KIR2DL5⁺CD8⁺ T cells associate with dietary lipid intake and are active in type 1 diabetes

Recent studies have shown that KIR⁺CD8⁺ T cells play a role in suppressing autoimmunity by eliminating pathogenic CD4⁺ T cells. However, their specific role in type 1 diabetes (T1D) remains unclear.

In this study, we enrolled 108 patients diagnosed with T1D and 86 healthy individuals. We conducted flow cytometric analysis to examine the various subtypes of KIR⁺CD8⁺ T cells derived from peripheral blood mononuclear cells. Additionally, CD8⁺ T cells were isolated from the peripheral blood of T1D patients to assess the functions of different KIR⁺CD8⁺ T cell subtypes. To investigate the influence of lipids on the characteristics and activities of these T cell subtypes, the isolated CD8⁺ T cells were cultured with varying concentrations of palmitic acid (PA). Furthermore, we utilized an NSG (NOD scid gamma) mouse adoptive transfer model to assess the impact of dietary lipid intake on the functionality of KIR2DL5⁺CD8⁺ T cells in vivo.

We observed variations in circulating KIR⁺CD8⁺ T cell subtypes between patients with T1D and healthy controls. Notably, we observed a significant negative correlation between the frequencies of circulating KIR⁺CD8⁺ T cells and the titers of ZnT8 autoantibodies in individuals with T1D. Among these subtypes, KIR2DL5⁺CD8⁺ T cells demonstrated a positive association with dietary fat intake, characterized by increased perforin expression and reduced PD-1 expression. Importantly, KIR2DL5⁺CD8⁺ T cells exhibited enhanced proliferative capacity compared to other KIR⁺CD8⁺ T cell subsets. Palmitic acid (PA) was found to enhance the activation of KIR2DL5⁺CD8⁺ T cells and strengthened their ability to suppress CD4⁺ T cell proliferation in T1D patients. Moreover, dietary lipid intake significantly enhanced the functionality of KIR2DL5⁺CD8⁺ T cells in an NSG mouse adoptive transfer model.

Our findings suggest that lipid intake enhances the functionality of human KIR2DL5⁺CD8⁺ T cells and may offer implications for immunotherapy in T1D.