Mast cells

Mast cells are tissue-resident granulocytes found near blood vessels and nerves, particularly in skin, lungs, and gut mucosa. They store pre-formed inflammatory mediators (histamine, tryptase, heparin) in their granules. They are central effectors in IgE-mediated allergic reactions (anaphylaxis, hay fever) and defense against parasites. Upon activation, they rapidly degranulate and also synthesize cytokines/chemokines, influencing inflammation, immunity, and even tissue remodeling.