Increased plasma soluble CD40 ligand concentrations in systemic sclerosis and association with pulmonary arterial hypertension and digital ulcers.

BACKGROUND Increased expression of CD40L has been reported on activated CD4+ T lymphocytes in systemic sclerosis. CD40L can be expressed in soluble form (sCD40L). OBJECTIVE To compare sCD40L concentrations in patients with systemic sclerosis and healthy controls. METHODS Quantitative sandwich ELISA was used to measure plasma sCD40L in systemic sclerosis (n = 50) and matched healthy controls (n = 20). Patients with systemic sclerosis had limited cutaneous disease (29), digital ulcers (14), pulmonary arterial hypertension (PAH) (10), pulmonary fibrosis on CT (23), positive anti-Scl70 (14), and anti-centromere antibodies (10). Calcium channel blockers were discontinued 72 hours before measurements. RESULTS Median (range) sCD40L concentration (pg/ml) was higher in systemic sclerosis than in controls (495 (10 to 7720) v 79 (50 to 118); p = 0.003), in limited cutaneous disease v diffuse disease (620 (20 to 7720) v 250 (10 to 2690); p = 0.005), in patients with digital ulcers v those without (1430 (36 to 7720) v 370 (10 to 2320); p = 0.002), and in those with PAH v those without (995 (15 to 3850) v 400 (10 to 7720); p = 0.048). sCD40L correlated with pulmonary arterial pressure estimated by Doppler echocardiography (r = 0.41; p = 0.005). CONCLUSIONS The soluble form of CD40L is increased in plasma in systemic sclerosis and may be associated with vascular complications of the disease.