Animal Defenses against Infectious Agents: Is Damage Control More Important Than Pathogen Control

摘要

Once an infectious agent is established, hosts can do two things to minimize the agent's impact on their health. Most obviously, they can directly attack the growing pathogen population to contain or eliminate it. But hosts can also attempt to minimize the harm caused by a given number of pathogens, for instance by ramping up tissue repair and detoxifying pathogen by-products. “Resistance” and “tolerance,” as these two types of defense are known in the plant literature, were first distinguished by botanists in the late 1800s [1] and this distinction has been a focus of considerable work by plant scientists since then [2–4]. However, those advances have had a minimal effect on the study of animal diseases. Immunologists, microbiologists, and parasitologists have typically focused on the ability to limit parasite numbers (resistance) or the overall ability to maintain health irrespective of parasite burden (resistance plus tolerance), with little attempt to formally decompose human or animal health into resistance and tolerance components. That situation is only now beginning to change. The early results already have significant experimental and conceptual implications.