CD74 and pulmonary arterial hypertension: Increased CD74 protein levels in IPAH ECs were previously reported from immunostaining of human IPAH tissues and western blot of isolated IPAH ECs.45 Additionally, CD74 contributed to the recruitment of peripheral blood mononuclear cells to pulmonary ECs in vitro,45 supporting the involvement of the CD74/MHC-II complex in PAH.