Novel B cell population producing functional IgG in the absence of membrane IgM expression

Eur J Immunol. 2002 Dec;32(12):3472-80. doi: 10.1002/1521-4141(200212)32:12<3472::AID-IMMU3472>3.0.CO;2-F.


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.

MeSH terms

  • Animals
  • Antigens / administration & dosage
  • B-Lymphocyte Subsets / cytology
  • B-Lymphocyte Subsets / immunology*
  • Cell Differentiation
  • Genes, Immunoglobulin
  • Germinal Center / cytology
  • Germinal Center / immunology
  • Immunity, Mucosal
  • Immunization
  • Immunoglobulin A / blood
  • Immunoglobulin D / metabolism
  • Immunoglobulin E / blood
  • Immunoglobulin G / biosynthesis*
  • Immunoglobulin G / blood
  • Immunoglobulin M / deficiency*
  • Immunoglobulin M / genetics*
  • Immunoglobulin mu-Chains / genetics
  • Lymphoid Tissue / cytology
  • Lymphoid Tissue / immunology
  • Mice
  • Mice, Inbred BALB C
  • Mice, Mutant Strains
  • Mutation
  • Receptors, Antigen, B-Cell / genetics*


  • Antigens
  • Immunoglobulin A
  • Immunoglobulin D
  • Immunoglobulin G
  • Immunoglobulin M
  • Immunoglobulin mu-Chains
  • Receptors, Antigen, B-Cell
  • Immunoglobulin E