Circulating exosomes in sepsis induce PD-1 expression in macrophages and promote Th17 differentiation

Area of Science:

• Immunology
• Cell Biology
• Molecular Medicine

Background:

• Sepsis triggers complex immune responses, but the role of circulating exosomes in modulating macrophage and T cell functions is unclear.
• This study investigates how exosomes from septic conditions influence macrophage behavior and subsequent T cell differentiation.

Purpose of the Study:

• To determine the impact of sepsis-derived exosomes on macrophage characteristics, including proliferation, polarization, and phagocytosis.
• To analyze the effect of these exosomes on T cell differentiation, particularly towards the Th17 subtype.

Main Methods:

• A cecal ligation and puncture (CLP) model was used to induce sepsis in mice.
• Exosomes were isolated from septic (CLP-exo) and control (Control-exo) mice blood.
• In vitro assays assessed macrophage function, while co-culture and in vivo studies evaluated T cell responses.

Main Results:

• Sepsis-derived exosomes inhibited macrophage proliferation, induced apoptosis, and suppressed M2 polarization.
• Impaired phagocytic function and increased PD-1 expression were observed in macrophages treated with CLP-exo.
• Co-culture revealed KLF4 pathway activation and increased Th17 cytokine expression; in vivo studies confirmed enhanced Th17 differentiation linked to PD-1.

Conclusions:

• Sepsis-derived exosomes induce PD-1 expression on macrophages, promoting Th17 cell differentiation.
• This identifies a novel mechanism contributing to immune dysregulation in sepsis pathophysiology.
• Findings offer new perspectives on sepsis-related immune system imbalances.