The AID protein is expressed in both GCB- and ABC-like DLBCLs. (Top) AID protein levels, measured by Western blotting and normalized for β-actin as described in “Materials and methods,” are shown in individual DLBCL samples classified by gene expression profiling as GCB-like (○), ABC-like (•), and type 3 (). Two different scales are used for the primary biopsies (left) and the cell lines (right), because lower AID levels were consistently observed in the former ones, likely due to the presence of contaminating nontumor cells. (Bottom) Histograms show the average AID protein expression levels in the 3 groups. Error bars indicate standard deviations.