In addition, estrogen influences B cell maturation andselection and may account for the differences observed in, EBV-immortalizedcells and in males and females.124 Furthermore, the BMPR2 ligands, BMP2 and BMP4, also have roles in thedevelopment, growth potential and apoptosis of B cells.125 As the B cells studied were from HPAH patients with dysfunctional BMPR2signalling, they may be phenotypically altered, resulting in changes to estrogenmetabolism and differential expression of CYP1B1 compared to human PASMCs fromHPAH patients. This evidence concerns the gene CYP1B1 and heritable pulmonary arterial hypertension.