Mast Cells- Derived from bone marrow (CD34+ cells), often in perivascular spaces
- Contain proinflammatory and vasoactive mediators; play important role in wound healing, allergy, anaphylaxis, urticaria, and angioedema (Tables 1-14, 1-15)
- Mast cell proliferation dependent on ligand for c-kit receptor (syn: steel factor, mast cell growth factor, stem cell factor); c-kit encodes a tyrosine kinase receptor and an activating mutation in c-kit proto-oncogene can be associated with childhood and adult-onset mastocytosis
- All mast cells express high affinity receptors for IgE (FcεRI) on their surface; cross-linking of receptor-bound IgE results in release of mast cell granule contents (preformed or newly formed)
- Of note, patients with chronic urticaria may have circulating antibodies to FcεRI on mast cell surface
| | | | | | | Table 1-14 Mast Cell Mediators | | | Mediator | | Function | | Preformed Mediators | | | Histamine | | Vasodilatation, smooth muscle contraction, increased vasopermeability | | | Heparin (Proteoglycan) | | Anticoagulant, anti-complement activity, regulate activity of other mediators | | | Tryptase | | Serine protease | | | Chymase | | Serine protease | | | Carboxypeptidase-A | | Protease | | | Cathepsin G | | Protease | | Newly-Formed Mediators | | | Prostaglandin D2 (PGD2) | | Smooth muscle contraction | | | Leukotrienes (LTC4, LTD4, LTE4) | | Lipid mediators | | | Platelet-activating factor (PAF) | | Vasconstriction, platelet aggregation, smooth muscle contraction, chemotaxis for eosinophils and neutrophils | | | Cytokines | | | Either preformed or newly-formed: TNFα, IL-3, IL-4, IL-5, IL-6, IL-8, IL-13 | | | | | | | |
| | | | | | | | | Of note, PGE2 has inhibitory effect on mast cell degranulation | | | | | | | | |
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| | | | | | | Table 1-15 Triggers for Mast Cell Degranulation | | Mast Cell Degranulating Stimuli | | | Specific antigens (which result in bridging of FcεRI) | | | Anti-FcεRI autoantibodies | | | IL-3 | | | Stem cell factor (SCF) | | | C3a, C4a, C5a (anaphylatoxin) | | | Drugs: NSAIDs, opiates, aspirin, vancomycin, polymyxin B, curare | | | Radiocontrast media | | | Some neuropeptides (i.e., substance P) | | | |
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