CD40L is a costimulatory molecule and an early activation marker of T-lymphocytes. Based on the hypothesis that activated T-cells may play a role in the pathogenesis of psoriatic arthritis (PsA), we evaluated the level of CD40L expression on T-cells from patients with PsA.
We analysed 12 patients with PsA, six patients with rheumatoid arthritis (RA) and four healthy volunteers. T-cell surface expression of CD40L was evaluated using two-colour flow cytometry in (i) the resting state and (ii) following stimulation with phorbol myristate acetate/ionomycin, with or without ciclosporin (CsA)-mediated inhibition.
Expression of CD40L was significantly increased on activated T-cells from patients with PsA, particularly those with active disease, when compared with normal individuals and patients with RA (mean percentages of CD3+ CD40L+ cells: 23.74, 11.59 and 9.57% for patients with active PsA, patients with RA and healthy volunteers, respectively). CsA-mediated inhibition of CD40L induction was equally effective in all study groups.
CD40L is overexpressed on T-cells from patients with active PsA. This may indicate a role for CD40L in PsA pathogenesis. Larger-scale studies are warranted to address these issues.