title: Murine complement receptor 1 is required for germinal center B cell maintenance but not initiation.
abstract: Germinal centers are the anatomic sites for the generation of high affinity immunoglobulin expressing plasma cells and memory B cells. The germinal center B cells that are precursors of these cells circulate between the light zone B cell population that interact with antigen laden follicular dendritic cells (FDC) and the proliferative dark zone B cell population. Antigen retention by follicular dendritic cells is dependent on Fc receptors and complement receptors, and complement receptor 1 (Cr1) is the predominant complement receptor expressed by FDC. The newly created Cr1KO mouse was used to test the effect of Cr1-deficiency on the kinetics of the germinal center reaction and the generation of IgM and switched memory B cell formation. Immunization of Cr1KO mice with a T cell-dependent antigen resulted in the normal initial expansion of B cells with a germinal center phenotype however these cells were preferentially lost in the Cr1KO animal over time (days). Bone marrow chimera animals documented the surprising finding that the loss of germinal center B cell maintenance was linked to the expression of Cr1 on B cells, not the FDC. Cr1-deficiency further resulted in antigen-specific IgM titer and IgM memory B cell reductions, but not antigen-specific IgG after 35-37 days. Investigations of nitrophenyl (NP)-specific IgG demonstrated that Cr1 is not necessary for affinity maturation during the response to particulate antigen. These data, along with those generated in our initial description of the Cr1KO animal describe unique functions of Cr1 on the surface of both B cells and FDC.
authors.affiliation: Division of Microbiology and Immunology, Department of Pathology, The University of Utah School of Medicine, Salt Lake City, UT 84112, United States.
authors.forename: Luke R
authors.initials: LR
authors.lastname: Donius
authors.affiliation: Division of Microbiology and Immunology, Department of Pathology, The University of Utah School of Medicine, Salt Lake City, UT 84112, United States.
authors.forename: Janis J
authors.initials: JJ
authors.lastname: Weis
authors.affiliation: Division of Microbiology and Immunology, Department of Pathology, The University of Utah School of Medicine, Salt Lake City, UT 84112, United States. Electronic address: john.weis@path.utah.edu.
authors.forename: John H
authors.initials: JH
authors.lastname: Weis
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001854:Bone Marrow Cells / Q000276:immunology; D049109:Cell Proliferation; D002678:Chimera / Q000276:immunology; D020566:Dendritic Cells, Follicular / Q000276:immunology*; D018858:Germinal Center / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology*; D007156:Immunologic Memory; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009596:Nitrophenols / Q000276:immunology; D017463:Receptors, Complement 3b / Q000235:genetics*; D011961:Receptors, Fc / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D009596:Nitrophenols; D017463:Receptors, Complement 3b; D011961:Receptors, Fc
keywords: Adaptive immunity; B cell; Complement receptor