Mast Cells: Key Mediators of Inflammation and Allergy

Mast cells are tissue-resident granulocytes derived from hematopoietic stem cells. They reside near blood vessels, nerves, and mucosal surfaces (skin, respiratory, GI tracts).

Upon activation (IgE-mediated allergy, complement, neuropeptides, TLR ligands, physical stimuli), they degranulate, releasing preformed mediators:

• Histamine: Vasodilation, increased permeability, bronchoconstriction, itching.
• Heparin: Anticoagulant.
• Serotonin: Vasoconstriction, smooth muscle contraction (prominent in rodents).
• Proteases (tryptase, chymase): Tissue remodeling, matrix degradation.

They also synthesize de novo lipid mediators (prostaglandins, leukotrienes) and cytokines (TNF-α, IL-4, IL-6, IL-13) amplifying inflammation and recruiting immune cells.

Central to allergic reactions (anaphylaxis, asthma, urticaria), host defense (parasites, bacteria), and chronic inflammatory diseases.