Mast cell chymase: a useful serum marker in anaphylaxis

RATIONALE: The reliable diagnosis of anaphylaxis can present challenge. We have explored mast cell chymase as a potential marker for anaphylaxis.METHODS: A sandwich-based ELISA was developed with monoclonal antibodies we have prepared against chymase, and validated for application to serum samples. The enzymatic activity of chymase was determined in parallel using the chromogenic substrates suc-AAPF-pNA and RETF-4NA. Tryptase, carboxypeptidase and DPPI were measured by ELISA. Serum was collected from cases of anaphylaxis provoked by food, drug and insect stings (n=181); from healthy blood donors (n=123); and from patients allergic to food (n=76) or drugs (n=26).RESULTS: The ELISA allowed detection of chymase in all serum samples, and values obtained were unaffected by the presence of alpha-2-macroglobulin or other inhibitors. Chymase levels in serum collected from patients within 8h of anaphylaxis were greater than those in the control group (p=0.0069); and concentrations remained high at least 24h after onset of the reaction. Chymase levels in anaphylaxis correlated with levels of mast cell carboxypeptidase and with dipeptidyl peptidase 1 (DPPI), but not tryptase. Concentrations of chymase measured by ELISA were weakly associated with serum chymase activity. Addition of DPPI to serum increased the chymase activity in samples collected prior to allergen challenge (p=0.0008) consistent with the presence of pro-forms of chymase in the circulation. However, DPPI-induced increases in serum chymase activity were not observed in samples collected following a reaction (when serum DPPI concentrations were elevated).CONCLUSIONS: Measurement of mast cell chymase in serum should be useful as a means for laboratory confirmation of anaphylaxis

IgE-mediated food allergy diagnosis: Current status and new perspectives

In June 2005, the work of the EU Integrated Project EuroPrevall was started. EuroPrevall is the largest research project on food allergy ever performed in Europe. Major aims of the project are to generate for the first time reliable data on the prevalence of food allergies across Europe and on the natural course of food allergy development in infants. Improvement of in vitro diagnosis of food allergies is another important aim of the project. The present review summarizes current knowledge about the clinical presentation of food allergy and critically reviews available diagnostic tools at the beginning of the project period. A major problem in diagnosis is a relatively poor ,clinical specificity', i. e. both positive skin tests and in vitro tests for specific IgE are frequent in sensitized subjects without food allergy symptoms. So far, no in vitro test reliably predicts clinical food allergy. EuroPrevall aims at improving the predictive value of such tests by proceeding from diagnosis based on allergen extracts to purified allergen molecules, taking into account the affinity of the IgE-allergen interaction, and evaluating the potential of biological in vitro tests such as histamine release tests or basophil activation tests including assays performed with permanently growing cell lines. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA