Significance of IL-17A-producing CD8+CD103+ skin resident memory T cells in psoriasis lesion and their possible relationship to clinical course

Background: A number of studies have shown the relationship between the pathogenesis of psoriasis and skin resident memory T (T-RM) cells. Objective: To investigate the cytokine profile of T-RM cells from skin lesions of psoriasis and the relationship of skin T-RM cells to the future clinical course of psoriasis. Methods: We used stocked samples of T cells that were ex vivo expanded from skin biopsies of 10 patients with psoriasis vulgaris. A half of 4-mm punch biopsy specimens was subjected to expansion of skin-infiltrating T cells using IL-2 and anti-CD3/CD28 antibody-coated microbeads. More than 10(6) T cells per specimen were stocked at -80 degrees C. Defrosted cells were subjected to flow cytometric analysis. Another half of skin biopsies were subjected to immmunofluorescence staining for CD103 and other markers. Results: The biopsied skin revealed CD8(+)CD103(+) T-RM cells were present in the epidermis of psoriasis and associated with acanthosis. Sorted CD103(+) T cells were mostly CD8(+) memory T cells expressing CD69 with a skin-homing potential. A part of CD8(+)CD103(+) T cells produced interferon-gamma, IL-17A or IL-22. Notably, CD8(+)CD103(+) T-RM cells more frequently produced IL-17A than did CD8(+)CD103(-) T cells. We retrospectively divided the 10 cases into the non-advanced therapy group, and the advanced therapy group in which systemic biologics or others were initiated within one year. The frequency of CD8(+)CD103(+)IL-17A(+) T-RM cells tended to be higher in the advanced therapy group. Conclusion: These results suggest that IL-17A-producing CD8(+)CD103(+) T-RM cells are associated with a progressive clinical course of psoriasis. (C) 2019 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.