Decreased blood CD4+PD-1+ and CD8+PD-1+ T cells in psoriatic patients with and without arthritis

Introduction
Psoriasis with and without arthritis have common immunological mechanisms which among others involve the interactions between cytokines produced by T cells, including Th1, Th17 and Th22. Although quite a lot is known about psoriasis pathogenesis, the cause of chronic immune activation and response in the disease remains unclear. One of the negative regulators of the immune system is programmed death 1 (PD-1).

Aim
To assess the expression level of PD-1 in the peripheral T cells of psoriatic patients with and without arthritis.

Material and methods
The study included 23 psoriatic patients with arthritis, 52 psoriatic patients without arthritis and 52 healthy controls. The percentages of CD3+, CD4+, CD8+, CD4+PD-1+ and CD8+PD-1+ T cells were analyzed using flow cytometry.

Results
The percentages of CD4+PD-1+ as well as CD8+PD-1+ T cells in the psoriatic patients both with and without arthritis were significantly lower than in the control group. The percentages of CD4+PD-1+ as well as CD8+PD-1+ T cells were not significantly different between the psoriatic patients with and without arthritis. A significant positive correlation between PD-1 expression on the CD4+ and CD8+ T cells was found in the psoriatic patients without arthritis.

Conclusions
Impairment of the negative co-stimulation from PD-1 may be another common characteristic of psoriasis both with and without arthritis.