A mouse endothelial cell-specific monoclonal antibody: its reactivity with LTMC endothelium.

The binding of a marrow cell-related monoclonal antibody (H513E3 MAb) has been investigated in long-term marrow cultures (LTMC) and in vivo. Immunogold labeling and electron microscopy revealed that this antibody labeled an endothelial-like cell. Cross-reaction of anti-human Factor VIII confirmed endothelial specificity of the H513E3 MAb. In addition, vessel endothelium (vena cava, aorta, and marrow) exhibited binding of the antibody. This antibody provides a unique tool to study the cellular architecture of LTMC and implicates endothelium as an important component of LTMC. The function of the endothelial cell-specific surface antigen is unknown, although preferential labeling of the upper surface of endothelial cells suggests that it may play a role in cell communication, particularly with the floating population. The H513E3 MAb reacts with an external membrane antigen, a property that makes this antibody particularly useful for fluorescences-activated sorting of endothelial cells.