Tryptase and histamine release due to a sting challenge in bee venom allergic patients treated successfully or unsuccessfully with hyposensitization

Background. Hyposensitization with bee venom leads to full protection in most, but not all patients with IgE-mediated systemic reactions to bee stings. Objective. To determine the relationship of clinical reactivity to the release of mediators and to changes of antibody concentrations in the peripheral circulation at a bee sting challenge test. Methods. Blood was sampled before (0 min) and at 15, 60 and 180 min after a sting challenge from 19 patients on hyposensitization. Of these, six still reacted and 13 were protected. Histamine, mast cell tryptase, bee venom-specific IgE and IgG in the Serum, and histamine release from peripheral blood leucocytes (PBL) upon exposure to bee venom were determined. Results. Tryptase above the detection level was found only at 15 (60)min in 4/6 (1/6) patients who reacted. After the sting challenge there was a significant increase of the histamine levels in patients who reacted at 15 min (P < 0.05) and in patients who did react at 60 and 180 min (P < 0.01). The total histamine content of PBL was significantly decreased after 15 and 60 min in patients who reacted (P < 0.01) and in those that did not (P < 0.05). Bee venom-induced histamine release was significantly reduced in patients reacting and those that did not at 15 min (P < 0.05), and was significantly decreased in reactors also at 60 and 180 min (P < 0.05/0.01). Specific IgG antibodies showed a minor decrease (P < 0.05) after the sting challenge in both groups, whereas specific IgE did not change significantly. Conclusion. These results indicate that bee venom anaphylaxis is associated with the release of mediators from both mast cells as well as basophils. Successful hyposensitization does not induce a state of immunological non-reactivity, but rather alters the magnitude and the pattern of mediator release.