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 (TRM ) cells.

OBJECTIVE: To investigate the cytokine profile of TRM cells from skin lesions of psoriasis and the relationship of skin TRM 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 106 T cells per specimen were stocked at -80°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+ TRM 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-γ, IL-17A or IL-22. Notably, CD8+ CD103+ TRM 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+ TRM cells tended to be higher in the advanced therapy group.

CONCLUSION: These results suggest that IL-17A-producing CD8+ CD103+ TRM cells are associated with a progressive clinical course of psoriasis.