We used cryopreserved peripheral blood mononuclear cells collected from 1860 Cardiovascular Health Study participants (average age 80.2 years) and flow cytometry immunophenotyping to evaluate the longitudinal relationships of naive (CD45RA+), memory (CD45RO+), senescent (CD28−), and T effector memory RA+ (TEMRA) (CD28−CD57+CD45RA+) CD4+ and CD8+ T cells, and memory B cells (CD19+CD27+), with the risk of incident DM. Here, CD28 is linked to diabetes mellitus.