Abstract: The teachings are directed to an immunocompetent xenograft model. The model comprises an immunodeficient animal modified to have a reconstituted immune system, wherein a xenograft is transplanted in the animal and allowed to establish for an establishment period of at least about 10 days. The xenograft simulates a tissue in a subject in need of a treatment. In these embodiments, the reconstituted immune system is created after the establishment period, and is created by administering a total number of T-cells to the animal. The total number of T-cells consists of a preselected number of responsive T-cells, a preselected number of non-responsive T-cells, and a preselected ratio of responsive T-cells to total T-cells. The preselected number of responsive T-cells simulates a number of responsive T-cells in the subject, and the ratio of the number of responsive T-cells to total T-cells ranges from about 1:100,000 to about 30:100,000.