The proportion of CD4+ T-cells remained similar in hosts injected with IL-15Rc-secreting leukemia cells, naïve mice and mice injected with the parent line (under 2.5%), but was significantly increased to 9.72 ± 0.51% in the IL-15sol model, maybe suggesting the need for IL-15sol in the expansion of CD4+ helper T-cells, known to be vital for adaptive immune responses. This evidence concerns the gene CD4 and leukemia.