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Macrophage

Macrophage

A macrophage is a type of immune cell. It destroys foreign substances to protect the body from infection.

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Macrophages do not travel through the blood. Instead, they remain in one part of the body, within specific tissues.

Macrophages are found in many organs and tissues, including the:

• Brain
• Breast tissue
• Liver
• Lung
• Lymph nodes
• Placenta
• Spleen
• Tonsils

Macrophages quickly recognize infectious material (pathogens), and are an important first line of defense for the immune system. Macrophages take in viruses and bacteria, present them to other cells of the immune system (T and B cells) and activate the immune response.

In people with a disease called Langerhans cell histiocytosis (previously called histiocytosis X), there is an excess of macrophages and other white blood cells in some bodily tissues.

Related Information

References

Crow MK. The innate and adaptive immune systems. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 35.

Hall JE, Hall ME. Resistance of the body to infection: I. Leukocytes, granulocytes, the monocyte-macrophage system, and inflammation. In: Hall JE, Hall ME, eds. Guyton and Hall Textbook of Medical Physiology. 15th ed. Philadelphia, PA: Elsevier; 2026:chap 34.

Review Date: 1/10/2026  

Reviewed By: Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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