title: Pivotal advance: characterization of mouse liver phagocytic B cells in innate immunity.
abstract: Although B cells in vertebrates have been thought to lack phagocytic activity, there has been a recent report of such ability by the B cells of early vertebrates such as fish and frogs. Here, we show for the first time that mouse liver IgM(+) B cells actively phagocytose microsphere beads and Escherichia coli and that they effectively kill bacterial cells. Such phagocytic activity is not observed in other liver MNCs, except for F4/80(+) Kupffer cells. In the presence of fresh mouse serum (but not heat-inactivated serum), the heat-killed E. coli phagocytic activity of liver B cells increased significantly but was inhibited significantly by anticomplement component C3 antibody, suggesting E. coli opsonization by serum factors, including complement components. Upon i.v. injection of FITC-labeled E. coli into mice, a substantial proportion of liver B cells phagocytosed the bacteria, as compared with spleen B cells. Functional phagolysosome formation in liver B cells was supported by several reagents showing an acidic change and lysosomes in the phagocytosed vacuoles. Indeed, mouse liver B cells killed viable E. coli more efficiently than did spleen B cells in vitro. Further, E. coli-phagocytic liver B cells produced a substantial amount of IL-12. These results indicate that liver B cells have phagocytic and bactericidal activities similar to those of dedicated phagocytes and may contribute to bacterial clearance.
authors: Department of Immunology and Microbiology, National Defense Medical College, Tokorozawa, Japan.
authors: Masahiro
authors: M
authors: Nakashima
authors: Manabu
authors: M
authors: Kinoshita
authors: Hiroyuki
authors: H
authors: Nakashima
authors: Yoshiko
authors: Y
authors: Habu
authors: Hiromi
authors: H
authors: Miyazaki
authors: Satoshi
authors: S
authors: Shono
authors: Sadayuki
authors: S
authors: Hiroi
authors: Nariyoshi
authors: N
authors: Shinomiya
authors: Kuniaki
authors: K
authors: Nakanishi
authors: Shuhji
authors: S
authors: Seki
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D003165:Complement System Proteins / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology; D007113:Immunity, Innate / Q000502:physiology*; D007075:Immunoglobulin M / Q000276:immunology; D018664:Interleukin-12 / Q000276:immunology*; D008099:Liver / Q000166:cytology / Q000276:immunology*; D051379:Mice; D008863:Microspheres; D010587:Phagocytosis / Q000502:physiology*
chemical_list: D007075:Immunoglobulin M; D018664:Interleukin-12; D003165:Complement System Proteins