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Why can bacterial infections increase the proportion of band neutrophils in the blood?
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blood disease
Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.
Bacterial infections trigger an increase in band neutrophils—immature forms of neutrophils—due to the body's urgent need to combat extensive tissue damage or infection.1
Normally, the bone marrow produces mature neutrophils over the course of about one week. However, when an infection is severe, the body rapidly depletes its circulating supply of mature cells as they migrate to the site of injury via chemotaxis. To compensate for this rapid depletion and ensure an adequate immune response, the bone marrow mobilizes and releases its reserve stores of neutrophils into the blood. Because these reserves include cells that have not yet fully matured, the proportion of band neutrophils in the bloodstream rises significantly.21