Nephrocytes Remove Microbiota-Derived Peptidoglycan from Systemic Circulation to Maintain Immune Homeostasis

Area of Science:

• Immunology
• Renal Physiology
• Microbiology

Background:

• Aberrant immune responses to gut microbiota threaten host health.
• Microbiota-derived molecules, like peptidoglycan, can enter systemic circulation.
• Nephrocytes are key cells for filtering hemolymph in Drosophila.

Purpose of the Study:

• To investigate the role of hemolymph filtration in regulating systemic immune responses to microbiota-derived peptidoglycan.
• To understand the function of nephrocytes in maintaining immune homeostasis.

Main Methods:

• Utilized Drosophila melanogaster model with Klf15 deficiency (Klf15^NN), lacking nephrocytes.
• Compared immune responses and lifespan between Klf15^NN and wild-type (WT) flies.
• Assessed peptidoglycan levels and Toll pathway activation.

Main Results:

• Klf15^NN flies exhibited enhanced resistance to infection but a shortened lifespan.
• Excess circulating peptidoglycan and constitutive Toll pathway activation were observed in Klf15^NN flies.
• WT flies effectively removed peptidoglycan via nephrocyte endocytosis and degradation.

Conclusions:

• Nephrocytes are crucial for filtering microbiota-derived peptidoglycan, preventing immune overactivation.
• Renal filtration maintains immune homeostasis in Drosophila, a function potentially conserved in mammals.
• Impaired renal filtration may contribute to chronic immune activation in disease states.