CD22 & saporin

CD22 is a B-cell-specific transmembrane glycoprotein belonging to the SIGLEC (sialic acid-binding immunoglobulin-like lectin) family. It is encoded by the CD22 gene located on chromosome 19q13.1. CD22 plays a crucial role in B-cell signaling and immune response modulation. It acts primarily as an inhibitory co-receptor that regulates B-cell receptor (BCR) signaling, thereby preventing overactivation of B cells and reducing the risk of autoimmunity. CD22 binds to sialylated glycans and recruits SHP-1 (Src homology region 2 domain-containing phosphatase-1), a phosphatase that dampens signaling cascades.

Saporin is a so-called ribosome inactivating protein (RIP), due to its N-glycosidase activity, from the seeds of Saponaria officinalis (common name: soapwort).Saporin depurinate the ribosomal RNA in a specific position; rendering the large subunit of ribosomes unable to bind the elongation factors. The consequent arrest of protein synthesis is responsible for the cytotoxicity.