Immune System
The body's defense network against infection and disease.
Definition
The immune system is a complex network of cells, tissues, and organs that defends the body against infections and other threats. It distinguishes the body's own cells from foreign invaders, but when this process misfires it can trigger autoimmune disease. Understanding it is central to understanding many chronic illnesses.
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Sources & References
This page draws on trusted, authoritative health resources. For medical decisions, always consult a qualified healthcare professional.
- Patient Engagement & Hormone HealthEndocrine SocietyProfessional Medical Society
- Health InformationNational Institutes of Health (NIH)Government Health Agency
- Health Topics: Trusted Consumer Health InformationMedlinePlus, U.S. National Library of MedicineGovernment Health Agency
- Health Topics A-ZMedlinePlus, U.S. National Library of MedicineGovernment Health Agency
- Health Library: Diseases & ConditionsCleveland ClinicAcademic Medical Center
Content Review
- Last Reviewed
- July 2026
- Last Updated
- July 2026
- Content Type
- Educational Documentary Companion
- Evidence Standard
- Evidence-Informed
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