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CD22

CD22 (cluster of differentiation-22) is a cell surface sialic acid binding Ig-like lectin (SIGLEC2 or SIGLEC-2) that is involved in B-cell and B-cell interactions. It is mainly expressed on mature B cells and it is an immunoglobulin protein that contains six Ig-like C2-type domains and one Ig-like V-type domain in the extracellular portion for ligand binding and four cytoplasmic immunoreceptor tyrosine-based inhibitor motifs (ITIM) for downstream cellular signaling modulations.

CD22 interacts with ligands including Grb2, PTPN6, LYN, SHC1, and INPP5D with a high preference towards alpha-2,6-linked sialic acid. The ligand binding leads to the phosphorylation of CD22 cytoplasmic portion and mediates B cell receptor (BCR) signaling. Overall, CD22 is regarded as a regulatory molecule that tunes-down immune system activity and prevents the development of autoimmune diseases. Mutations and abnormal expressions of CD22 is often associated with refractory hematologic cancer and it is being exploited as a target for ADC-based immunotherapies using certain immunotoxins.

Entrez Gene ID: 933
UniProt ID: P20273