CD4 and B-cell chronic lymphocytic leukemia: Helper T cells play both pro- and antitumor roles in CLL, and expansion of various CD4+ T cell subsets (e.g., Th1, Th2, Th17, Tregs, follicular Th cells) have been observed in patients with CLL, supporting the intricate involvement of CD4+ T cells in CLL pathogenesis (68).