Relation of IRF4 expression to disease progression and the immune phenotype in human CLL patients. (A) Primary CLL cells derived from the blood of 98 chemonaive CLL patients and B cells derived from the blood of 9 healthy donors were purified and mRNA measured by real-time PCR. The mRNA expression ratio normalized to 18S and the mean expression in healthy donors is shown. (B) Kaplan-Maier analysis showing TTFT intervals for the IRF4^low and IRF4^high CLL patient group. The cutoff to discriminate between IRF4 groups was calculated by ROC analysis and Youden index calculation. (C) GSE39671 data⁴⁶  were used for Kaplan-Maier analysis showing TTFT intervals in the IRF4^low and IRF4^high group. Group cutoffs were calculated using ROC analysis and Youden index calculation. (D) GSE39671 gene expression data⁴⁶  were analyzed for differentially expressed genes (P < .05) in IRF4^low and IRF4^high CLL patients. Differentially expressed genes were filtered using the murine gene list GO: 0042210 and are depicted as heatmap using unsupervised clustering. (E) The percentage of CD4⁺ and (F) CD8⁺ naïve T cells and (G) CD86⁺ CLL cells was analyzed by flow cytometry and correlated to IRF4 expression measured by real-time PCR. (H) CIITA was measured by real-time PCR in IRF4^low and IRF4^high CLL patients. CIITA expression ratios are depicted as delta CT ratio, normalized to 18S. (I) Heatmaps of HLA genes extracted from Affymetrix Gene chip data derived from the public dataset GSE21029⁴⁷  are shown for BM samples of CLL patients. IRF4 expression is shown on the x-axis using a declining expression gradient.