University of California - San Diego Apr 17 2025 Our immune systems weaken as we get older, making fewer cells that fight infection and help us recover from illness and injury. Scientists aren't completely sure why. They may have a better idea now, however, thanks to a new study in GeroScience . "Immune cell changes occur during aging for a number of reasons, but we still don't completely understand why we have fewer antibody-producing cells with age," said Leslie Crews, Ph.D., assistant