Immune System: Layered Defense to Disorders

Immune system overview and purpose

The immune system is a network of biological systems that protects an organism from disease. It detects and responds to a wide range of threats—including pathogens like viruses, bacteria, and parasites, as well as cancer cells and foreign objects—by distinguishing them from the organism’s own healthy tissues (“self” vs “non-self”). Most organisms rely on layered defenses. Physical and chemical barriers help prevent entry of microbes, and if pathogens breach these barriers, the immune system responds through two major subsystems: innate immunity and adaptive immunity. Innate immunity provides a rapid, non-specific response, while adaptive immunity is antigen-specific and improves with exposure by learning to recognize previously encountered molecules, creating immunological memory. Dysfunction of this system can lead to disorders such as immunodeficiencies, autoimmunity, and hypersensitivity.

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Layered defense: barriers, innate, adaptive

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