New monoclonal antibody B7 selectively recognizes rat myocardium microvascular endothelial cells

Myocardial microvascular endothelial cells (MMECs) play a vital role in modulating cardiomyocyte development, survival, and contraction during embryonic cardiogenesis and mature myocardium. However, specific molecular composition of MMECs is still not well known, with no special MMEC marker to distinguish microvascular endothelial cells (ECs) from macrovascular ECs. In the present study, we immunized BALB/c mice with membrane proteins of MMECs. Through screening by enzyme linked immunosorbent assay and immunohistochemistry, a new monoclonal antibody that specifically recognizes MMECs was yielded. Immunohistochemistry of tissue arrays showed that MAb B7 also selectively recognized microvascular ECs but not macrovascular ECs in other tissues. Immunofluorescence and immuno-electron microscope assay indicated that B7 antigen was a plasma membrane molecule. Interestingly, we also found that B7 antigen was dramatically decreased in diabetic rat compared with that in normal rat. In conclusion, MAb B7 not only provides a new biomarker to help us understand the molecular composition of microvascular ECs, but also indicates that B7 antigen might play an important role in the dysfunction of microvascular ECs.