CD27 and Sepsis: The proportions of PD-1 and PD-L1 positive T cells were significantly greater in sepsis than in controls (38.90% vs 21.25%, p = 0.0023; 1.9% vs 0.2%, p = 0.0083), as were the corresponding MFI values (780 vs 627, p = 0.0013; 1314 vs 1007, p = 0.0276) (Fig. 2): this was true of CD27+ and CD27- subsets (p < 0.05 for all comparisons) (Additional file 5: Table S4; Additional file 8: Table S5; Additional file 9: Figure S4; Additional file 10: Figure S5).