VWF and systemic sclerosis: In this study we evaluated the expression of LFA-1, VLA-4 and L-selectin antigens on circulating T cells and serum levels of soluble vWF, ICAM-1, VCAM-1 and P-selectin in patients with SSc with associated PAH, at baseline and after 12 months of bosentan therapy, as compared to patients with SSc without PAH and healthy subjects.