As we overlay genetics in T1D, the microbiome in diabetes with anti–PD-1 treatment and age-dependent effects on the microbiome, the first strong observation was the confirmation of common outcomes in T1D, such as reduced diversity and an increase of abundance of Bacteroidetes as well as a decrease in Firmicutes and Tenericutes. This evidence concerns the gene PDCD1 and type 1 diabetes mellitus.