AID is inducible in both WM and IgM MGUS. (A) AID expression is compared before and after CD40L/IL-4 stimulation by bulk RT-PCR. (B) Aliquots of 1000 cells/tube from unstimulated CD20⁺ B cells were analyzed for AID transcripts (left side of each row) or single CD20⁺ cells from poststimulated samples were sorted and analyzed for clonotypic and AID transcripts (right side of each row).