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Shielded by the Dead: How Killed Bacteria Shape the Dynamics and Evolution of Innate Immunity
Stephen P Ellner1,2, Nicolas Buchon3,2, Tobias Dörr4,2,5
1Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853.
The American Naturalist
|July 23, 2026
Summary
Bacterial corpses can hinder infection control by sequestering immune effectors. However, this "sponginess" also protects against autoimmune damage, influencing immune system evolution.
Area of Science:
- Immunology
- Microbial Pathogenesis
- Mathematical Biology
Background:
- Infection outcomes depend on host immunity and microbial dynamics.
- Dead bacteria (corpses) can sequester immune effectors, impacting infection.
- The role of bacterial corpse "sponginess" in disease dynamics is understudied.
Purpose of the Study:
- To investigate the impact of bacterial corpse sponginess on within-host infection dynamics.
- To model the dual role of corpse sponginess in infection control and autoimmune damage.
- To explore how corpse sponginess influences the evolution of immune response kinetics.
Main Methods:
- Developed a mechanism-based mathematical model for within-host bacterial infection.
- Incorporated host microbial sensing, immune effector production, and immune shutdown.
- Analyzed the effects of immune effector sequestration by bacterial corpses.
Main Results:
- Bacterial corpse sponginess impedes infection control by sequestering immune effectors.
- Corpse sponginess mitigates autoimmune damage by removing circulating immune effectors.
- This dual effect alters the balance between infection-induced damage and autoimmune harm.
Conclusions:
- Bacterial corpse sponginess has a significant, dual impact on infection dynamics.
- It influences the evolutionarily optimal strategies for immune activation and shutdown.
- Understanding corpse sponginess is crucial for comprehending host-pathogen interactions and immune system evolution.
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