IL-2 receptor gamma chain expression on CD34 positive hematopoietic progenitor cells from bone marrow and cord blood

The IL-2 receptor (IL-BR) gamma chain 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 gamma chain in human early hematopoiesis, we studied expression of the IL-2R gamma chain 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 gamma chain. 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 gamma chain. CD34(+) IL-2R gamma chain(+) and CD34(+) IL-2R gamma chain(-) 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 gamma chain(-) fraction approximately two- to six-fold as compared with CD34(+) IL-BR gamma chain(+) fraction. Such clonogenic features did not differ between the bone marrow and cord blood cases. These results indicate that CD34(+) IL-2R gamma chain(-) cells contain immature cells already committed to the erythroid lineage.