Study note
PathologyInflammation and Repair

Fever, inflammatory leukocytosis, and granulomatous reactions

THE CONTEXT
Systemic inflammatory responses include fever and changes in circulating leukocytes. The target passage also describes granulomatous findings in tuberculosis and leprosy.

Fever and its suppression

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Prostaglandin E2 elevates body temperature by altering neuronal firing in the preoptic nucleus of the hypothalamus.
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Nonsteroidal anti-inflammatory drugs, including aspirin, reduce fever by inhibiting prostaglandin synthesis.
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A protective role for fever has been proposed, but its underlying mechanism is unknown.

Leukocytosis and leukemoid reactions

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Leukocytosis is common in inflammatory reactions, particularly bacterial infections. The leukocyte count usually rises to 15,000 or 20,000 cells/mL.
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Extreme elevations of 40,000–100,000 cells/mL are called leukemoid reactions. They resemble leukemic white cell counts and must be distinguished from leukemia.
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The initial leukocytosis results from accelerated release of cells from the bone marrow postmitotic reserve pool, stimulated by cytokines including TNF and IL-1.
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An increased number of immature neutrophils, or band cells, in the blood is called a shift to the left.
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Prolonged infection increases leukocyte production through colony stimulating factors released by macrophages, stromal cells, endothelial cells, and T lymphocytes in the marrow.

Patterns of leukocyte elevation

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Most bacterial infections increase the circulating neutrophil count, producing neutrophilia.
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Viral infections such as infectious mononucleosis, mumps, and German measles cause an absolute increase in lymphocytes.

Granulomatous morphology

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A typical tuberculous granuloma has central necrosis surrounded by multinucleate giant cells, epithelioid cells, and lymphocytes.
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Tuberculosis is caused by Mycobacterium tuberculosis infection. Its caseating granulomas contain activated macrophages called epithelioid cells, peripheral fibroblasts and lymphocytes, occasional Langhans giant cells, and central necrosis with amorphous granular debris; acid-fast bacilli are present.
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Leprosy is caused by Mycobacterium leprae infection and is associated with acid-fast bacilli in macrophages and noncaseating granulomas.
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