title: Altered Ig levels and antibody responses in mice deficient for the Fc receptor for IgM (FcμR).
abstract: Cell surface Fc receptor for IgM antibody (FcμR) is the most recently identified member among FcRs. We determined the cellular distribution of mouse FcμR and the functional consequences of Fcmr disruption. Surface FcμR expression was restricted to B-lineage cells, from immature B to plasma cells, except for a transient down-modulation during germinal center reactions. Fcmr ablation had no significant effect on overall B- and T-cell development, but led to a reduction of marginal zone B cells and an increase in splenic B1 B cells. Preimmune serum IgM in mutant mice was significantly elevated as were natural autoantibodies. When immunized with live attenuated pneumococci, mutant mice mounted robust antibody responses against phosphorylcholine, but not protein, determinants compared with wild-type mice. By contrast, upon immunization with a hapten-carrier conjugate, nitrophenyl-coupled chicken γ-globulin (NP-CGG), the mutant mice had a diminished primary IgG1 response to both NP and CGG. These findings suggest that FcμR has an important role in IgM homeostasis and regulation of humoral immune responses.
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Honjo
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kubagawa
authors.forename: Dewitt M
authors.initials: DM
authors.lastname: Jones
authors.forename: Brian
authors.initials: B
authors.lastname: Dizon
authors.forename: Zilu
authors.initials: Z
authors.lastname: Zhu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohno
authors.forename: Shozo
authors.initials: S
authors.lastname: Izui
authors.forename: John F
authors.initials: JF
authors.lastname: Kearney
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kubagawa
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology*; D006706:Homeostasis / Q000502:physiology; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology*; D007075:Immunoglobulin M / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology*; D011961:Receptors, Fc / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011961:Receptors, Fc