B-cell differentiation antigen CD22 (CD22)

B-cell differentiation antigen CD22 is a 140 kDa type I transmembrane glycoprotein specifically expressed on the surface of mature B lymphocytes and serves as an inhibitory receptor for B-cell receptor (BCR) signaling. Structurally, CD22 is composed of an extracellular region with seven immunoglobulin domains and a cytoplasmic tail containing immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Functionally, it inhibits excessive BCR signaling to maintain immune tolerance and prevent autoimmunity. CD22 recognizes alpha2-6-linked sialic acid-containing glycans on glycoproteins of various immune and non-immune cells, mediating both cell adhesion and B cell homing. Due to its restricted expression on B cells and role as an immune checkpoint, it is an established therapeutic target in B cell malignancies and autoimmune diseases, targeted by monoclonal antibodies and chimeric antigen receptor T-cell therapies.

Other names

Cluster of differentiation 22SIGLEC-2Sialic acid-binding Ig-like lectin 2BL-CAMLyb-8

Monoclonal antibodies (e.g., epratuzumab) bind CD22, inducing B cell depletion through antibody-dependent cellular cytotoxicity (ADCC) or other immune mechanisms. CAR-T cells engineered against CD22 recognize and destroy CD22-positive B cells.