CD4 and B-cell chronic lymphocytic leukemia: Herein, we illustrate the feasibility of polarizing CD4<sup>+</sup> T cells from the Eμ-TCL1 murine model, the most representative model for human CLL, into Th17 phenotype, employing a protocol of T-cell activation through the inducible co-stimulator (ICOS) alongside a polarizing cytokine mixture.