Abstract: A major type of unwanted cells that accumulate in aging are anergic cytotoxic T-cells. These cells often have virus-specific T-cell receptors, as well as other surface markers that distinguish them from their youthful counterparts, and are thought to play a major role in the decline of the immune system with age. Here we disclose the use of magnetic cell separation methods and apparatuses to remove senescent T-cells defined by the surface markers CD8+, KLRG1+ and CD8+, CD28?. We disclose how these markers are used to remove anergic T-cells from the blood of aged C57BL/6 mice, resulting in lasting rejuvenation of their immunological marker profile. Using antibodies with magnetic microparticles linked to their Fc domains, we first developed a method to use magnets to filter out the unwanted cells from the blood, and later constructed a device that does this automatically.