Effect of signaling inhibitors on anti-IgM–induced UPR activation. Cells were pretreated with dimethylsulfoxide, ibrutinib, or tamatinib for 30 minutes before being stimulated with bead-bound anti-IgM or control antibodies. Expression of PERK, BIP, phosphorylated ERK1/2, and phosphorylated AKT was analyzed at 24 hours. (A) Representative immunoblots. (B) Quantitation of results for all samples (n = 6 for ibrutinib and tamatinib). Graphs show inhibition of PERK/BIP expression with anti-IgM/dimethylsulfoxide–treated cells set to 100%. The statistical significance of differences between control and compound-treated control cells is shown (Student t test).