The overexpression of the HLA-DQA1 and HLA-DQB1 genes encoding subunits of MHC class II molecules, which are responsible for antigen presentation by immune cells, was demonstrated in T2D individuals, proving the commonality of immune response activation in T1D, T2D, and latent autoimmune diabetes in adults. This evidence concerns the gene HLA-DQA1 and type 2 diabetes mellitus.