Neonatal low-density granulocytes internalize and kill bacteria but suppress monocyte function using extracellular...

Area of Science:

• Immunology
• Neonatal immunology

Background:

• Low-density granulocytes (LDGs) are prevalent in neonatal blood.
• Their role in bacterial infection and interaction with other immune cells is poorly understood.

Purpose of the Study:

• To investigate the function of human neonatal LDGs in controlling bacterial infections.
• To determine how LDGs interact with mononuclear phagocytes during infection.

Main Methods:

• Phagocytosis assays using *Escherichia coli* O1:K1:H7.
• Analysis of bacterial killing and cytokine production.
• Assessment of extracellular DNA (eDNA) release and its effect on monocyte function.

Main Results:

• Neonatal LDGs phagocytose *E. coli* but are less efficient than monocytes.
• LDGs exhibit reduced bacterial killing and lower inflammatory cytokine response compared to monocytes.
• LDG-derived eDNA, while lacking antibacterial activity, impairs monocyte-mediated bacterial control.

Conclusions:

• LDG recruitment to infection sites may hinder neonatal host defense.
• LDGs have a distinct inflammatory profile compared to monocytes.
• LDGs employ a novel immunosuppressive mechanism via eDNA release.