Mast cell tryptase: a review of its physiology and clinical significance

Summary Mast cells, which are granulocytes found in peripheral tissue, play a central role in inflammatory and immediate allergic reactions. β‐Tryptase is a neutral serine protease and is the most abundant mediator stored in mast cell granules. The release of β‐tryptase from the secretory granules is a characteristic feature of mast cell degranulation. While its biological function has not been fully clarified, mast cell β‐tryptase has an important role in inflammation and serves as a marker of mast cell activation. β‐Tryptase activates the protease activated receptor type 2. It is involved in airway homeostasis, vascular relaxation and contraction, gastrointestinal smooth muscle activity and intestinal transport, and coagulation. Serum mast cell β‐tryptase concentration is increased in anaphylaxis and in other allergic conditions. It is increased in systemic mastocytosis and other haematological conditions. Serum β‐tryptase measurements can be used to distinguish mast cell‐dependent reactions from other systemic disturbances such as cardiogenic shock, which can present with similar clinical manifestations. Increased β‐tryptase levels are highly suggestive of an immunologically mediated reaction but may also occur following direct mast cell activation. Patients with increased mast cell β‐tryptase levels must be investigated for an allergic cause. However, patients without increased mast cell tryptase levels should be investigated if the clinical picture suggests severe anaphylaxis.