Single-cell transcriptomics suggest distinct upstream drivers of IL-17A/F in hidradenitis versus psoriasis

Methods: Single-cell data of 12,300 cutaneous immune cells from 8 de-roofing surgical HS skin samples that included dermal tunnels were compared with single-cell data of psoriasis skin (19,525 cells from 11 samples) and control skin (11,920 cells from 10 samples). All the single-cell data were generated by the identical protocol. Results: HS T17 cells expressed lower levels of IL23R and higher levels of IL1R1 and IL17F compared to psoriasis T17 cells (p < 0.05). HS regulatory T-cells (Tregs) expressed higher levels of IL1R1 and IL17F compared to psoriasis Tregs (p < 0.05). Semimature dendritic cells (DCs) were the major immune cell subsets expressing IL1B in HS, and IL-1B ligand-receptor interactions between semimature DCs and T17 cells were increased in HS compared to psoriasis (p < 0.05). HS dermal tunnel keratinocytes (KCs) expressed inflammatory cytokines (IL17C, IL1A, IL1B, and IL6) different from HS epidermis KCs (IL36G) (p < 0.05). IL6, which synergizes with IL1B to maintain cytokine expression in T17 cells, was mainly expressed by fibroblasts in HS, which also expressed IL11+ inflammatory fibroblast genes (IL11, IL24, IL6, and POSTN) involved in paracrine IL-1/IL-6 loop. Conclusion: The IL-1B-T17 cell cytokine axis is likely a dominant pathway in HS with HS T17 cells activated by IL-1B signaling, unlike psoriasis T17 cells which are activated by IL-23 signaling. Clinical Implication: Biologics targeting IL-17 isoforms and IL-1B may be effective for HS but biologics targeting IL-23 may be less effective for HS.