CD22/CD3 Antibodies

Target Information

CD22 (BL-CAM) is a type I transmembrane glycoprotein expressed mainly on mature B cells and many B cell lymphomas, including hairy cell leukemia and diffuse large B cell lymphoma, but not classical Hodgkin lymphoma. It exists as two isoforms (CD22α and CD22β, 130 and 140 kDa) generated by alternative splicing. The extracellular region contains seven Ig-like domains that bind α2,6-linked sialic acids on epithelial, endothelial, B, and T cells. These interactions may be masked by binding to sialic acids on the same cell (cis interactions). CD22 expression occurs in later stages of B cell development, making it useful for identifying mature B cell leukemias. Its cytoplasmic tail contains six tyrosine residues within immunotyrosine-based inhibitory motifs (ITIMs) and activation-like motifs. Upon B cell receptor (BCR) engagement, these residues are phosphorylated. CD22 can positively regulate signaling through Src family kinases and negatively regulate it by recruiting phosphatases via SH2 domains, which dampen BCR signaling. Through this dual regulatory role, CD22 helps fine-tune B cell activation and serves as an important diagnostic and research marker.

The CD3 complex, composed of gamma, delta, epsilon, and zeta subunits, is essential for T cell receptor (TCR) assembly and surface expression. These immunoglobulin superfamily proteins are encoded by closely linked genes on chromosome 11. CD3 is expressed on thymocytes and all mature T cells, but not on B or NK cells. CD3 transmits antigen-recognition signals into T cells via tyrosine-based motifs in its cytoplasmic tails. TCR crosslinking activates intracellular pathways that lead to T cell activation, proliferation, survival, or growth arrest. CD3 defects cause immunodeficiency, underscoring its critical role in immune function.