number 09150181910001) of the Vici Talent program to N.v.S., which is financed by ZonMW. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Medical Ethical Committee of University Medical Center Utrecht, Utrecht, the Netherlands, gave ethical approval for this work (approval number 12-407). Abdominal or breast ex vivo human skin was obtained from local hospitals after cosmetic surgery. The procedure was according to the ethical principles of the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The RNA sequencing data that was obtained during this study have been deposited in NCBI’s Gene Expression Omnibus (GEO) and are accessible through GEO series accession number GSE266239. * AD : Atopic Dermatitis S. aureus : Staphylococcus aureus LCs : Langerhans cells Th2 cell : T helper 2 cell β-GlcNAc : β-linked-N-acetylglucosamine WTA : wall teichoic acid EASI : Eczema Area and Severity Index FcεR1 : high-affinity IgE receptor HSP : heat shock protein DEG : Differentially Expressed Gene GSEA : Gene Set Enrichment Analysis.