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In conclusion, IL-33, and in a lesser extent IL-6, prime individual MCs for subsequent IgE-mediated activation. Moreover, this priming effect is synergistic. In contrast, none of the cytokines had a priming effect on MRGPRX2-mediated activation of MCs. © 2017 International Clinical Cytometry Society.

Quantification of specific IgE (sIgE) antibodies constitutes an important measure to document anesthesia-related immediate hypersensitivity reactions (IHRs). However, only a few drug-specific assays are available and their predictive value is not known. In cases of non-IgE mediated IHRs, diagnosis might benefit from cellular tests such as basophil mediator release tests and basophil activation tests (BATs). To review the potential and limitations of quantification of sIgE, mediator release, and BAT in anesthesia-related IHRs, a literature search was conducted using the key words allergy, basophil activation, CD63, CD203c, diagnosis, drugs, hypersensitivity, flow cytometry, MRGPRX2, specific IgE antibodies, leukotrienes, histamine, and tryptase; this was complemented by the authors' experience. The drugs and compounds that have predominantly been studied are neuromuscular blocking agents (NMBAs), β-lactams, latex, and chlorhexidine. For sIgE NMBA, sensitivity and specificity varies between 38.5% to 92% and 92% to 100%, respectively. For sIgE β-lactams, sensitivity varies between 0% to 85% and specificity between 52% to 100%. sIgE to morphine should not be used in isolation to diagnose IHRs to NMBAs or opiates. sIgE for latex, and, in difficult cases, molecular diagnosis with quantification of sIgE to Hevea components constitute reliable diagnostics. For drugs, the sensitivity of BAT varies between 50% and 60% and specificity reaches 80% to 90%. Basophil mediator release tests seem to be abandoned and supplanted by BATs.

Peripheral blood cultured mast cells (PBCMCs) are defined as CD117 +ve CD203c +ve cells. PBCMCs harbour two subpopulations: cells with surface expression ofMRGPRX2 (MRGPRX2 +ve) and cells without expression ofMRGPRX2 (MRGPRX2-ve).

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RATIONALE: The MRGPRX2-receptor was shown to be involved in IgE/FcεRI independent activation of both murine mast cells and a human mast cell line (LAD2). We sought to investigate the expression of the MRGPRX2 receptor on human basophils. METHODS: Peripheral blood basophils of 16 atopic patients with birch pollen allergy and 4 controls were studied for intracellular and surface MRGPRX2-expression before and after stimulation with fMLP, anti-IgE and recombinant birch pollen (rBet v 1) using basophil activation technique. Briefly, basophils were gated as low SSc IgE + CD203c + positive cells. MRGPRX2 was measured intracellularly and on the membrane of resting (CD203c + CD63 -) and degranulating (CD203cc ++ CD63 + ) basophils. Data are expressed as median (range). RESULTS: All human basophils constitutively express intracellular MRGPRX2. In contrast, only a minority of resting basophils express MRGPRX2 on their surface membrane. Actually, MRGPRX2 surface expression in patients was found in 4% (0-14%) of the resting cells, and was comparable to expression in controls (6%[4-20%]). In patients, anti-IgE stimulation resulted in a significantly higher percentages of CD203c ++ CD63 + MRGPRX2 + cells (21%[1-58%]) than CD203c + CD63 -MRGPRX2 + (4%[0-14%])(P50.001). Similar observations were done in patients for allergen-specific stimulation and for fMLP (patients 13% [4-28%]; controls 11%[3-33%]). Moreover, in patients anti-IgE stimulation resulted in a significantly higher percentage of CD203c ++ CD63 + MRGPRX2 + cells than fMLP stimulation (21% [1-58%] vs 13% [4-28%]; P50.04). CONCLUSIONS: MRGPRX2 is expressed on human peripheral blood basophils and up-regulated upon cross-linking of IgE/FcεRI and stimulation with fMLP. These results show that basophils could potentially be activated in an IgE-independent pathway through engagement of MRGPRX2. RATIONALE: Basophils are mature circulating granulocytic cells that play an important role in IgE-dependent immune responses. The objective of this study was to prospectively examine, in very early life, basophils for FcεRIa and activation markers, which are involved in a Th2 response. METHODS: Cord blood and venous blood at 6 months of age were obtained from 65 infants enrolled in the MAAP (Microbes, Allergy, Asthma and Pets) birth cohort. Basophil percentages were determined by manual differential count of 200 cells in whole blood smears. The enriched granulocyte fraction collected after Ficoll separation of peripheral blood mononuclear cells was examined by flow cytometry. Basophils were defined as low side scatter/Class II 2/CD123+ cells. Cells expressing FcεRIa or the activation markers CD203c or CD63 were examined and were reported as % of basophils expressing these markers. Paired t-tests were used to assess change over time. RESULTS: Basophils represented a mean 0.78% (range 0 to 2.5%) and 0.88% (range 0 to 4.0%) of the differential among cord and 6 month blood samples, respectively. There was a statistically significant increase from birth to 6 months of age in the proportio...