Western blot was performed using Rabbit anti-Human IgM Secondary Antibody (Product # SA1-400) and an ~80 kDa band corresponding to Human IgM Heavy Chain was observed in Raji, Ramos and Daudi but not in IM-9, ARH-77, MOLT-4 and Jurkat8203. Whole cell extracts (30 µg) of IM-9 (Lane 1), ARH-77 (Lane 2), Raji (Lane 3), Ramos (Lane 4), Daudi (Lane 5), MOLT-4 (Lane 6) and Jurkat (Lane 7) were electrophoresed using NuPAGE™ 4-12% Bis-Tris Protein Gel (Product # NP0322BOX). Resolved proteins were then transferred onto a nitrocellulose membrane (Product # IB23001) by iBlot® 2 Dry Blotting System (Product # IB21001). The blot was probed with Product # SA1-400 (1:2000 dilution) and detected by chemiluminescence with Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Recombinant Secondary Antibody, HRP Conjugate (Product # A27036, 1:20,000 dilution) using the iBright FL1500 (Product # A44115). Chemiluminescentdetection was performed using Novex® ECL Chemiluminescent Substrate Reagent Kit (Product # WP20005). Raji, Ramos and Daudi are known to express IgM whereas IM-9 and ARH-77 express IgG and are negative for IgM. MOLT-4 and Jurkat, being T-cell lines, do not express immunoglobulins (DOI:10.1002/eji.1830100305; 10.3791/3573; 10.1016/0022-1759(94)00286-6; PMID: 566614).