The diversity of the T cell repertoire in T1D patients was significantly decreased in comparison with T2D patients (P = 7.0E−08 for CD4+ T cells, P = 1.4E−04 for CD8+ T cells) and nondiabetic controls (P = 2.7E−09 for CD4+ T cells, P = 7.6E−06 for CD8+ T cells). This evidence concerns the gene CD8A and type 2 diabetes mellitus.