Murine hematopoietic progenitor cells with colony-forming or radioprotective capacity lack expression of the β2-integrin LFA-1

Abstract

Recently, we have demonstrated that antibodies that block the function of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1-mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow ± 50% of the mononuclear cells (MNC) were LFA-1(neg). Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G- CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL- 6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA- 1(neg) fraction contained the majority of the colony-forming cells (CFCs) (LFA-1(neg) 183 ± 62/7,500 cells v LFA-1(pos) 29 ± 17/7,500 cells, P