Human recombinant interferon alpha 2b was a kind gift from John Kirkwood, M.D. The HPASMC and HPAEC from IPAH patients as well as the control and IPAH serum were from the Pulmonary Hypertension Breakthrough Initiative of the Cardiovascular Medicine Research Fund. The gene discussed is IFNA2; the disease is idiopathic pulmonary arterial hypertension.