Granulocytes are a type of white blood cell that has small granules, which contain proteins. The specific types of granulocytes are neutrophils, eosinophils, and basophils.
Granulocytes, specifically neutrophils, help the body fight bacterial infections. The number of granulocytes in the body usually increases when there is a serious infection. People with a lower number of granulocytes are more likely to develop bad infections more often.
Granulocytes are counted as part of a white blood cell differential test.
Hall JE. Resistance of the body to infection: I. leukocytes, granulocytes, the monocyte-macrophage system, and inflammation. In: Hall JE, ed. Guyton and Hall Textbook of Medical Physiology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 34.