Siglec-G is a B1 cell-inhibitory receptor that controls expansion and calcium signaling of the B1 cell population

Nat Immunol. 2007 Jul;8(7):695-704. doi: 10.1038/ni1480. Epub 2007 Jun 17.


B1 cells are an important cell population for the production of natural antibodies and for antibacterial immunoglobulin responses. Here we identified the mouse protein Siglec-G as a B1 cell inhibitory receptor. Siglec-G was expressed in a B cell-restricted way, with large amounts present in B1 cells. When overexpressed, Siglec-G inhibited B cell receptor-mediated calcium signaling. Siglec-G-deficient mice had massive expansion of the B1a cell population, which began early in development and was B cell intrinsic. Siglec-G-deficient mice had higher titers of natural IgM antibodies but not a higher penetrance of IgG autoantibodies. Siglec-G-deficient B1 cells showed a strongly enhanced calcium signaling. Our results demonstrate that Siglec-G-dependent negative regulation exists in B1 cells, which may explain the naturally muted signaling response of B1 cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • B-Lymphocyte Subsets / immunology*
  • B-Lymphocyte Subsets / metabolism*
  • Calcium Signaling / genetics
  • Calcium Signaling / immunology*
  • Cell Line
  • Cell Proliferation*
  • Chickens
  • Cloning, Molecular
  • Down-Regulation / genetics
  • Down-Regulation / immunology
  • Lectins / deficiency
  • Lectins / genetics
  • Lectins / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Molecular Sequence Data
  • N-Acetylneuraminic Acid / metabolism*
  • Receptors, Antigen, B-Cell / deficiency
  • Receptors, Antigen, B-Cell / genetics
  • Receptors, Antigen, B-Cell / physiology*
  • Sialic Acid Binding Immunoglobulin-like Lectins


  • Lectins
  • Receptors, Antigen, B-Cell
  • Sialic Acid Binding Immunoglobulin-like Lectins
  • Siglecg protein, mouse
  • N-Acetylneuraminic Acid

Associated data

  • GENBANK/EF419770