Salmonella infection leads to severe intestinal inflammation and increased CD4+FoxP3+ Treg cells in streptozotocin-induced hyperglycemic mice

Hyperglycemia promotes the growth and reproduction of bacteria, thereby increasing the probability of infection, which also causes rebound hyperglycemia. Therefore, the interactions of infection and hyperglycemia lead to the progression and deterioration of these diseases. Type 1 diabetes mellitus (T1DM) is an autoimmune disease. Studies have shown that regulatory T cells (Tregs) play a key role in maintaining islet-specific tolerance. Treg deficiency may lead to the development of early pancreatitis and T1DM, and sufficient amounts of Tregs can restore this tolerance, thereby inhibiting the occurrence of T1DM. Moreover, different subpopulations of dendritic cells (DCs) play an important role in activating autoreactive T cells and inducing autoimmune tolerance to autoantigens, which are closely related to the functional diversity caused by different phenotypes, maturation status, and the immune microenvironment of DC subpopulations. In the present study, we used streptozotocin-induced hyperglycemic mice to model T1DM and induced a Salmonella infection in the mouse model, leading to aggravated inflammation, which resulted in an elevated proportion of CD103(+)CD11b(+) DCs and a significantly elevated proportion of CD4(+)FoxP3(+) Tregs in the intestinal lamina propria. After co-culturing CD4(+) T cells and DCs, we found that CD103(+)CD11b(+) DCs could significantly promote the proliferation of CD4(+) T cells. The elevated proportions of CD4(+)FoxP3(+) Tregs were considered to be correlated with the increased number of CD103(+)CD11b(+) DCs.