title: Naive recirculating B cells mature simultaneously in the spleen and bone marrow.
abstract: We have recently demonstrated that IgD(hi) B cells can occupy an extravascular perisinusoidal niche in the bone marrow in addition to the well-established follicular niche in conventional secondary lymphoid organs. The spleen has long been considered to be the site at which newly formed B lymphocytes mature into IgD(hi) naive recirculating B cells, but the existence of mutant mice that have selectively lost mature B cells in the bone marrow prompted an examination of B-cell maturation at this latter site. Following a single pulse of BrdU in intact mice, sequential labeling of more mature B-cell populations in the bone marrow suggested ongoing maturation at this site. Further evidence for B-cell maturation in the bone marrow was obtained from analyses of transitional B cells in splenectomized lymphotoxin alpha-deficient mice that lack all secondary lymphoid organs. In these mice, antibody-secreting cells recognizing multivalent antigens were also observed in the bone marrow following an intravenous microbial challenge. These data suggest that newly formed B cells mature into IgD(hi) B cells simultaneously in the spleen and the bone marrow and establish in a stringent manner that humoral immune responses can be initiated in situ in the bone marrow.
authors.affiliation: Massachusetts General Hospital and Harvard Medical School, Boston, MA 02129, USA.
authors.forename: Annaiah
authors.initials: A
authors.lastname: Cariappa
authors.forename: Catharine
authors.initials: C
authors.lastname: Chase
authors.forename: Haoyuan
authors.initials: H
authors.lastname: Liu
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
authors.forename: Shiv
authors.initials: S
authors.lastname: Pillai
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D001854:Bone Marrow Cells / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D002454:Cell Differentiation; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000276:immunology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D008233:Lymphotoxin-alpha / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D013154:Spleen / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D013156:Splenectomy
chemical_list: D000941:Antigens; D007075:Immunoglobulin M; D008233:Lymphotoxin-alpha