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Siglec-F+ neutrophils in the spleen induce immunosuppression following acute infection

ABSTRACT: The mechanisms underlying the increased mortality of secondary infections during the immunosuppressive phase of sepsis remain elusive. We established a mouse model of sepsis-induced immunosuppression followed by secondary infection. Compared to other organs, we observed a significant reduction in pro-inflammatory cytokines in the spleen, accompanied by a marked increase in IL-10 production, primarily by infiltrating neutrophils. Furthermore, we confirmed that these infiltrating neutrophils in the spleen during the immunosuppressive phase of sepsis undergo phenotypic change in the local microenvironment, exhibiting high expression of neutrophil biomarkers such as Siglec-F, Ly6G, and Siglec-E. These neutrophils subsequently produced IL-10 to suppress T lymphocytes. Depletion of neutrophils or specifically targeting Siglec-F leads to a notable improvement in the survival of mice with secondary infections. The identification of Siglec-F+ neutrophils as key regulators of immunosuppression following sepsis represents a novel finding with potential therapeutic implications.

ORGANISM(S): Mus musculus

PROVIDER: GSE264139 | GEO | 2024/04/24

REPOSITORIES: GEO

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Project description:Our experiments examined T-lymphocyte numbers and effector-functions in peritoneal contamination and infection (PCI) a mouse model of sepsis. One of our main questions was how T-lymphocytes reconstitute after sepsis-induced lymphopenia. We investigated the quantitative and qualitative recovery of T lymphocytes for 3.5 months after sepsis with or without IL-7 treatment. Sepsis is an immunological dysfunction against pathogens leading to inflammation with massive cytokine production. Simultaneously immunosuppression occurs e.g. lymphopenia, which is a hallmark of sepsis. The resulting immunosuppression is associated with secondary infections, which are often lethal. Moreover sepsis-survivors are burdened with increased morbidity and mortality for several years after the sepsis episode. The duration and clinical consequences of sepsis induced-immunosuppression are currently unknown. More than 50% of T-cells undergo apoptosis shortly after sepsis-induction. However, 8 days after sepsis onset, surviving mice present normal lymphocyte counts. Theoretically, T-cells could reconstitute in two different ways. Firstly, the diminished pool of T-cells is replenished by newly in thymus produced T-cells with new diverse T-cell-receptors (TCRs). Alternatively, remaining T-cells start to proliferate until reaching normal cell count. If this was the case all divided cells shared the same TCRs as primary cells. This could lead to a narrowed TCR diversity within a quantitative normalized T-cell pool and would be an explanation for the long-lasting immune incompetence. To address the question how T-cells recover from lymphopenia we applied next generation sequencing (NGS) to analyse TCR diversity in septic and healthy mice. One group of septic mice received Interleukin-7 (IL-7), an interleukin which regulates T-cell homeostasis and is a promising therapeutically approach for septic patients. 50000 sequences per mouse were analyzed and the three different groups (controls, sepsis, sepsis + IL-7 treatment) compared regarding their diversity. The sequenced raw data (fastq) are uploaded in this library.

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Siglec-F+ neutrophils in the spleen induce immunosuppression following acute infection

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