Interestingly, NRP1 is known to act as a coreceptor for vascular endothelial growth factor (VEGF)-R40 in MOs/macrophage, and VEGFR expression and VEGF-mediated signalling has been associated with MO differentiation into OCs.41 42 Evaluation of RA patient serum revealed that high levels of VEGF correlate with response to TNF (figure 6F). The gene discussed is NRP1; the disease is rheumatoid arthritis.