title: Novel B cell population producing functional IgG in the absence of membrane IgM expression.
abstract: Surface expression of IgM is a characteristic feature of the development of most B cells. Only pre-B cells bearing functional IgM heavy chains mu chains) are selected for clonal expansion and differentiation. Cells lacking mu chains are normally eliminated. muMT mice carrying a deletion of the first exon coding for the transmembrane domain of the immunoglobulin mu chain gene were described as mice deficient for mature B cells, plasma cells and immunoglobulins in serum. In this study, we describe in muMT/BALB/c mice the presence of a novel B cell population, producing IgG, IgA and IgE in the absence of IgM membrane expression. Moreover, this small population of B cells is able to recognize antigens and to differentiate into plasma cells. These "non-conventional" mu(- / -) B cells produce functional immunoglobulins after immunization, undergo germinal center reactions, and maintain B cell memory. Our findings support the concept, that a small percentage of mu -non-expressing pre-B cells can escape elimination, switch to downstream immunoglobulin heavy chains and respond to antigens. It remains an open question how the reactivity of these B cells is regulated and in which extent such B cells play a role in physiological and pathological processes such as autoantibody production and autoimmunity.
authors.affiliation: Department of Immunology and Cell Biology, Research Center Borstel, Borstel, Germany.
authors.forename: Zane
authors.initials: Z
authors.lastname: Orinska
authors.forename: Anna
authors.initials: A
authors.lastname: Osiak
authors.forename: Jürgen
authors.initials: J
authors.lastname: Löhler
authors.forename: Elena
authors.initials: E
authors.lastname: Bulanova
authors.forename: Vadim
authors.initials: V
authors.lastname: Budagian
authors.forename: Ivan
authors.initials: I
authors.lastname: Horak
authors.forename: Silvia
authors.initials: S
authors.lastname: Bulfone-Paus
mesh_terms: D000818:Animals; D000941:Antigens / Q000008:administration & dosage; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation; D005803:Genes, Immunoglobulin; D018858:Germinal Center / Q000166:cytology / Q000276:immunology; D018928:Immunity, Mucosal; D007114:Immunization; D007070:Immunoglobulin A / Q000097:blood; D007072:Immunoglobulin D / Q000378:metabolism; D007073:Immunoglobulin E / Q000097:blood; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000097:blood; D007075:Immunoglobulin M / Q000172:deficiency* / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D008221:Lymphoid Tissue / Q000166:cytology / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008817:Mice, Mutant Strains; D009154:Mutation; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*
chemical_list: D000941:Antigens; D007070:Immunoglobulin A; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains; D011947:Receptors, Antigen, B-Cell; D007073:Immunoglobulin E