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. Author manuscript; available in PMC: 2009 Oct 28.
Published in final edited form as: Nat Rev Immunol. 2008 Nov;8(11):874–887. doi: 10.1038/nri2417

Figure 4. Glycans in B-cell-receptor activation.

Figure 4

The threshold of B-cell receptor (BCR) activation is modulated by ST6Gal1 and CD22, a member of the Siglec (sialic-acid-binding immunoglobulin-like lectin) family that has a negative role in BCR signalling. CD22 Siglec binding to its glycan ligand promotes homotypic CD22–CD22 interactions, thereby decreasing the frequency of interaction of CD22 with the IgM BCR on mature naive B cells. Loss of CD22 Siglec ligands owing to ST6Gal1 sialyltransferase deficiency markedly increases the co-localization of CD22 with the BCR, thereby increasing the threshold of immune signalling and promoting endocytosis of the BCR in a CD22-dependent manner.