NRP1 and idiopathic pulmonary fibrosis: As SEMA class 3 proteins, including SEMA3B, necessitate the presence of coreceptor moieties NRP1 or NRP2 before interacting with their signal transducing receptors plexins A1-4, we assessed whether the expression of the SEMA3B coreceptor NRP1 and NRP2 was also perturbed in the lungs of IPF compared with those of healthy controls (36).