New pathways and hypotheses continue to be described in the etiopathogenesis of early drug hypersensitivity reactions (DHR) to antibiotics such as penicillin and drugs such as aspirin and nonsteroidal anti-inflammatory drug (NSAID). The best-known hypotheses are the hapten/prohapten and pharmacological interactions (p-i) concept (1).Hapten/Pro-hapten concept: Small-molecular-weight drugs (hapten) and the reagent intermediates/metabolites (pro-hapten) formed after the metabolism of the drug cannot cross-link with Fcε-RI by themselves (2). In reference to the concept of hapten and pro-hapten, it is thought that basophils play a role in early developing DHRs.
P-i concept:T lymphocytes develop delayed-type immune reactions in the result of the interaction of the drugs (lidocaine, sulfamethoxazole, lamotrigine, etc.) with T cells via immunoreceptors, and basophils do not have any role here (3).As these three hypotheses reveal, it is understood that basophils and their activation play a role in the development of early DHR. The diagnosis of early DHR is usually dependent upon the history, prick, or intradermal skin tests and the determination of the amount of specific immunoglobulin E (IgE) antibodies that develop against the drug (4). These methods are often insufficient in IgEmediated reactions and useless in non-IgE-mediated reactions. Although drug provocation tests are accepted as the gold standard, they cannot always be performed because of ethical and practical reasons (5). Therefore, there is a need for the development of in vitro tests such as basophil activation test (BAT), which is based on the examination of cells (basophil and mast cell) involved in such allergic reactions (6).Basophil activation test is a test showing IgE-mediated and non-IgE-mediated mast and basophil cell degranulation. Stimulation with stimulant drug or metabolite is based on the identification of basophils by flow cytometry (anti-IgE, CCR3, CRTH2, and CD203c expression, etc.) and on their activation level (through the expressions of CD63 and CD203c) (7).
Basophil Activation in Immediate Drug Hypersensitivity Reactions and Basophil Activation Test (BAT)In the basophil activation test (BAT), the expression of the degranulation marker lysosomal-associated membrane glycoprotein-3, also termed as CD63, or upregulation of CD203c is determined. Degranulation is the fusion of specific intracellular vesicles filled with preformed mediators, which are the so-called granules, with the plasma membrane and the transition of CD63 from inside out. The result is a sudden and pronounced rise, i.e., log shift, of the fluorescence intensity signal in the detection of surface CD63 molecule. Concomitantly, the upregulation of CD203c has been observed; this can be detected as a significant increase in the mean fluorescence intensity signal of the CD203c detection antibody. The most common identification strategies use surface IgE, eotaxin CC chemokine receptor 3, the interleukin-3 receptor alpha chain CD123, the prostaglandin D2 receptor CRTH-2, or the ba...