 Systemic sclerosis SSc is a rare and severe disease characterised by a fibrotic process and an incompletely elucidate physiopathology. Several shared featured have been identified between SSc and another autoimmune disease, the systemic lupus erythematous SLE as an interferon-alpha signature, the role of platelets and the polymorphism of OX40 ligand OX40L. In SLE, OX40L has been shown highly linked to the active form of the disease, was increased by the CD40L of platelets and induced the CD8 cytotoxicity while inhibiting the suppressive functions of regulator T lymphocytes. The third main factor of the SSc physiopathology apart from autoimmunity and fibrosis is the vasculopathy with an important role of endothelial cells EC. They turned out to be half-professional antigen presenting cells and can modulate the adaptive immunity. 