We found that killer immunoglobulin-like receptor (KIR) genes, enterovirus infection in gut cells, and gut microbiota dysbiosis with the predominance of Bacteroides spp. also play a role in the pathogenesis and development of symptoms of CD in patients with the previous diagnosis of T1DM. CD4+ and CD8+ cell levels vary among patients and studies, consequently, more study on this topic is needed. The gene discussed is CD8A; the disease is type 1 diabetes mellitus.