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Which white blood cells are usually the first to reach a site of infection?

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Illustration of a blood vessel with a cutaway view showing red blood cells, white blood cells, platelets, and plasma, each labeled to highlight the main components of blood. — white blood cell Blood is made up of multiple components, including red blood cells, white blood cells, platelets, and water-rich plasma.

Neutrophils are typically the first white blood cells to arrive at a site of infection or tissue injury.12

These cells, which make up 50 to 80 percent of all white blood cells, are rapidly mobilized from the bone marrow in response to inflammation or infection. Guided by a process called chemotaxis—where they follow chemical signals released at the site of damage—neutrophils can reach the area within an hour. Once there, they act as voracious phagocytes, engulfing and destroying microorganisms using potent enzymes stored in their granules.3214

Other white blood cells, such as monocytes (which mature into macrophages), eosinophils, and basophils, typically arrive at the site later than neutrophils.12