Model of immune regulation contributing to vascular health and immune dysregulation favoring vascular disease following endothelial injury. In this model, endothelial injury causes a local immune response. With normal immune regulation, vascular injury does not culminated in pulmonary vascular remodeling and PAH. The absence of normal immune regulation results in an inappropriately exuberant inflammatory response, accelerated endothelial cell apoptosis, smooth muscle hypertrophy, and increased pulmonary vascular resistance.