title: Survival of residual neutrophils and accelerated myelopoiesis limit the efficacy of antibody-mediated depletion of Ly-6G+ cells in tumor-bearing mice.
abstract: Expansion of Ly-6G(+) myeloid cells has been reported in most murine cancer models. However, divergent findings exist regarding the role and effect of these cells on host immunity and tumor progression. Antibody-mediated depletion of Ly-6G(+) cells is a common technique to assess the in vivo relevance of these cells. Interpretation of results crucially depends on the efficacy and course of depletion. We established murine head and neck cancer models and analyzed the efficacy of antibody-mediated depletion by flow cytometry, conventional histology, and intravital imaging with a novel Ly-6G-transgenic mouse model. The first phase of depletion was characterized by effective elimination of Ly-6G(+) cells from the peripheral blood. Nevertheless, viable, resistant cells were found to reside in the tumor tissue and spleen. This peripheral depletion phase was associated with high systemic levels of granulocyte colony-stimulating factor and KC and enhanced splenic production of Ly-6G(+) cells. Even under sustained treatment with either αGr-1 or αLy-6G antibodies, peripheral blood depletion ended after approximately 1 wk and was followed by reappearance of immature Ly-6G(+) cells with an immunoregulatory phenotype. Reappearance of these depletion-resistant immature cells was enhanced in tumor-bearing, compared with naïve, control mice. Collectively, our data suggest that depletion of Ly-6G(+) myeloid cells in tumor-bearing mice is counteracted by the persistence of intratumoral cells, enhanced extramedullary granulopoiesis, and accelerated reappearance of immature cells. Hence, extensive monitoring of in vivo kinetics and tissue distribution of Ly-6G(+) cells is required in depletion studies.
authors.affiliation: Department of Otorhinolaryngology, University Hospital Essen, University Duisburg-Essen, Essen, Germany; and.
authors.forename: Katrin
authors.initials: K
authors.lastname: Moses
authors.affiliation: Department of Otorhinolaryngology, University Hospital Essen, University Duisburg-Essen, Essen, Germany; and.
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Klein
authors.affiliation: Institute for Experimental Immunology and Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Männ
authors.affiliation: Institute for Experimental Immunology and Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
authors.forename: Anika
authors.initials: A
authors.lastname: Klingberg
authors.affiliation: Institute for Experimental Immunology and Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Gunzer
authors.affiliation: Department of Otorhinolaryngology, University Hospital Essen, University Duisburg-Essen, Essen, Germany; and sven.brandau@uk-essen.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Brandau
mesh_terms: D000818:Animals; D000906:Antibodies / Q000378:metabolism*; D000950:Antigens, Ly / Q000378:metabolism*; D039481:CD11b Antigen / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002470:Cell Survival; D018925:Chemokines / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000473:pathology*; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D038042:Myelopoiesis; D009504:Neutrophils / Q000473:pathology*; D013154:Spleen / Q000473:pathology
chemical_list: D000906:Antibodies; D000950:Antigens, Ly; D039481:CD11b Antigen; D018925:Chemokines; C480309:Ly6G antigen, mouse
keywords: Gr-1 depletion; MDSC; extramedullary granulopoiesis; head and neck cancer; tumor-associated neutrophils