There are approximately 30 trillion cells in a human body and our health is predicated on them properly interacting with and supporting each other, with the immune system playing a particularly pivotal role. One of the defining characteristics of aging is a decline in the proper functioning of our immune system. Centenarians, a rare population of individuals who reach 100 years or more, experience delays in aging-related diseases and mortality which suggests their immune systems remain functional into extreme old age. Led by researchers from Boston University Chobanian & Avedisian School of Medicine and Tufts Medical Center, a new study finds centenarians harbor distinct immune cell type composition and activity and possess highly functional immune systems that have successfully adapted to a history of sickness allowing for exceptional longevity. These immune cells may help identify important mechanisms to recover from disease and promote longevity.