[Basophil degranulation test (BDT) as a parameter of hyposensitization with Hymenoptera venoms]

In a population of 24 insect sting allergy patients undergoing venom immunotherapy the basophil degranulation test (BDT) in the patient sera ("unwashed" BDT) and with washed leukocytes ("washed" BDT) after incubation with bee and wasp (yellow jacket) venom was performed before and during treatment. Venom specific IgE and IgG antibodies, detected by means of RAST, were also monitored. The "unwashed" BDT usually became negative within 6-9 months of beginning immunotherapy, whereas the IgE-RAST was still clearly positive. This was attributed to the blocking influence of the venom specific IgG antibodies induced by the venom therapy. In fact, at this time the BDT with "washed" blood leukocytes, i.e. after elimination of the serum antibodies, was generally still positive. Only during further immunotherapy did cellular sensitization in the "washed" BDT gradually disappear, whereas the IgE-RAST usually turned out weakly positive. A third of the patients showed simultaneously negative results of "unwashed" and "washed" BDT, independently of venom specific IgE and IgG levels. These findings suggest a specific reactivity change of the blood basophils (cellular desensitization) induced by the immunotherapy. The BDT can be used as an immunological parameter for IgG-monitoring of the course of venom immunotherapy and--in addition to skin tests and IgE-RAST--as a further criterion for deciding to stop venom therapy if it turns negative with the washed cells.