Molecules that instigate inflammation during an immune response. Mast cells secrete leukotrienes in response to stimulation by immunoglobulin E (IgE). Leukotrienes are derived from arachidonic acid, which is the same base source (precursor) as that of prostaglandins, the other primary agents of inflammation.
The actions of leukotrienes are most apparent in asthma, in which they cause the bronchioles (tiny bronchi deep within the lungs) to constrict. Leukotriene release becomes more rapid with each hypersensitivity reaction.
Leukotrienes also attract eosinophils, which cause swelling in the bronchial mucosa (mucous membrane lining of the bronchi). In inflammatory responses outside the pulmonary system, leukotrienes attract neutrophils with similar effect (swelling and discomfort). Eosinophils and neutrophils are types of granulocytes.
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