C/G predominance of BCL2 mutations and AID expression in FL. (A) Depiction of bp preference of mutations in the FL discovery (left), FL validation (middle), and DLBCL (right) cohorts. The size of letters corresponds to the frequency with which that nucleotide is mutated in the BCL2 coding strand. (B) Transition and transversion load in FL discovery, FL validation, and DLBCL cohorts. Within each group, transitions are depicted in orange, transversions in red, and other changes in gray. (C) Images of FL validation cohort lymph node biopsies from diagnosis showing low (left) and high (right) staining after reaction with anti-AID primary antibody and peroxidase-labeled secondary antibodies. (D) RT-PCR was performed in 21 FL patient samples to detect AID expression differences at the mRNA level. Actin was used as an RNA loading control. (E) AID score (calculated as described in “Methods”) from 128 pretreatment FL validation cohort diagnostic samples depicted as a function of BCL2 mutation status (P < .0001).