Which statement best describes the major action of leukotrienes?

• A. Stimulation of platelet aggregation
• B. Decrease chemotaxis
• C. Vasodilation & ↑capillary permeability, chemotaxis, prolong inflammation due to later effects
• D. Inhibition of vascular permeability

Answer: (C)

Leukotrienes are inflammatory mediators produced from arachidonic acid that amplify the immune response. Their hallmark actions are increasing vascular permeability and promoting chemotaxis, which together sustain and intensify inflammation. The chemotactic effect is especially driven by LTB4, drawing neutrophils to the site, while LTC4 and LTD4 increase the permeability of vessels, contributing to swelling and edema. These effects help explain why leukotrienes are linked to prolonged inflammation and to bronchoconstriction seen in allergic and asthmatic responses.

This makes the statement that best describes their major action the one that includes increasing capillary permeability, chemotaxis, and the prolongation of inflammation over time. The other options misstate their roles: they do not primarily stimulate platelet aggregation, they do not decrease chemotaxis, and they do not inhibit vascular permeability.