Evolutionary Causes and Consequences of Immunopathology

TLDR

Immune responses can cause severe disease, and immunopathology is a common cause that strongly impacts host and parasite fitness. The authors review two major mechanistic causes of immunopathology in mammals, propose hypotheses for why natural selection has not eliminated it, and suggest how this double‑edged sword may shape parasite virulence and host resistance evolution. The review examines two main mechanistic causes of immunopathology in mammals and their influence on immune system design.

Abstract

▪ Abstract Immune responses can cause severe disease, despite the role immunity plays in defending against parasitism. Indeed, immunopathology is a remarkably common cause of disease and has strong impacts upon both host and parasite fitness. Why has immune-mediated disease not been eliminated by natural selection? What constraints might immunopathology impose upon the evolution of resistance? In this review, we explore two major mechanistic causes of immunopathology in mammals and consider how such disease may have influenced immune system design. We then propose hypotheses that could explain the failure of natural selection to eliminate immunopathology. Finally, we suggest how the evolution of strategies for parasite virulence and host resistance may be shaped by this “double-edged sword” of immunity. Future work may reveal whether immunopathology constrains the evolution of resistance in all host taxa.