Preferential expression of αEβ7 integrin (CD103) on CD8+ T cells in the psoriatic epidermis: regulation by interleukins 4 and 12 and transforming growth factor‐β

SummaryBackground  Intraepidermal T lymphocytes are a critical element for sustaining the lesional pathology of psoriasis. Integrin αEβ7 (CD103), a ligand for E‐cadherin, may play a role in the localization of pathogenic T cells within the epidermis of psoriatic lesions. However, little information is available regarding αEβ7 expression on intraepidermal T cells in psoriasis. Objectives  To examine αEβ7 expression on intraepidermal T cells in psoriatic lesions and the regulation of αEβ7 expression on T cells in response to cytokines. Methods T‐cell expression of αEβ7 was examined by immunohistochemistry and flow cytometry.In vitro regulation of αEβ7 expression on CD4+ or CD8+ T cells purified from peripheral blood of healthy donors was also examined. Results Immunohistochemical staining revealed expression of αEβ7 on a greater proportion of epidermal T cells than dermal T cells. Nearly 30% of intraepidermal CD4+ T cells were found to express αEβ7 on flow cytometry, whereas more than 80% of intraepidermal CD8+ T cells expressed this integrin. In contrast, few T cells expressed αEβ7 in the peripheral blood of psoriatic patients. Thein vitro culture experiment confirmed that αEβ7 was preferentially expressed on CD8+ T cells after stimulation with anti‐CD3 monoclonal antibodies. Addition of transforming growth factor‐β and interleukin‐4 upregulated αEβ7 expression on T cells, whereas interleukin 12 downregulated this. Furthermore, αEβ7 expression on established memory CD8+ T cells was not so reversible as that on CD4+ T cells. Conclusions  Preferential and stable expression of αEβ7 on CD8+ T cells may be involved in the lesional pathology of psoriasis.