Our efforts to identify a signature of immune system age, as well as cellular phenotypes associated with T1D, provide a number of additional targets for consideration in precision medicine–based therapies (e.g., CXCR3+ T cells, the PD-1 costimulatory axis, antigen presentation on monocytes, specifically in individuals with HLA-DR4). This evidence concerns the gene CXCR3 and type 1 diabetes mellitus.