From HON News, signs of further progress in generating new T-cells for people with damaged immune systems: "T-cells are one the of the body's main defenses against disease. In this study, researchers demonstrated that it is possible to convert embryonic stem cells into blood-forming stem cells that, in turn, can turn into the helper T-cells. ... The human embryonic stem cells were incubated on mouse bone marrow support cells, which converted the embryonic stem cells into blood-forming cells. These blood-forming cells were then injected into a human thymus gland that had been implanted in a mouse. The thymus gland converted the blood-forming cells into T-cells." It's unclear as to whether this sort of strategy would help the aging immune system - there may be plenty of T-cells, but their programming has become unhelpful.