title: B-1-cell subpopulations contribute differently to gut immunity.
abstract: In mice, B-1 (B1a/B1b) cells are mainly located in the peritoneal cavity. B-1 cells are well known for their role in the early stages of Ab-mediated immune responses against pathogenic invasion as well as for the production of natural IgM antibodies. Although such B cells have been claimed to give rise to intestinal plasma cells producing IgA, a clear role of B-1 cells in IgA production in the gut-associated tissues is still not defined. Here, we employed the transgenic L2 mouse model characterized by the lack of B-2 cells and presence of B-1 cells as major B-cell subpopulation. The oligoclonality of the Ab repertoire in this mouse allowed us to take typical B1a cell VH sequences as indicators of the presence of IgM-producing B-1a cells in Peyer's patches as well as in lamina propria. However, amongst the IgAVH sequences recovered from the same tissues, none of the sequences showed B1a-cell specificity. Interestingly, all IgAVH sequences derived from the lamina propria of L2 mice displayed extensive numbers of nucleotide exchanges, indicating somatic hypermutation, and affinity maturation. This suggests that the contribution of natural unmutated IgA by B-1a cells to intestinal immunity is negligible.
authors.affiliation: Molecular Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany. Bishnudeo.Roy@helmholtz-hzi.de
authors.forename: Bishnudeo
authors.initials: B
authors.lastname: Roy
authors.forename: Shiwani
authors.initials: S
authors.lastname: Agarwal
authors.forename: Anne-Margarete
authors.initials: AM
authors.lastname: Brennecke
authors.forename: Martina
authors.initials: M
authors.lastname: Krey
authors.forename: Oliver
authors.initials: O
authors.lastname: Pabst
authors.forename: Sandra
authors.initials: S
authors.lastname: Düber
authors.forename: Siegfried
authors.initials: S
authors.lastname: Weiss
mesh_terms: D000818:Animals; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D007070:Immunoglobulin A / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D017578:Immunoglobulin Class Switching; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology*; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology*; D007413:Intestinal Mucosa / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009092:Mucous Membrane / Q000276:immunology; D010529:Peritoneal Cavity; D010581:Peyer's Patches / Q000276:immunology; D027041:Somatic Hypermutation, Immunoglobulin
chemical_list: D007070:Immunoglobulin A; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region
keywords: B-1 cells; Class switching; Gut immunity; IgA; Somatic hypermutation