The human VEGF family consists of VEGF (VEGF-A), VEGF-B, VEGF-C, VEGF-D, and placental growth factor (PIGF). The VEGF family of receptors consists of three protein-tyrosine kinases (VEGFR1, VEGFR2, and VEGFR3) and two non-protein kinase co-receptors (neuropilin-1 and neuropilin-2). These components participate in new blood vessel formation from angioblasts (vasculogenesis) and new blood vessel formation from pre-existing vasculature (angiogenesis). Interaction between VEGFR1 and VEGFR2 or VEGFR2 and VEGFR3 alters receptor tyrosine phosphorylation. (C) 2008 Elsevier Inc. All rights reserved.