IL-2 Receptor γChain Expression on CD34 Positive Hematopoietic Progenitor Cells from Bone Marrow and Cord Blood

Abstract

The IL-2 receptor (IL-2R) γchain is shared among receptors for IL-4, IL-7, IL-9 and IL-15 as well as IL-2. In order to clarify the functional role of these cytokines interacting with the common γchain in human early hematopoiesis, we studied expression of the IL-2R γchain on purified CD34 positive cells from bone marrow and cord blood. Broad populations of bone marrow mononuclear cells were all found to express the IL-2R γchain. CD34 positive cells were purified by CD34 monoclonal antibodies and immunomagnetic beads as representative hematopoietic progenitor cells. It was established that only 38±10% of CD34 positive bone marrow cells (n = 5) and 35±12% of CD34 positive cord blood cells (n =11) expressed the IL-2R γchain. CD34(+) IL-2R γchain(+) and CD34(+) IL-2R γchain(−) cells fractionated by cell sorting were subjected to clonogenic assays that showed granulocyte-macrophage colony-forming cells (CFU-GM) were present evenly in both fractions, whereas erythroid burst-forming cells (BFU-E) were enriched in the CD34(+) IL-2R γchain( fraction approximately two- to six-fold as compared with CD34(+) IL-2R γchain(+) fraction. Such clonogenic features did not differ between the bone marrow and cord blood cases. These results indicate that CD34(+) IL-2R γchain(−) cells contain immature cells already committed to the erythroid lineage.