The MECA-32 antibody reacts with a dimer of 50-55–kDa subunits expressed on most or all endothelial cells in the embryonic and adult mouse, with the exception of cardiac and skeletal muscle and the brain. Normally in skeletal and cardiac muscle, MECA-32 antigen expression is limited to small arterioles and venules; however, under conditions of inflammation, it can be induced on previously non-expressing vessels in cardiac muscle. In the central nervous system (CNS), the panendothelial cell antigen expression is developmentally regulated. During embryonic development, the antigen is found on brain vasculature up to day 16 of gestation, after which it disappears. The cessation of MECA-32 antigen expression in the CNS may be associated with the establishment of the blood-brain barrier, which begins on day 16 of gestation. In the adult mouse, inflammation in the CNS can lead to re-expression of the panendothelial cell antigen.
The antibody was conjugated to BD Horizon™ BV711 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 711-nm. BD Horizon BV711 can be excited by the violet laser and detected in a filter used to detect Cy™5.5 / Alexa Fluor® 700-like dyes (eg, 712/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there may be moderate spillover into the Alexa Fluor® 700 and PerCP-Cy5.5 detectors. However, the spillover can be corrected through compensation as with any other dye combination.