B-cell antigen CD22 (CD22)

B-cell antigen CD22 is a transmembrane glycoprotein expressed predominantly on the surface of mature B lymphocytes. It plays a key role as an inhibitory coreceptor of the B-cell receptor (BCR), setting signalling thresholds for B-cell activation and maintaining immune tolerance by dampening BCR-mediated signaling. Structurally, CD22 belongs to the Siglec family (Siglec-2) and the immunoglobulin superfamily, featuring seven extracellular Ig-like domains that bind specifically to α2,6-linked sialic acid-containing glycans. Upon antigen engagement, its cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMs) are phosphorylated and recruit phosphatases (e.g., SHP-1) that downregulate BCR signaling. CD22 is also involved in B-cell trafficking and adhesion, and its dysfunction or altered expression is implicated in autoimmune diseases and B-cell malignancies. CD22’s restricted expression and endocytic capability have made it an important therapeutic target for monoclonal antibody and antibody-drug conjugate therapies in various hematologic cancers and immune disorders[1][2][3][4][5].

Other names

Siglec-2SIGLEC2Sialic acid-binding Ig-like lectin 2Cluster of differentiation 22

Monoclonal antibodies: target CD22 to induce B-cell depletion via antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), or by delivering conjugated toxins directly to malignant B cells[3]. Antibody-drug/toxin conjugates: binding to CD22 and subsequent internalization allows selective delivery of cytotoxic payloads to B-lineage cells, inducing apoptosis or cell death[3]. Inhibition of BCR signaling: therapeutic agents may modulate CD22 to restore or dampen B-cell activation[1][3][5].