Differential alterations of tissue T-cell subsets after sepsis

Among immune cells in responding to sepsis, macrophages and neutrophils have been extensively studied, while the contribution of T lymphocytes and natural killer T (NKT) cells is less well characterized. Here we monitored tissue specific changes of T cell subsets in male C57BL/6 mice subjected to sham operation or cecal ligation and puncture (CLP) to induce polymicrobial sepsis. Thymus, spleen, liver, lungs and blood were processed and analyzed 20h later. Total lymphocyte count showed a significant reduction in septic thymus, spleen and blood but not in lungs and liver. The septic thymi were hypocellular with severe reduction in cell numbers of immature CD4⁺CD8⁺ subset. CD4⁺ T and CD8⁺ T lymphocyte numbers in septic spleens were also significantly reduced, but the frequency of CD4⁺CD25⁺ Tregs was significantly increased. In addition, naïve and Tcm CD4⁺ T cell numbers were significantly reduced in the septic spleens. By contrast, in septic liver the CD8⁺ T cell numbers were significantly increased, whereas NKT cell numbers were reduced, but more activated with increased CD69 and CD25 expression. In the septic lungs, the CD4⁺ T and CD8⁺ T cell numbers showed no significant change, whereas they were severely reduced in the septic blood. Overall, this study provides important information on the alterations of different T-cell subsets in various tissues after sepsis.