ABSTRACT

I. HUMAN HEMATOPOIETIC CD34+ CELLS The human CD34 cell-surface antigen (Ag) is a highly glycosylated 115 kDa type I integral membrane protein expressed in only 1-4% of normal adult bone marrow mononuclear cells (1). All hematopoietic progenitor cells including the early multipotential long-term culture initiating cells (LTC-IC), blast colony-forming cell (Bl-CFC), mixed colony-forming cell (MIX-CFC), granulocyte-macrophage colony-forming cell (GM-CFC), erythroid blast-forming cell (E-BFC), and megakaryocytic colony-forming cell (Meg-CFC) are CD34+ (2). As the hematopoietic progenitor cells differentiate and become committed to particular lineages, CD34 expression is progressively reduced and all precursor and mature hematopoietic cells are CD34-(3).