Type 1 diabetes impairs the mobilisation of highly-differentiated CD8+T cells during a single bout of acute exercise.

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease that targets and destroys insulin-secreting pancreatic beta cells. Beta cell specific T cells are highly differentiated and show evidence of previous antigen exposure. Exerciseinduced mobilisation of highly-differentiated CD8+ T cells facilitates immune surveillance and regulation. We aimed to explore exercise-induced T cell mobilisation in T1D. In this study, we compared the effects of a single bout of vigorous intensity exercise on T cell mobilisation in T1D and control participants. N=12 T1D (mean age 33.2yrs, predicted VO2 max 32.2 mL/(kg·min), BMI 25.3Kg/m2) and N=12 control (mean age 29.4yrs, predicted VO2 max 38.5mL(kg.min), BMI 23.7Kg/m2) male participants completed a 30-minute bout of cycling at 80% predicted VO2 max in a fasted state. Peripheral blood was collected at baseline, immediately post-exercise, and 1 hour post-exercise. Exercise-induced mobilisation was observed for T cells in both T1D and control groups. Total CD8+ T cells mobilised to a similar extent in T1D (42.7%; p=0.016) and controls (39.7%; p=0.001). CD8 effector memory CD45RA+ (EMRA) subset were the only T cell lineage subset to be significantly mobilised in both groups though the percentage increase of CD8+ EMRA was blunted in T1D (T1D (26.5%) p=0.004, control (66.1%) p=0.010). Further phenotyping of these subsets revealed that the blunting was most evident in CD8+ EMRA that expressed adhesion (CD11b: T1D 37.70%, Control 91.48%) and activation markers (CD69: T1D 29.87%, Control 161.43%), and appeared to be the most differentiated (CD27-CD28-: T1D 7.12%, Control 113.76%). CD4+ T cells mobilised during vigorous intensity exercise in controls (p=0.001), but not in T1D. The blunted mobilisation response of particular T cell subsets was not due to CMV serostatus or apparent differences in exertion during the exercise bout as defined by heart rate and RPE. Predicted VO2 max showed a trend to be lower in the T1D group than the control group but is unlikely to contribute to this blunted response. We postulate the reasons for a blunted mobilisation of differentiated CD8+ EMRA cells includes differences in blood glucose, adrenaline receptor density, and sequestration of T cells in the pancreas of T1D participants. In conclusion, mobilisation of CD8+ EMRA and CD4+ subsets T cells is decreased in people with T1D during acute exercise.