Atezolizumab alleviates the immunosuppression induced by PD‑L1‑positive neutrophils and improves the survival of mice during sepsis.

Atezolizumab can reduce immunosuppression caused by T lymphocyte apoptosis in various cancer types. The current study aimed to investigate whether this drug can also alleviate immunosuppression during sepsis. For that purpose, a C57BL/6 mouse sepsis model was generated. Mice were randomly assigned to three groups: Sham, cecal ligation and puncture (CLP) and atezolizumab groups. Atezolizumab was administered <em>in vivo</em> by intraperitoneal injection. The expression of programmed death ligand‑1 (PD‑L1) on neutrophils and programmed death‑1 (PD‑1) on T lymphocytes was evaluated, and endotoxin concentration, intestinal permeability, ileum histopathological score and tight junction protein expression were assessed to determine the extent of disease in each group. The rate of T lymphocyte apoptosis was determined to assess the effects of atezolizumab on T lymphocyte apoptosis <em>in vivo</em> and <em>in vitro</em>. Survival times were also recorded to compare mouse prognosis during sepsis. In the CLP group, the proportion of PD‑L1+ neutrophils was significantly higher at 48, 72 and 96 h in blood, and at 24, 48, 72 and 96 h in bone marrow, compared with those of the sham group (P&lt;0.05). The proportion of PD‑1+ T lymphocytes was also upregulated at 72 h in blood. In the atezolizumab group, endotoxin concentration, intestinal permeability and ileum histopathological score were lower compared with those in the CLP group (P&lt;0.05), whereas the expression of claudin‑1 and occludin proteins on ileum was higher compared with that in the CLP group (P&lt;0.05). Both <em>in vivo</em> and <em>in vitro</em> experiments indicated that the rate of T lymphocyte apoptosis following atezolizumab treatment was lower compared with that in the CLP group (P&lt;0.05). Survival analysis demonstrated that mice in the atezolizumab group survived longer compared with those in the CLP group (P&lt;0.05). The current study demonstrated that treatment with atezolizumab may be an effective method for treating immunosuppression induced by sepsis.