Reduced CD26bright expression of peripheral blood CD8+ T-cell subsets in psoriatic patients

Abstract: Background: T cells have been shown to be highly relevant in psoriasis. CD26 is a novel T‐cell activation marker involved in various T‐cell functions, e.g. (i) co‐stimulation, (ii) migration and (iii) T‐cell memory response. In particular, CD26bright peripheral blood T cells have been shown to be altered in several autoimmune diseases. Objective: To characterize CD26‐expression of T‐cell subsets in psoriatic patients compared to healthy subjects. Methods: Peripheral blood was obtained from 15 untreated patients with severe psoriasis and from nine healthy subjects. The presence of specific CD26‐related T‐cell subsets was assessed by flow cytometry. Results: The CD26bright expression of CD8+ lymphocytes revealed a statistically significant (P<0.05) decrease in psoriatic patients. The majority of CD4+CD26bright cells are CD45RO+, whereas the minority of CD8+CD26bright cells are CD45RO+ in both groups. Conclusions: The present study demonstrates that the CD8CD26bright T‐cell population is markedly decreased in peripheral blood of psoriatic patients. Moreover, CD26 expression did not show a restriction to memory T cells. As CD26 is of relevance for T‐cell functions, future investigations should focus on elucidating these functions in psoriasis. It is attractive to speculate that the reduction in the CD8CD26bright subpopulation may represent a biomarker for recompartimentalization of activated T cells and a reduced CD8CD26bright count may correlate with increased responsiveness to T‐cell targeted treatments.