title: CD44 Antibody Inhibition of Macrophage Phagocytosis Targets Fcγ Receptor- and Complement Receptor 3-Dependent Mechanisms.
abstract: Targeting CD44, a major leukocyte adhesion molecule, using specific Abs has been shown beneficial in several models of autoimmune and inflammatory diseases. The mechanisms contributing to the anti-inflammatory effects of CD44 Abs, however, remain poorly understood. Phagocytosis is a key component of immune system function and can play a pivotal role in autoimmune states where CD44 Abs have shown to be effective. In this study, we show that the well-known anti-inflammatory CD44 Ab IM7 can inhibit murine macrophage phagocytosis of RBCs. We assessed three selected macrophage phagocytic receptor systems: Fcγ receptors (FcγRs), complement receptor 3 (CR3), and dectin-1. Treatment of macrophages with IM7 resulted in significant inhibition of FcγR-mediated phagocytosis of IgG-opsonized RBCs. The inhibition of FcγR-mediated phagocytosis was at an early stage in the phagocytic process involving both inhibition of the binding of the target RBC to the macrophages and postbinding events. This CD44 Ab also inhibited CR3-mediated phagocytosis of C3bi-opsonized RBCs, but it did not affect the phagocytosis of zymosan particles, known to be mediated by the C-type lectin dectin-1. Other CD44 Abs known to have less broad anti-inflammatory activity, including KM114, KM81, and KM201, did not inhibit FcγR-mediated phagocytosis of RBCs. Taken together, these findings demonstrate selective inhibition of FcγR and CR3-mediated phagocytosis by IM7 and suggest that this broadly anti-inflammatory CD44 Ab inhibits these selected macrophage phagocytic pathways. The understanding of the immune-regulatory effects of CD44 Abs is important in the development and optimization of therapeutic strategies for the potential treatment of autoimmune conditions.
authors.affiliation: Canadian Blood Services Centre for Innovation, Toronto, Ontario K1G 4J5, Canada; Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5B 1T8, Canada;
authors.forename: Alaa
authors.initials: A
authors.lastname: Amash
authors.affiliation: Department of Hematology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China;
authors.forename: Lin
authors.identifier: http://orcid.org/0000-0001-8922-8826
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Hematology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China;
authors.forename: Yawen
authors.identifier: http://orcid.org/0000-0003-4876-1207
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; and.
authors.forename: Varsha
authors.initials: V
authors.lastname: Bhakta
authors.affiliation: Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5B 1T8, Canada;
authors.forename: Gregory D
authors.identifier: http://orcid.org/0000-0001-6508-168X
authors.initials: GD
authors.lastname: Fairn
authors.affiliation: Department of Hematology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China;
authors.forename: Ming
authors.initials: M
authors.lastname: Hou
authors.affiliation: Department of Hematology, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China;
authors.forename: Jun
authors.initials: J
authors.lastname: Peng
authors.affiliation: Canadian Blood Services Centre for Innovation, Toronto, Ontario K1G 4J5, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; and.
authors.forename: William P
authors.identifier: http://orcid.org/0000-0002-5870-8189
authors.initials: WP
authors.lastname: Sheffield
authors.affiliation: Canadian Blood Services Centre for Innovation, Toronto, Ontario K1G 4J5, Canada; Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario M5B 1T8, Canada; Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A1, Canada lazarusa@smh.ca.
authors.forename: Alan H
authors.initials: AH
authors.lastname: Lazarus
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000276:immunology / Q000494:pharmacology; D019138:Antibodies, Blocking / Q000276:immunology / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D002460:Cell Line; D004912:Erythrocytes / Q000276:immunology; D018960:Hyaluronan Receptors / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D007249:Inflammation / Q000276:immunology / Q000517:prevention & control; D037181:Lectins, C-Type / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000276:immunology*; D011951:Receptors, Complement / Q000276:immunology*; D017452:Receptors, IgG / Q000276:immunology*; D015054:Zymosan / Q000276:immunology; D000099181:Dectin-1
chemical_list: D000893:Anti-Inflammatory Agents; D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D018960:Hyaluronan Receptors; D007074:Immunoglobulin G; D037181:Lectins, C-Type; D011951:Receptors, Complement; D017452:Receptors, IgG; D015054:Zymosan; D000099181:Dectin-1; C476399:Cd44 protein, mouse