Western blot was performed using Btk Recombinant Rabbit Monoclonal Antibody (SN69-07) (Product # MA5-32291) and a 75 kDa band corresponding to BTK was observed across tested panel. Whole cell extracts (40 µg lysate) of Daudi (Lane 1), Raji (Lane 2), Ramos (Lane 3), Jurkat (Lane 4) were electrophoresed using NuPAGE™ 4-12% Bis-Tris Protein Gel (Product # NP0321BOX), 10 well. Resolved proteins were then transferred onto a nitrocellulose membrane (Product # IB23001) by iBlot® 2 Dry Blotting System (Product # IB21001). The blot was probed with the primary antibody (1:1000 dilution) and detected by chemiluminescence with Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Recombinant Secondary Antibody, HRP (Product # A27036, 1:20,000 dilution) using the iBright™ FL1500 Imaging System (Product # A44115). Chemiluminescent detection was performed using SuperSignal™ West Dura Extended Duration Substrate (Product # 34076). Lack of signal in low expressing Jurkat cells confirm specificity.