S100B and pulmonary arterial hypertension: HIV-1 infection is known to stimulate monocyte/macrophages and lymphocytes to secrete elevated levels of cytokines, growth factors and viral proteins such as Nef, Tat and gp-120, [10-16] that can then initiate endothelial injury, SMC proliferation and migration, leading to the development of HIV-PAH [8-10,18,26,48].