Expression of a-tryptase and b-tryptase by human basophils

Background: a and b-Tryptase levels in serum are clinical tools for the evaluation of systemic anaphylaxis and systemic mastocytosis. Basophils and mast cells are known to produce these proteins. Objective: The current study examines the effect of the a,b-tryptase genotype on basophil tryptase levels and the type of tryptase stored in these cells. Methods: Tryptase extracted from purified peripheral blood basophils from 20 subjects was examined by using ELISAs measuring mature and total tryptase and by using an enzymatic assay with tosyl-Gly-Pro-Lys-p-nitroanilide. Tryptase genotypes (4:0, 3:1, and 2:2 b/a ratios) were assessed by using a hot-stop PCR technique with a,b-tryptaseespecific primers. Total a,b-tryptase mRNA was measured by means of competitive RT-PCR, and ratios of a to b-tryptase mRNAwere measured by means of hot-stop RT-PCR. Results: Tryptase in all but one of the basophil preparations was mature and enzymatically active. Tryptase quantities in basophils were less than 1% of those in tissue mast cells. Tryptase genotypes (b/a) among the 20 donors were 4:0 in 7, 3:1 in 7, and 2:2 in 6. Tryptase protein and mRNA levels per basophil were not affected by the tryptase genotype. Conclusion: Basophils from healthy subjects contain modest amounts of mature and enzymatically active tryptase unaffected by the tryptase genotype. (J Allergy Clin Immunol 2004;113:1086-92.) Tryptase is normally expressed by both human mast cells and basophils. In lung- and skin-derived mast cells, mean tryptase levels of 11 and 35 pg per mast cell account for a substantial portion of the cell protein. 1 In contrast,