Murine hematopoietic progenitor cells with colony-forming or radioprotective capacity lack expression of the beta 2-integrin LFA-1.
Recently, we have demonstrated that antibodies that block the function of the beta2-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 <.001). We found that the radioprotective capacity resided almost exclusively in the LFA-1(neg) cell fraction, the radioprotection rate after transplantation of 10(3), 3 x 10(3), 10(4), and 3 x 10(4) cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1(pos) cells. Similarly, in cytokine (IL-8 and G-CSF)-mobilized blood, the LFA-1(neg) fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)-/Rhodamine (Rho)- sorted cells, were examined. More than 95% of the Rho- cells were LFA-1(neg). Cultures of sorted cells showed that the LFA-1(neg) fraction contained all CFU. Transplantation of 150 Rho- LFA-1(neg) or up to 600 Rho-LFA-1(pos) cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.
Pruijt
J F
JF
Laboratory of Experimental Hematology, Department of Hematology, Leiden University Medical Center, Leiden, The Netherlands.
van Kooyk
Y
Y
Figdor
C G
CG
Willemze
R
R
Fibbe
W E
WE
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism / Q000528:radiation effects; D018821:CD18 Antigens / Q000096:biosynthesis* / Q000528:radiation effects; D002454:Cell Differentiation / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002469:Cell Separation; D002470:Cell Survival / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D016207:Cytokines / Q000097:blood / Q000528:radiation effects; D005260:Female; D005720:Gamma Rays; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000528:radiation effects*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000096:biosynthesis* / Q000528:radiation effects; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D014916:Whole-Body Irradiation
D018821:CD18 Antigens; D016207:Cytokines; D016169:Lymphocyte Function-Associated Antigen-1