Colorized scanning electron micrograph of a natural killer cell from a human donor
The immune system is a network of cells, tissues, and organs that work together to protect the body from infection.
Why Is Immune System Research a Priority for NIAID?
Although scientists have learned much about the immune system, they continue to study how the body targets invading microbes, infected cells, and tumors while ignoring healthy tissues.
How Is NIAID Addressing This Critical Issue?
The combination of new technology and expanded genetic information promises to reveal more about how the body protects itself from disease. In turn, scientists can use this information to develop new strategies for the prevention and treatment of infectious and immune-mediated diseases.
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Features of an Immune Response
An immune response is generally divided into innate and adaptive immunity. Innate immunity occurs immediately, when circulating innate cells recognize a problem. Adaptive immunity occurs later, as it relies on the coordination and expansion of specific adaptive immune cells. Immune memory follows the adaptive response, when mature adaptive cells, highly specific to the original pathogen, are retained for later use.
Immune Cells
Granulocytes include basophils, eosinophils, and neutrophils. Basophils and eosinophils are important for host defense against parasites. They also are involved in allergic reactions. Neutrophils, the most numerous innate immune cell, patrol for problems by circulating in the bloodstream. They can phagocytose, or ingest, bacteria, degrading them inside special compartments called vesicles.
Immune Tolerance
Tolerance is the prevention of an immune response against a particular antigen. For instance, the immune system is generally tolerant of self-antigens, so it does not usually attack the body's own cells, tissues, and organs. However, when tolerance is lost, disorders like autoimmune disease or food allergy may occur.