In murine models of Sch-PAH,codeletion of the TH2 cytokines IL-4 and IL-13 protects against thedevelopment of experimental PH, which is thought to be related to IL-13-mediatedupregulation of TGFb with consequent SMAD2/3 activation and PASMC proliferation[159, 160]. This evidence concerns the gene SMAD2 and pulmonary arterial hypertension.