The ligand-binding domain of siglec-G is crucial for its selective inhibitory function on B1 cells

Stefan Hutzler, Lamia Özgör, Yuko Naito-Matsui, Kathrin Kläsener, Thomas H. Winkler, Michael Reth, Lars Nitschke

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

Siglec-G is an inhibitory receptor on B1 cells. Siglec-G-deficient mice show a large B1 cell expansion, owing to higher BCR-induced Ca2+ signaling and enhanced cellular survival. It was unknown why Siglec-G shows a B1 cell-restricted inhibitory function. With a new mAb we could show a comparable Siglec-G expression on B1 cells and conventional B2 cells. However, Siglec-G has a different ligand sialic acid-binding pattern on peritoneal B1 cells than on splenic B cells, and its sialic acid ligands are expressed differentially on these two B cell populations, suggesting that cis-ligand binding plays a crucial role on B1 cells. This observation was further studied by generation of Siglec-G knockin mice with a mutated ligand-binding domain. These mice show increased B1 cell numbers, increased B1 cell Ca2+ signaling, better B1 cell survival, and changes in the B1 cell Ig repertoire. These phenotypes are very similar to Siglec-G-deficient mice. The mutation of the ligand-binding domain of Siglec-G strongly reduces the Siglec-G-IgMassociation on the B cell surface. Thus, Siglec-G sialic acid-dependent binding to the BCR is crucial for the B1 cell-restricted inhibitory function of Siglec-G and is regulated in an opposite way to that of the related protein CD22 (Siglec-2) on B cells.

Original languageEnglish
Pages (from-to)5406-5414
Number of pages9
JournalJournal of Immunology
Volume192
Issue number11
DOIs
Publication statusPublished - 01-06-2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology

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