Innate lymphoid cells (ILC) are important members of the skin-associated immune system. Despite their central role in healthy skin and inflammatory skin diseases, the constituent proteins of ILC have not been characterized in-depth. Here, we purified the two main human skin ILC subsets — CRTH2+ ILC2 and CRTH2–CD117+NCR2– ILC3 — from healthy skin (n=10) by flow cytometry and used state-of-the-art mass spectrometry-based proteomics for in-depth proteome analysis. For comparison, we included blood-derived ILC analogues from healthy donors in our study. We quantified 6,666 proteins using data dependent acquisition in skin derived ILC and 5,484 proteins in the blood-derived counterparts. Subsequent single run analyses using data independent acquisition revealed differential protein expression patterns between ILC2 and ILC3 in skin (619 proteins) and blood (74 proteins), including molecules of the prostaglandin-D pathway such as HPGDS and as expected CRTH2, and factors involved in migration and homing such as CCR6, ICAM-1, CD11c and CD31. Proteomes of skin versus blood ILC2 and skin versus blood ILC3 had 1557 and 2303 significant differentially expressed proteins, respectively. We also identified cytokines such as IL-16 and TGF-β1 and proteins uniquely expressed in single ILC subsets, such as CD314 in skin ILC3. This study provides a large-scale quantitative proteome of primary human ILC2 and ILC3 subsets and a resource to examine subset-specific markers and functional specialization.

ESDR195 - Proteomic Analyses of ILC2 and ILC3 from Human Skin and Peripheral Blood Reveal Distinctive Phenotypes and Functions

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING