B-cell antigen receptor complex-associated protein beta chain (CD79b) is also known as B-cell-specific glycoprotein B29, Ig-beta,Immunoglobulin-associated B29 protein, B29 and IGB, which is a single-pass type I membrane protein containing one Ig-like V-type ( immunoglobulin-like ) domain and one ITAM domain.CD79b is required in cooperation with CD79A for initiation of the signal transduction cascade activated by the B-cell antigen receptor complex (BCR).CD79b can enhance phosphorylation of CD79A, possibly by recruiting kinases which phosphorylate CD79A or by recruiting proteins which bind to CD79A and protect it from dephosphorylation. Defects in CD79b are the cause of agammaglobulinemia type 6 (AGM6) that is a primary immunodeficiency characterized by profoundly low or absent serum antibodies and low or absent circulating B cells due to an early block of B-cell development.