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Why can pneumonia increase the proportion of neutrophilic leukocytes?

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blood analysis The physical and chemical properties of a sample of blood are examined during blood analysis. The examination of blood is important for the accurate diagnosis of disease.

Pneumonia, particularly when caused by bacteria, frequently leads to an increase in the proportion of neutrophilic leukocytes—a condition known as neutrophilia.12

This occurs because neutrophils are primary mediators of the immune response against infectious microorganisms, such as the bacteria that commonly cause pneumonia. When an infection occurs, the body initiates an inflammatory response, and substances released at the site of tissue damage trigger chemotaxis, signaling neutrophils to migrate from the blood vessels into the infected lung tissue to engulf and destroy the invading bacteria through phagocytosis.13

To support this defense and prevent the rapid depletion of these short-lived cells, the bone marrow mobilizes its large reserve of neutrophils into the bloodstream. Consequently, the circulating count of these white blood cells rises significantly as the body works to combat the infection.13