AC136 recognizes the human CD34, a class III epitope of the CD34 antigen. This epitope is different than the one recognized by the clone used in the CD34 MicroBead Kits. The CD34 antigen is a single-chain transmembrane glycoprotein, expressed on human hematopoietic stem and progenitor cells, endothelial progenitor cells, vascular endothelial cells, embryonic fibroblasts, and some cells in fetal and adult nervous tissue. The antigen is absent on fully differentiated hematopoietic cells, such as normal peripheral blood lymphocytes, monocytes, granulocytes, erythrocytes, and platelets. Clone AC136 has a similar specificity as the CD34 monoclonal antibody clone 8G12 (HPCA-2). CD34 antibodies can be used for studies of hematopoiesis and nonhematopoietic stem cells, phenotyping of hematopoietic stem cells, and studies on phenotyping of hematologic malignancies, endothelial cells, and endothelial progenitor cells (EPCs).