B cell linker protein (BLNK), also known as SLP-65 or BASH, is an adaptor molecule that plays key roles in B cell activation and B cell antigen receptor (BCR) engagement. BLNK acts at the interface between BCR-associated Syk and downstream signaling cascades. BLNK has multiple SH2 binding motifs (YXXP) at its amino terminus and an SH2 domain at its carboxy terminus. After BCR ligation, BLNK is phosphorylated by Syk at multiple YXXP motifs including Tyr72, Tyr84, Tyr96, and Tyr178 . These phosphorylated motifs provide docking sites for signaling molecules, such as BTK, PLC?, and Vav. These signaling molecules bind to BLNK through their SH2 domains and together activate downstream signaling pathways. Through its SH2 domain, BLNK can also interact with tyrosine-phosphorylated targets, such as HPK1, thereby recruiting them to the BCR complex for signaling.