Ig-β/CD79b

Ig-beta (CD79b, B29) is the partner chain of Ig-alpha in the B-cell receptor, anchoring membrane immunoglobulin molecules that cannot reach the surface on their own. Its single extracellular Ig-like domain and cytoplasmic ITAM complement those of CD79a, and phosphorylated CD79b helps recruit Syk and BTK after antigen engagement. Beyond signaling, CD79b controls the intracellular transport and degradation routing of the BCR. Biallelic CD79B loss produces a phenotype resembling severe B-cell deficiency, whereas in diffuse large B-cell lymphoma the chain is a validated drug target: polatuzumab vedotin delivers cytotoxins to CD79b-positive malignant cells.