Antibody W7C5 Defines a CD109 Epitope Expressed on CD34+ and CD34− Hematopoietic and Mesenchymal Stem Cell Subsets

The cell surface antigen recognized by monoclonal antibody W7C5 is expressed at low levels on human CD34(+) and CD34(-) bone marrow stem cell populations but at high levels on fetal liver CD34(+) cells. To identify the recognized antigen, we performed partial amino acid sequence and MALDI analysis of purified W7C5 antigens. The analyses revealed that MoAb W7C5 detects CD109, a recently cloned glycophosphatidylinositol-linked glycoprotein. The specificity of MoAb W7C5 was further confirmed by the selective recognition of CHO cells transfected with human CD109 cDNA.