Impaired expression of Tim-3 on Th17 and Th1 cells in psoriasis.

Psoriasis is a chronic skin disease mediated by Th17 and/or Th1 cells. Tim-3 is a cell surface molecule preferentially expressed on Th17 and Th1 cells. The interaction of Tim-3 with Tim-3 ligand inhibits cytokine production. To assess whether T cells in psoriasis have functional abnormalities, expression of cell surface Tim-3 on blood T cells producing interleukin-17 (Th17/Tc17 cells) or interferon-γ (Th1/Tc1 cells) was examined by flow cytometry. Psoriasis patients had higher numbers of Th17 and Tc17 cells, as well as Th1 and Tc1 cells, than healthy donors. However, Th17, Th1 and Tc1 cells in psoriasis did not efficiently express Tim-3 upon activation, compared with those from atopic dermatitis and healthy donors. Tim-3- cells showed more potent cytokine production than Tim-3+ cells. Impaired Tim-3 expression allows Th17, Th1 and Tc1 cells to escape from Tim-3-mediated negative regulatory systems and may contribute to the pathogenesis of psoriasis.