BLNK is a cytoplasmic linker or adaptor protein which has a significant role in B cell development. B-cell linker （BLNK） is essential for normal B-cell development. BLNK bridges B cell receptor-associated kinase activation with downstream signaling pathways， thus affecting different biological functions. BLNK associates with the effector proteins GRB2， Vav， NCK and PLC-g following activation of the B cell receptor. BLNK is phosphorylated by the Syk tyrosine kinase， which in turn permits activation of downstream effector proteins including GRB2 and PLC-g. Mutations in the BLNK gene cause hypoglobulinemia and absent B cells， a disease in which the pro- to pre-B-cell transition is developmentally blocked. Deficiency in the BLNK protein is seen in some cases of pre-B acute lymphoblastic leukemia.
