Types of tryptases:
(1) alpha (released by all mast cells)
(2) beta (released following mast cell activation)
(3) gamma (released from the mast cell but it remains attached to the mast cell surface)
Total serum tryptase levels reflect circulating forms of alpha and beta tryptases plus their pro-enzymes. It reflects the total number of mast cells The total serum tryptase level is elevated in systemic mastocytosis (>=2 times the upper limit of the normal reference range)..
Beta tryptase is released following mast cell activation along with histamine. An elevated beta-tryptase level is a marker of anaphylaxis that can be detected for a few hours after the event (while histamine levels return to normal within an hour).
The half-life of beta-tryptase is about 2 hours. A blood sample collected from 30 minutes to 4 hours after the event should be able to detect any elevation.
Situations in which the measured serum beta-lactamase may not be elevated in an apparent case of anaphylaxis:
(1) the blood sample was drawn too early (it may take 30 minutes after the exposure before there is a rise in serum levels)
(2) the blood sample was drawn too late after the exposure
(3) pseudo-anaphylaxis due to absorption of histamine in scombroid fish poisoning
(4) activation of mast cells was limited to mast cells in the gastrointestinal tract
