This antibody reacts with the CD105 antigen, which is expressed by vascular endothelial cells and syncytiotrophoblasts of placenta, Pre-B cells in fetal marrow, erythroid precursors in fetal and adult bone marrow and is weakly expressed by stromal fibroblasts. Reacts with a homodimeric integral membrane protein comprised of 95Kd subunits (CD105). CD105 is a component of the TGF-B receptor system and can bind TGF-B1 and TGF-B3 with high affinity but does not bind TGF-B2. U937 cells and monocytes and tissue macrophages also expresses CD105. Expression of CD105 is increased on activated endothelium in tissues undergoing angiogenesis, such as in tumours, or in cases of wound healing or dermal inflammation.