Plasmalemma vesicle-associated protein (PLVAP), also known as PV-1, PAL-E and MECA-32 antigen, is an endothelial cell-specific type II membrane N-glycosylated glycoprotein with a molecular weight of approximately 50-65 kDa, that forms homodimers in situ (PMID: 7626790; 30231925). The MECA-32 antibody, derived from rats immunized with murine lymph node stroma, shows high specificity for mouse endothelium in both embryonic and mature tissues (PMID: 2683264; 7626790). It recognizes most endothelial cells in the embryonic and in the adult mouse, with the exception of the brain, skeletal, and cardiac muscle, where the MECA-32 antigen has a more restricted distribution. In skeletal and cardiac muscle only small arterioles and venules express the MECA-32 antigen, while in the brain its expression is negatively correlated with the differentiation of the vasculature to form the blood brain barrier (PMID: 7626790).