The Monoclonal Antibody W7C5 Defines a Novel Surface Antigen on Hematopoietic Stem Cells
We recently raised a monoclonal antibody, termed W7C5, against a surface antigen that is expressed at low levels on bone marrow and peripheral blood CD34+ stem/progenitor cells but at high levels on fetal liver CD34+ cells. A reasonable staining intensity was achieved using magnetofluorescent liposome conjugates to analyze expression of W7C5 antigen on CD34+CD38? bone marrow (BM) cells. Flow cytometric analyses revealed that W7C5 detects about 50% of immature CD34+CD38? BM cells that coexpressed the differentiation antigens CD164, CD133, and CD172a (SIRP?). In addition, W7C5 also recognized a CD34? BM fraction. These cells were negative for CD117 and CD133, but expressed CD45 and moderate levels of CD164. Injection of selected CD34+W7C5+ and CD34?W7C5+ cells into 5560-day-old fetal sheep resulted in an engraftment of both fractions. Partial amino acid sequence analysis of affinity-purified lysates of KU-812 cells revealed that W7C5 detects a novel membrane protein. Together, W7C5 defines a novel molecule that is expressed on CD34+ as well as on CD34? stem cell subsets.
stem cells w7c5 antigen