The CD79a antigen (Immunoglobulin binding protein-1, IGBP-1) is an alpha/beta heterodimer cell membrane protein required in cooperation with CD79b for the initiation of the signal transduction cascade activated by binding of antigen to the B-cell antigen receptor comple, Xenopus/Amphibian, (BCR). This cascade leads to BCR comple, Xenopus/Amphibian, internalization, trafficking to late endosomes and antigen presentation. CD79a is also required for BCR surface e, Xenopus/Amphibian,pression and efficient differentiation of pro- and pre-B-cells. CD79a interacts with numerous kinases such as SYK, BLNK, Src-family tyrosine kinases. Defects in CD79a are a cause of non-Bruton type agammaglobulinemia, an immunodeficiency disease of the B-cell maturation pathway.