Recombinant Human CD22 (C177-GRP)

Cluster of differentiation 22 (CD22, Siglec-2) is a B cell–restricted transmembrane glycoprotein of the immunoglobulin superfamily that functions primarily as an inhibitory co-receptor for the B cell receptor (BCR). Through immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its cytoplasmic tail, CD22 recruits phosphatases such as SHP-1 to dampen BCR-mediated signaling, thereby helping to maintain B cell tolerance and prevent excessive activation. Structure and lectin function CD22 contains multiple extracellular Ig-like domains, with the N-terminal V-set domain mediating binding to sialic acid–containing ligands, giving CD22 lectin-like adhesive properties that influence cell–cell interactions and B cell trafficking. The preferential recognition of α2,6-linked sialic acids on glycoproteins places CD22 within the sialic acid–binding Ig-like lectin (Siglec) family and allows it to engage both cis-ligands on the same B cell and trans-ligands on neighboring cells. Role in B cell signaling As an inhibitory co-receptor, CD22 modulates BCR signaling thresholds by limiting calcium flux and downstream activation pathways after antigen engagement. This negative regulatory role is critical for tuning responses to self versus foreign antigens, shaping B cell selection, and constraining autoreactive clones. Relevance as a therapeutic target Because CD22 is selectively expressed on most mature B cells and contributes to controlling activation, it has emerged as an attractive target for antibody- and ligand-directed therapies in B cell malignancies and autoimmune diseases. In addition, targeting CD22 has been explored as a strategy to transiently manipulate B cell responses, including approaches described as “universal vaccination” concepts aimed at accelerating antibody production and enhancing host defense against acute infections.