Type 1A diabetes (T1D) is believed to be caused by immune-mediated destruction of β-cells, but the immunological basis for T1D remains controversial. Microbial diversity promotes the maturation and activation of certain immune subsets, including CD161bright CD8+ mucosal associated invariant T (MAIT) cells, and alterations in gut mucosal responses have been reported in type 1 diabetics (T1Ds). We analyzed T cell populations in peripheral blood leukocytes from juvenile T1Ds and healthy controls. We found that proportion and absolute number of MAIT cells were similar between T1Ds and controls. Furthermore, while MAIT cell proportions increased with age among healthy controls, this trend was not observed among long-standing T1Ds. Additionally, the CD27- MAIT cell subset is significantly increased in T1Ds and positively correlated with HbA1c levels. However, after T1Ds are stratified by age, the younger group has significantly increased proportions of CD27- MAIT cells compared to age-matched controls, and this proportional increase appears to be independent of HbA1c levels. Finally, we analyzed function of the CD27- MAIT cells and observed that IL-17A production is increased in CD27- compared to CD27+ MAIT cells. Overall, our data reveal disparate MAIT cell dynamics between T1Ds and controls, as well as signs of increased MAIT cell activation in T1Ds. These changes may be linked to hyperglycemia and increased mucosal challenge among T1Ds.

Type II diabetes is an inflammatory disease marked by chronic immune activation. Our goal is to describe the fundamental distinctions in the immune system of the db/db mouse. Serum was collected for a 58-factor immunoassay. Splenic leukocytes were isolated for six panels of flow cytometry to examine immune subsets and activation states. Db/db mice exhibit higher levels of proinflammatory factors such as C-reactive protein, granulocyte chemotactic protein-2, monocyte chemotactic protein-1, macrophage inflammatory protein-2, IL1α, and T-RANTES and lower levels in regulatory IL10. Flow cytometry data revealed upregulation of the adhesion molecule CD11b on neutrophils, monocytes and macrophages. Macrophages also expressed increased levels of costimulatory molecule CD80. Inflammatory DC were increased while regulatory DC were decreased. Pre-germinal center B cells were decreased. Plasma and memory B cells were increased with an increase in CD22 maturity marker. FoxP3+ T regs were decreased with a reciprocal increase in CD127. Total CD8 T cells were increased with greater naive populations. Unactivated NK cells were increased, and all NK populations had decreased Ly49H and KLRG1. Above results were significant with p<0.05. Baseline immune activation in db/db mice is marked by increased circulating proinflammatory factors, decreased circulating regulatory factors, increased activation of innate and humoral immunity, and suppressed regulatory and cellular immunity.