A wide array of published studies suggest the positive association between exercise and cancer—notably, that exercise may reduce the risk of getting initial incidences of several different types of cancers, may often improve prognosis in cancer patients, and may reduce the risk of recurrence and secondary cancers survivors of some types of cancers. However, the mechanism behind these phenomena has been unknown. Laura Bilek, from University of Nebraska Medical Center (Nebraska, USA), and colleagues studied a group of 16 cancer survivors, all but one of who recently finished chemotherapy cancer treatment, the researchers focused on T cells, a type of immune cell that attacks a variety of infectious agents as well as cancer cells.  They took blood samples before and after a 12-week exercise program in which the subjects participated.  Analyzing the T cells, the team found that a significant portion of these immune cells converted from a senescent form, which isn't as effective at combating disease, to a naïve form, ready to fight cancer and infections.   Commenting that: "What we're suggesting is that with exercise, you might be getting rid of T cells that aren't helpful and making room for T cells that might be helpful," the lead investigator submits that this finding highlights the importance of exercise for all, including those with cancer and cancer survivors.