title: CCR5-binding chemokines modulate CXCL12 (SDF-1)-induced responses of progenitor B cells in human bone marrow through heterologous desensitization of the CXCR4 chemokine receptor.
abstract: Although the SDF-1 (CXCL12)/CXCR4 axis is important for B-cell development, it is not yet clear to what extent CC chemokines might influence B lymphopoiesis. In the current study, we characterized CC chemokine receptor 5 (CCR5) expression and function of primary progenitor B-cell populations in human bone marrow. CCR5 was expressed on all bone marrow B cells at levels between 150 and 200 molecules per cell. Stimulation of bone marrow B cells with the CCR5-binding chemokine macrophage inflammatory protein 1beta (MIP-1beta; CCL4) did not cause chemotaxis, but CCL4 was able to trigger potent calcium mobilization responses and activation of the mitogen-activated protein kinase (MAPK) pathway in developing B cells. We also determined that CCR5-binding chemokines MIP-1alpha (CCL3), CCL4, and RANTES (CCL5), specifically by signaling through CCR5, could affect all progenitor B-cell populations through a novel mechanism involving heterologous desensitization of CXCR4. This cross-desensitization of CXCR4 was manifested by the inhibition of CXCL12-induced calcium mobilization, MAPK activation, and chemotaxis. These findings indicate that CCR5 can indeed mediate biologic responses of bone marrow B cells, even though these cell populations express low levels of CCR5 on their cell surface. Thus, by modulation of CXCR4 function, signaling through CCR5 may influence B lymphopoiesis by affecting the migration and maturation of B-cell progenitors in the bone marrow microenvironment.
authors.affiliation: Joint Program in Transfusion Medicine, Harvard Medical School, Children's Hospital Boston, MA, USA.
authors.forename: Marek
authors.initials: M
authors.lastname: Honczarenko
authors.forename: Yi
authors.initials: Y
authors.lastname: Le
authors.forename: Aleksandra M
authors.initials: AM
authors.lastname: Glodek
authors.forename: Marcin
authors.initials: M
authors.lastname: Majka
authors.forename: James J
authors.initials: JJ
authors.lastname: Campbell
authors.forename: Mariusz Z
authors.initials: MZ
authors.lastname: Ratajczak
authors.forename: Leslie E
authors.initials: LE
authors.lastname: Silberstein
mesh_terms: D000328:Adult; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000276:immunology* / Q000502:physiology; D002633:Chemotaxis / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology*; D006801:Humans; D019713:Receptors, CCR5 / Q000235:genetics / Q000276:immunology*; D019718:Receptors, CXCR4 / Q000276:immunology*; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D019713:Receptors, CCR5; D019718:Receptors, CXCR4