Immune system defenses and dysfunction

Immune system overview and protective role

The immune system is a network of biological systems that protects an organism from disease by detecting and responding to pathogens (such as viruses, bacteria, and parasites), cancer cells, and foreign objects, while distinguishing them from the body’s own healthy tissue. Nearly all organisms have some form of immune defense, and many species use two major subsystems: innate immunity, which provides a rapid, preconfigured response to broad threats, and adaptive immunity, which tailors responses to specific antigens through learning and generates immunological memory. Protection occurs through layered defenses. Physical barriers (like skin and mucous membranes) help prevent entry of microbes, and if pathogens breach these barriers, the innate immune system responds immediately in a non-specific way. If needed, the adaptive immune system is activated and mounts antigen-specific attacks; after the threat is cleared, memory cells enable faster and stronger responses upon re-exposure. When immune regulation fails, protective roles can be disrupted, leading to immune-related diseases such as immunodeficiency (increased infections), autoimmunity (attack on self tissues), and inflammatory or cancer-related problems.

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Innate immune system versus adaptive immune system

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