title: Enhancement of G-CSF-induced stem cell mobilization by antibodies against the beta 2 integrins LFA-1 and Mac-1.
abstract: The beta 2 integrins leukocyte function antigen-1 (LFA-1, CD11a) and macrophage antigen-1 (Mac-1, CD11b) have been reported to play a role in the attachment of CD34(+) cells to stromal cells in the bone marrow. When administered prior to interleukin-8 (IL-8), anti-LFA-1 antibodies completely prevent the IL-8-induced mobilization of hematopoietic stem cells in mice. Here, we studied the role of anti-beta 2 integrin antibodies in granulocyte colony-stimulating factor (G-CSF)-induced mobilization of hematopoietic progenitor cells. Administration of antibodies against the alpha chain of LFA-1 or against the alpha chain of Mac-1 followed by daily injections of G-CSF for more than 1 day resulted in a significant enhancement of mobilization of hematopoietic progenitor cells when compared with mobilization induced by G-CSF alone. Also, the number of late (day 28) cobblestone area-forming cells in vitro was significantly higher after mobilization with anti-LFA-1 antibodies followed by 5 microg G-CSF for 5 days than with G-CSF alone (119 +/- 34 days vs 17 +/- 14 days), indicating mobilization of repopulating stem cells. Pretreatment with blocking antibodies to intercellular adhesion molecule-1 (ICAM-1; CD54), a ligand of LFA-1 and Mac-1, did not result in an effect on G-CSF-induced mobilization, suggesting that the enhancing effect required an interaction of the beta 2 integrins and one of their other ligands. Enhancement of mobilization was not observed in LFA-1-deficient (CD11a) mice, indicating that activated cells expressing LFA-1 mediate the synergistic effect, rather than LFA-1-mediated adhesion.
authors.affiliation: Laboratory of Experimental Hematology, Department of Hematology, Leiden University Medical Center, The Netherlands.
authors.forename: Gerjo A
authors.initials: GA
authors.lastname: Velders
authors.forename: Johannes F M
authors.initials: JF
authors.lastname: Pruijt
authors.forename: Perry
authors.initials: P
authors.lastname: Verzaal
authors.forename: Ronald
authors.initials: R
authors.lastname: van Os
authors.forename: Yvette
authors.initials: Y
authors.lastname: van Kooyk
authors.forename: Carl G
authors.initials: CG
authors.lastname: Figdor
authors.forename: Evert-Jan F M
authors.initials: EJ
authors.lastname: de Kruijf
authors.forename: Roel
authors.initials: R
authors.lastname: Willemze
authors.forename: Willem E
authors.initials: WE
authors.lastname: Fibbe
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D001773:Blood Cells / Q000166:cytology / Q000187:drug effects; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects; D018821:CD18 Antigens / Q000276:immunology; D003114:Colony-Forming Units Assay; D004357:Drug Synergism; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D016169:Lymphocyte Function-Associated Antigen-1 / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout
chemical_list: D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D016179:Granulocyte Colony-Stimulating Factor