A 37-year-old man comes to the emergency department because of increasing pain and tenderness in his right forearm. During a bar brawl 6 days earlier, he sustained a 4-cm laceration through the skin and subcutaneous tissue of his forearm. Treatment at the time of injury included cleaning and dressing the wound. Physical examination shows erythema surrounding the wound site and expression of yellow pus when pressure is applied adjacent to the wound. Which of the following molecules is most likely responsible for causing accumulation of pus over this patient's wound?

Question

A 37-year-old man comes to the emergency department because of increasing pain and tenderness in his right forearm.  During a bar brawl 6 days earlier, he sustained a 4-cm laceration through the skin and subcutaneous tissue of his forearm.  Treatment at the time of injury included cleaning and dressing the wound.  Physical examination shows erythema surrounding the wound site and expression of yellow pus when pressure is applied adjacent to the wound.  Which of the following molecules is most likely responsible for causing accumulation of pus over this patient's wound?

Quizplus · Accepted Answer

Pus consists of a thin, protein-rich fluid, known as liquor puris, and dead leukocytes, primarily neutrophils. During infection, macrophages and surrounding endothelial cells release cytokines such as interleukin-8 (IL-8) that trigger neutrophils to enter the site of infection via chemotaxis. IL-8 also induces phagocytosis in neutrophils once they have arrived. (Choice A) Bradykinin is a component of the kinin system. It causes vasodilation, increases vascular permeability, stimulates nonvascular smooth muscle contraction, and mediates pain. (Choice B) C3a is a component of the complement system. C3a, C4a, and C5a are inflammatory anaphylatoxins that trigger histamine release from mast cells, resulting in vasodilation and enhanced vascular permeability. C5a also recruits and activates neutrophils, monocytes, eosinophils, and basophils. In contrast, C3a recruits and activates eosinophils and basophils, but not neutrophils. (Choice C) IL-3 is a cytokine produced by activated T cells. It stimulates the growth and differentiation of stem cells in the bone marrow. (Choice E) IL-10 is an anti-inflammatory cytokine produced by T_H2 cells and macrophages. IL-10 limits the production of pro-inflammatory cytokines (eg, gamma interferon, IL-2, IL-3, and TNF-α). (Choice F) Leukotriene C₄ (and its relatives, leukotriene D₄ and E₄) triggers intense vasoconstriction, increased vascular permeability, and bronchospasm. Leukotriene B₄ and the leukotriene precursor 5-HETE stimulate neutrophil migration to the site of inflammation (but not leukotriene C₄). Educational objective: Interleukin-8 is a chemokine produced by macrophages that induces chemotaxis and phagocytosis in neutrophils. Other significant chemotactic agents include leukotriene B₄, 5-HETE (the leukotriene precursor), and complement component C5a.

A 37-Year-Old Man Comes to the Emergency Department Because of Increasing