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

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.