Background  Sepsis is the major cause of death in critically ill patients, but effective treatment strategies for sepsis are still lacking. Fecal microbiota transplantation (FMT) has recently gained concern as a potential treatment for sepsis.

  Objective  To investigate the effects of FMT on the immune status of intestinal T cells and intestinal inflammation in septic mice.

  Methods  C57BL/6 mice aged 8 - 10 weeks were randomly divided into control group, sepsis group and FMT group. The murine model of sepsis was established by intraperitoneal injection of lipopolysaccharide (LPS). After 24 h of LPS injection, the mice in FMT group received FMT from healthy mice. All mice were sacrificed at 48 h after injection of LPS or PBS. The numerical and phenotypic alterations of T cells in lamina propria of intestinal, colon length and the pathological changes in small intestine and colon were detected.

  Results  Compared with the control group, the number of T lymphocytes (22.03% ± 1.50% vs 30.78% ± 1.62%, P<0.01), CD4 ⁺ T cells (15.08% ± 1.01% vs 21.58% ± 1.95%, P<0.01) and CD8 ⁺ T cells (5.05% ± 0.39% vs 6.28% ± 0.21%, P<0.01) in lamina propria of intestinal in sepsis group decreased significantly. The MFIs of CD28 on CD4 ⁺ T cells (227.25 ± 11.47 vs 266.00 ± 6.27, P<0.01) and CD8 ⁺ T cells (73.40 ± 6.82 vs 102.80 ± 4.80, P<0.01) were down-regulated significantly, while the MFI of PD-1 on CD8 ⁺ T cells (19.90 ± 1.47 vs 15.00 ± 2.25, P<0.05) was up-regulated significantly. Colon lengths were significantly shortened (6.90 ± 0.08 cm vs 8.18 ± 0.22 cm, P<0.01), and the small intestine and colon showed obvious inflammation and injury. Compared with the sepsis group, the number of intestinal T cells (26.43% ± 1.86% vs 22.03% ± 1.50%, P<0.05), including CD4 ⁺ T cells (17.48 ± 0.85% vs 15.08% ± 1.01%, P<0.05) and CD8 ⁺ T cells (6.74% ± 0.39% vs 5.05% ± 0.39%, P<0.01) in the fecal bacteria transplantation group increased significantly. The MFIs of CD28 on CD4 ⁺ T cells (252.25 ± 7.14 vs 227.25 ± 11.47, P<0.05) and CD8 ⁺ T cells (95.30 ± 3.63 vs 73.40 ± 6.82, P<0.01) also increased, while the MFI of PD-1 on CD8 ⁺ T cells (17.10 ± 0.52 vs 19.90 ± 1.47, P<0.05) decreased, and the length of colon increased significantly (8.13 ± 0.26 cm vs 6.90 ± 0.08 cm, P<0.01). The inflammation and injury of small intestine and colon were significantly relieved.

  Conclusion  The immune status and homeostasis of intestinal T cells are partly restored, and intestinal inflammation and injury are significantly alleviated by FMT treatment in septic mice.