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 20 h 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.