Commitment to erythroid or granulocyte-macrophage differentiation is associated with loss of macromolecular insoluble cold globulin.

In mice a macromolecular insoluble cold globulin (MICG) is present on the surface of resting and stimulated peripheral T lymphocytes, thymocytes, fetal prothymocytes and hemopoietic stem cells forming spleen colonies, colony-forming unit-spleen (CFU-S). Here we demonstrate that removal of MICG positive cells from bone marrow by treatment with antibody and complement does not affect the number of erythroid, burst-forming unit-erythroid (BFU-E) and granulocyte-macrophage, colony-forming unit-granulocyte macrophage (CFU-GM) progenitors developing in vitro. Thus, commitment of stem cells to lineage specific differentiation is associated with the loss of the MICG marker. Furthermore, the removal of MICG positive T lymphocytes from bone marrow does not affect the growth of BFU-E or CFU-GM.