IL-21 gene expression signature is increased in CLL cells cultured with autologous activated T cells and in lymph nodes from CLL patients. An IL-21 score was computed as the average of the fold change in messenger RNA expression of the 51 genes shown in Figure 3A and in supplemental Table 3. (A) IL-21 score for CD40 versus CD40 + IL-21 for samples 2, 5B, 11, and 30. (B) IL-21 score for CD40 versus Tact, for samples 2, 5B, 19, 24, and 27. (C) IL-21 score calculated from published data of Herishanu et al³⁶  from BM and PB, in relation to the corresponding level in PB.