CD4 and B-cell chronic lymphocytic leukemia: Our finding that the coculture of CLL B cells with autologous CD4+ T cells leads to higher percentages of IL-17F-expressing Th17 cells (Fig. 4) suggests that the CLL B cell itself, in certain contexts, has the capacity to trigger a signaling pathway(s) in the T cell that drives Th17 differentiation or expansion.