Differential expression of IL-4-inducible genes and IL-4 in GCB-like and ABC-like DLBCL. (A) DNA microarray analysis of IL-4-inducible genes whose expression is significantly higher in GCB-like than in ABC-like DLBCL tumors. DLBCL cases are ordered and subdivided into GCB and ABC subtypes as defined in Figure 1 of Alizadeh et al.¹  Relative expression is displayed according to the color scale shown. (B) Expression of IL-4 mRNA in GCB-like (▪) and ABC-like DLBCL tumors (▴). IL-4 mRNA expression was measured using real-time RT-PCR as described in “RNA isolation, RT reaction, and real-time PCR.” (C) IL-4-induced gene expression in GCB-like and ABC-like DLBCL cell lines. Expression of IL-4-inducible HGAL, IL-4Rα, and CD23 mRNA was measured in triplicates by quantitative RT-PCR in unstimulated (▦) and IL-4-stimulated (100 U/mL, □) DLBCL cell lines, as described in “RNA isolation, RT reaction, and real-time PCR.” (D) Mean fluorescence intensity of surface IL-4Rα as examined by flow cytometry (▦) in comparison to isotype control (□) in GCB-like and ABC-like DLBCL cell lines. Error bars depict standard deviation (SD).