DEVELOPMENT OF A NEW, MORE SENSITIVE IMMUNOASSAY FOR HUMAN TRYPTASE -USE IN SYSTEMIC-ANAPHYLAXIS

Tryptase, a neutral protease, is selectively concentrated in the secre tory granules of human mast cells, and its release into the circulatio n serves as a clinical marker of mast cell activation. The current stu dy describes a new, more sensitive ELISA utilizing a newly developed, mouse monoclonal IgG1 antibody for capture called B12 and capable of d etecting tryptase in normal plasma and serum. The greater sensitivity of the new immunoassay results in part from a greater portion of trypt ase being detected. Mean levels of tryptase in serum from normal subje cts from Richmond, Virginia (4.9 ng/ml; n = 56), Munich, Germany (3.8 ng/ml; n = 19), and Amersfoort, The Netherlands (1.9 ng/ml; n = 8) wer e as indicated. In 62 subjects with ongoing allergic rhinitis, tryptas e levels were no different in serum than for 19 normal controls, indic ating that local mast cell activation is not necessarily reflected in the circulation. In 61 subjects sensitive to honey bee or yellow jacke t venom by history, the 17 destined to have a severe, hypotensive resp onse to a sting challenge had higher levels of tryptase at baseline th an mild reactors, nonreactors, and controls, suggesting that baseline levels of tryptase may predict the severity of the clinical response t o allergen in sensitive subjects.