title: M2 macrophages phagocytose rituximab-opsonized leukemic targets more efficiently than m1 cells in vitro.
abstract: Because macrophages have been implicated as major players in the mechanism of action of rituximab, we have investigated the factors that modulate their tumor cell killing potential. Human macrophages, differentiated in vitro from peripheral blood monocytes, were used in binding and phagocytosis assays using B-chronic lymphocytic leukemia or lymphoma target cells opsonized with rituximab. Phagocytosis was maximal at 0.1 microg/ml rituximab and was not significantly affected by CD20 expression levels or by CD16A polymorphism at position 158 (Val/Phe). The role of FcgammaRs was demonstrated by complete inhibition of phagocytosis by excess human Igs. Because macrophages can be differentiated to M1- or M2-type cells with either GM-CSF or M-CSF, respectively, and can be classically activated by proinflammatory stimuli (IFN-gamma/LPS) or undergo alternative activation with cytokines such as IL-4 or IL-10, we have analyzed the effect of these different polarization programs on the phagocytosis mediated by rituximab. Macrophages differentiated in presence of M-CSF showed a 2- to 3-fold greater phagocytic capacity compared with GM-CSF-induced cells. Furthermore, addition of IL-10 significantly increased, whereas IL-4 decreased phagocytosis by both M-CSF- and GM-CSF-differentiated macrophages. LPS/IFN-gamma had little effect. Expression of CD16, CD32, and CD64 in different macrophage populations correlated with phagocytic activity. Interestingly, several B lymphoma cell lines were observed to secrete 400-1300 pg/ml IL-10 in vitro, and coculture of human macrophages with lymphoma conditioned medium increased significantly their phagocytic capacity. Our data suggest that cytokines secreted by lymphoma cells can favor alternate activation of macrophages with a high phagocytic capacity toward rituximab-opsonized targets.
authors.affiliation: Ospedali Riuniti di Bergamo, Italy.
authors.forename: Marzia
authors.initials: M
authors.lastname: Leidi
authors.forename: Elisa
authors.initials: E
authors.lastname: Gotti
authors.forename: Luca
authors.initials: L
authors.lastname: Bologna
authors.forename: Elena
authors.initials: E
authors.lastname: Miranda
authors.forename: Monica
authors.initials: M
authors.lastname: Rimoldi
authors.forename: Antonio
authors.initials: A
authors.lastname: Sica
authors.forename: Massimo
authors.initials: M
authors.lastname: Roncalli
authors.forename: Giuseppe A
authors.initials: GA
authors.lastname: Palumbo
authors.forename: Martino
authors.initials: M
authors.lastname: Introna
authors.forename: Josée
authors.initials: J
authors.lastname: Golay
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000494:pharmacology; D058846:Antibodies, Monoclonal, Murine-Derived; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D000970:Antineoplastic Agents / Q000276:immunology / Q000494:pharmacology; D015153:Blotting, Western; D002454:Cell Differentiation / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006801:Humans; D066298:In Vitro Techniques; D008232:Lymphoproliferative Disorders / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology; D016173:Macrophage Colony-Stimulating Factor; D008264:Macrophages / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D009895:Opsonin Proteins / Q000276:immunology* / Q000494:pharmacology; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology*; D011110:Polymorphism, Genetic; D017452:Receptors, IgG / Q000276:immunology; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D015703:Antigens, CD; D000970:Antineoplastic Agents; D016207:Cytokines; D009895:Opsonin Proteins; D017452:Receptors, IgG; D000069283:Rituximab; D016173:Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor