Individual IL-3 priming is crucial for consistent in vitro activation of donor basophils in patients with chronic urticaria.

BACKGROUND: The in vivo autologous serum skin test (ASST) is the diagnostic gold standard to detect autoantibodies against FcεRI or IgE itself, as well as other autoreactive serum components, in patients with chronic spontaneous urticaria (CU). Coincubation of patient sera with donor basophils and measuring their degranulation in vitro could be a safe alternative but has shown inconsistent results. OBJECTIVE: Optimization of the basophil activation test to detect autoreactive serum components in patients with CU. METHODS: The ability of patient sera to induce CD63 and CD203c in donor basophils (n = 15) was measured by means of flow cytometry. Sera of 20 patients with CU (10 with positive ASST results), 15 patients with cold urticaria, and 27 healthy control subjects were included to optimize test conditions with donor basophils and a basophil cell line (RBL703/21) followed by testing of 110 consecutive patients from clinical routine. RESULTS: We demonstrate that individual IL-3 priming normalized the initially inconsistent basophil reactivity and led to reproducible and comparable test results irrespective of the basophil donors used. CD203c as an activation marker and the use of a basophil cell line were less suitable for this purpose. CONCLUSION: The basophil activation test with individualized IL-3 priming for each basophil donor is a reproducible and reliable alternative to the ASST. There are several advantages over the ASST: no risk of accidental infection, no influence of antihistamines on the test result, quantifiable results, and a potential in providing treatment monitoring. The exact nature of the degranulating factor or factors in patient sera remains an open question.

The complex clinical picture of side effects to biologicals.

Biologicals are proteins used as drugs. Biologicals target clearly defined molecular structures, being part of established pathogenetic pathways. Therefore, their focused mode of action seems to render them superior to classic small molecular drugs regarding "off-target" adverse drug reactions (ADR). Nevertheless, the increasing use of biologicals for the treatment of different diseases has revealed partially unexpected adverse reactions. The often direct interaction of a biological with the immune system provides a clue to most side effects, which have consequently been subclassified, based on pathogenetic principles, into 5 subtypes named alpha, beta, gamma, delta, and epsilon, reflecting overstimulation (high cytokine values, type alpha), hypersensitivity (type beta), immune deviation (including immunodeficiency, type gamma), cross-reactivity (type delta), and nonimmune mediated side effects (type epsilon). This article presents typical clinical manifestations of these subtypes of ADR to biologicals, proposes general rules for treating them, and provides a scheme for a thorough allergological workup. This approach should help in future handling of these often very efficient drugs.

The basophil activation test in immediate-type drug allergy.

Diagnosis of drug allergy involves first the recognition of sometimes unusual symptoms as drug allergy and, second, the identification of the eliciting drug. This is an often difficult task, as the clinical picture and underlying pathomechanisms are heterogeneous. In clinical routine, physicians frequently have to rely upon a suggestive history and eventual provocation tests, both having their specific limitations. For this reason both in vivo (skin tests) and in vitro tests are investigated intensively as tools to identify the disease-eliciting drug. One of the tests evaluated in drug allergy is the basophil activation test (BAT). Basophils with their high-affinity IgE receptors are easily accessible and therefore can be used as indicator cells for IgE-mediated reactions. Upon allergen challenge and cross-linking of membrane-bound IgE antibodies (via Fc-epsilon-RI) basophils up-regulate certain activation markers on their surface such as CD63 and CD203c, as well as intracellular markers (eg, phosphorylated p38MAPK). In BAT, these alterations can be detected rapidly on a single-cell basis by multicolor flow cytometry using specific monoclonal antibodies. Combining this technique with in vitro passive sensitization of donor basophils with patients' serum, one can prove the IgE dependence of a drug reaction. This article summarizes the authors' current experience with the BAT in the diagnostic management of immediate-type drug allergy mediated by drug-specific IgE antibodies.