Villaudy et al. (2011) reported that HTLV-1 induces alterations of the thymus of Rag2-/IL-2R γc- mice leading to expanded populations of mature CD4+/CD25+ T cells and other pathological features such as splenomegaly and lymphomas as compared to mock-infected mice. This unique model system was then used to test anti-cancer drugs, further illustrating the usefulness of the model (Martin et al., 2011; Villaudy et al., 2011). The gene discussed is IL2RA; the disease is Splenomegaly.