The release of histamine is associated with the inactivation of mast cell chymase during immediate allergic wheal reaction in the skin

Background Chymase released by mast cells can participate in the immediate allergic wheal. However, chymase may be susceptible to inactivation by protease inhibitors during degranulation. Objective To study the inactivation of chymase and the release of histamine in the immediate allergic wheal reaction. Methods Ten sensitive atopic subjects were prick‐tested with the cow dander allergen, and skin biopsies were taken from the control skin and from the challenge site at 30 and 120 min. Tryptase (Tact) and chymase (Cact) activities in mast cells were measured enzyme‐histochemically. Sequential double‐staining was used to demonstrate the activity and immunoreactivity (Cprot) of chymase in the same mast cell as well as α1‐proteinase inhibitor (α1‐PI) and α1‐antichymotrypsin (α1‐AC) in Tact+ cells. Skin microdialysis was used to monitor histamine release after the allergen challenge for up to 120 min Results The numbers of Tact+ and Cact+ cells were already maximally decreased at 30 min by 37 ± 17% and 61 ± 31%, respectively (mean ± SD, P