There are several aberrant signaling pathways involving various cytokines, including interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 9 (IL-9), and interleukin 10 (IL-10), in CLL. Here, IL4 is linked to B-cell chronic lymphocytic leukemia.