Characterization of CD34+ Human Hemopoietic Progenitor Cells from the Peripheral Blood: Enzyme-, Carbohydrate- and Immunocytochemistry, Morphometry, and Ultrastructure

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Abstract
Following an immunomagnetic isolation and enrichment procedure, CD34+ cells were harvested from the peripheral blood of about 50 healthy donors. A battery of cytochemical staining reactions, monoclonal and carbohydrate-specific antibodies, proliferation markers and lectins was applied on smears and sections from paraffin-embedded pellets. Additionally, a morphometric analysis and ultrastruc-tural investigation was carried out. More than 95% of the total yield of progenitor cells expressed CD34 and CD43 (MT1) and of these about 90% CD45 (LCA) and 25% CD45RA (MT2). The CD34VCD45RA population was thought to represent very primitive, probably not lineage-restricted stem cells. On the other hand, reactivity with ANAE, CD11c, CD15, CD20, Ret40f, KiMlP, and CD61 (ranging between 1 to 20%) was considered to indicate a transition into more differentiated elements of hemopoiesis. The failure to detect any staining with proliferation markers (Ki-67/MIBl, PCNA, KiS1) was in keeping with a quiescent status. Carbohydrate antigens revealed a pattern which underlines the fact that the CD34 and CD43 antigens belong to the family of heavily O-glycosylated sialomucins. Blood group antigens which are located at the peripheral regions of mucin-oligosaccharides (H type 2, Lewisx, Lewisa) could be demonstrated, but no t. A, B, Sialyl-Lewisx and Lewisy. Morphometric analysis revealed that CD34+ progenitors were larger than small lymphocytes. Electron microscopy showed a relatively primitive cytoplasmic organization and numerous tiny magnetic beads clustered at the plasma membrane.