One possible form of future immune therapy involves growing vast numbers of tailored immune cells, far more than would ever naturally be present in the body, and then infusing them to sweep away the target problem - cancer being an early target for this sort of approach. Here is some groundwork for these future therapies: "Adult stem cells from mice converted to antigen-specific T cells - the immune cells that fight cancer tumor cells - show promise in cancer immunotherapy and may lead to a simpler, more efficient way to use the body's immune system to fight cancer ... Tumors grow because patients lack the kind of antigen-specific T cells needed to kill the cancer. An approach called adoptive T cell immunotherapy generates the T cells outside the body, which are then used inside the body to target cancer cells. ... It is complex and expensive to expand T cell lines in the lab, so researchers have been searching for ways to simplify the process. [They] found a way to use induced pluripotent stem (iPS) cells, which are adult cells that are genetically changed to be stem cells. ... Any cell can become a stem cell. It's a very good approach to generating the antigen-specific T cells and creates an unlimited source of cells for adoptive immunotherapy. ... By inserting DNA, researchers change the mouse iPS cells into immune cells and inject them into mice with tumors. After 50 days, 100 percent of the mice in the study were still alive, compared to 55 percent of control mice, which received tumor-reactive immune cells isolated from donors."