(From News-Medical.net). Scientists at the Oregon Health and Science University have proposed an explanation for the deterioration of the immune system with age. "Throughout our lives, we have a very diverse population of T cells in our bodies. However, late in life this T cell population becomes less diverse ... [one type of cell] can grow to become more than 80 percent of the total [T-cell] population. The accumulation of this one type of cell takes away valuable space from other cells, resulting in an immune system that is less diverse and thus less capable in effectively locating and eliminating pathogens." Assuming this research is validated, work can now start on methods of balancing the cell population to prevent age-related immune system decline.