Consistently, transgenic experiments over-expressing so-called T-cell growth cytokines such as IL-15 and IL-7 results in the development of T-cell leukemia in these mice but that is only limited to CD8 (and NK) lineages (Rich et al., 1993; Fehniger et al., 2001; Sato et al., 2011). This evidence concerns the gene CD8A and T-cell leukemia.