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from Wikipedia, the free encyclopedia

Immune system

The immune system is the body’s defense network against harmful invaders such as bacteria, viruses, fungi, and parasites. It is made up of a complex collection of cells, tissues, and organs that work together to detect and eliminate threats while distinguishing them from the body’s own healthy cells. This system protects against infections, helps prevent disease, and plays a key role in wound healing and immune surveillance.

Key components of the immune system include white blood cells, such as lymphocytes and phagocytes, which patrol the body for foreign substances. The lymphatic system, spleen, thymus, bone marrow, and lymph nodes all support immune function by producing, storing, or transporting these cells. The skin and mucous membranes serve as physical barriers, while chemical defenses like enzymes in saliva and stomach acid add further protection.

The immune response can be divided into two main types: innate and adaptive. The innate immune system provides a rapid, general defense against pathogens, while the adaptive immune system learns to recognize specific invaders and mount a more targeted response. This adaptive memory allows the body to respond more effectively to repeated exposures and is the basis for how vaccines work.

When functioning properly, the immune system protects the body without attacking its own tissues. However, dysfunction can lead to problems such as autoimmune diseases, immunodeficiencies, or allergies. Research into immunology continues to drive advances in treatments for cancer, infectious diseases, and inflammatory disorders, highlighting the immune system’s central role in health and disease.

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October 18, 2025

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