A parulis is actively draining pus. Which cell type would predominate in the exudate?

Correct answer: A. Neutrophils

• A. CORRECT. Pus is, by definition, a collection of NEUTROPHILS (polymorphonuclear leukocytes) together with liquefied necrotic tissue and bacteria. A draining parulis is the stoma of an ACUTE suppurative process, and the neutrophil is the first responder and dominant cell of acute inflammation.
• B. Macrophages dominate in CHRONIC inflammation and in granulomatous disease. They appear later, clearing debris after the acute phase.
• C. Basophils are rare circulating granulocytes involved in allergic and hypersensitivity responses. They are not a feature of pyogenic infection.
• D. Plasma cells are antibody-producing B-cell derivatives characteristic of CHRONIC inflammation — abundant in a periapical granuloma, but not in acute pus.

Note: Contrast the histology: acute abscess = neutrophils; periapical granuloma = lymphocytes, plasma cells and macrophages; periapical cyst = the same chronic infiltrate plus a stratified squamous epithelial lining.