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Administration of GM-CSF after autologous hemopoietic stem cell transplantation in patients with lymphoma resulted in accelerated myeloid recovery, particularly in patients who received peripheral blood stem cells and nonpurged bone marrow, and was associated with a decreased incidence of bacterial infections.

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We explored the expression of a lymphocyte homing-associated cell adhesion molecule (H-CAM, CD44) on hematopoietic progenitors. We demonstrate that immature myeloid and erythroid leukemic cell lines stain intensely with monoclonal antibodies Hermes-1 and Hermes-3, which define distinct epitopes on lymphocyte surface H-CAM, a glycoprotein involved in lymphocyte interactions with endothelial cells. Using fluorescence-activated cell sorting (FACS), human marrow cells were fractionated into Hermeshi, Hermesmed, and Hermeslo populations according to the expression of both the Hermes-1 and Hermes-3 epitopes. Granulocyte-macrophage colony-forming unit and erythroid burst-forming unit precursors were found predominantly in the brightly positive fractions. Two-color FACS analysis confirmed that the My10 (CD34) positive populations of cells in bone marrow, which contain most of the progenitor cell activity, are brightly positive for Hermes-1. Finally, we demonstrate that among bone marrow cells, the highest levels of H- CAM are expressed on myeloid and erythroid progenitors as well as mature granulocytes and lymphocytes. Thus we provide evidence that molecules related or identical to the H-CAM homing receptor are expressed on marrow progenitor cells. H-CAM may contribute to progenitor cell interactions with marrow endothelial and stromal cell elements important to the maintenance and regulation of hematopoiesis.

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