The article discusses the concept of disease tolerance as a defense strategy in the immune system, which is distinct from resistance. Disease tolerance refers to the host's ability to reduce the negative impact of infections on its fitness without directly eliminating the pathogen. This strategy has been largely overlooked in animal and human studies. The immune system traditionally focuses on detecting and eliminating pathogens, but disease tolerance involves mechanisms that protect the host from the harmful effects of infection, such as tissue damage and immunopathology. Disease tolerance can be achieved through various mechanisms, including avoidance of pathogens, reduction of pathogen burden, and minimizing the damage caused by the immune response. The article highlights that tolerance mechanisms can be induced by the host's own stress responses, such as the unfolded protein response, and can be influenced by factors like tissue repair capacity, functional autonomy of cells, and the environment. Tolerance is not limited to infection but can apply to various diseases, including autoimmune conditions. The article also discusses how tolerance can be affected by age, with both young and old individuals often being more susceptible to infections. Additionally, the role of tolerance in the context of immunodeficiencies and the importance of identifying tolerance mechanisms for therapeutic approaches is emphasized. The study of disease tolerance is crucial for understanding infectious diseases and developing new treatments. It suggests that enhancing tolerance mechanisms can reduce morbidity and mortality associated with infections, especially in cases where the immune system is ineffective or causes excessive damage. The article concludes that tolerance is a complex and multifaceted strategy that plays a vital role in host survival and disease resistance.The article discusses the concept of disease tolerance as a defense strategy in the immune system, which is distinct from resistance. Disease tolerance refers to the host's ability to reduce the negative impact of infections on its fitness without directly eliminating the pathogen. This strategy has been largely overlooked in animal and human studies. The immune system traditionally focuses on detecting and eliminating pathogens, but disease tolerance involves mechanisms that protect the host from the harmful effects of infection, such as tissue damage and immunopathology. Disease tolerance can be achieved through various mechanisms, including avoidance of pathogens, reduction of pathogen burden, and minimizing the damage caused by the immune response. The article highlights that tolerance mechanisms can be induced by the host's own stress responses, such as the unfolded protein response, and can be influenced by factors like tissue repair capacity, functional autonomy of cells, and the environment. Tolerance is not limited to infection but can apply to various diseases, including autoimmune conditions. The article also discusses how tolerance can be affected by age, with both young and old individuals often being more susceptible to infections. Additionally, the role of tolerance in the context of immunodeficiencies and the importance of identifying tolerance mechanisms for therapeutic approaches is emphasized. The study of disease tolerance is crucial for understanding infectious diseases and developing new treatments. It suggests that enhancing tolerance mechanisms can reduce morbidity and mortality associated with infections, especially in cases where the immune system is ineffective or causes excessive damage. The article concludes that tolerance is a complex and multifaceted strategy that plays a vital role in host survival and disease resistance.