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Baseline CD63 Expression in Patients with Exercise Induced Anaphylaxis (EIA)
Saturday, March 5, 2016
South Exhibit Hall H (Convention Center)
Liat Nachshon, MD, Moshe Appel, PhD, Michael R Goldberg, MD PhD, Arnon Elizur, MD, Yitzhak Katz, MD FAAAAI
Rationale:

Exercise-induced anaphylaxis is a rare, potentially fatal syndrome diagnosed by an exercise challenge. No cellular correlates are definitively associated with this syndrome. The relevance of the Basophil Activation Test (BAT) as an EIA marker was investigated. 

Methods:

Patients with medically documented EIA (n=4, two without atopic background), and controls (n=4), were evaluated by standardized pulse-controlled ergometry followed by maximal effort treadmill running. The exam was stopped with the first objective signs of an allergic reaction or upon physical fatigue. Whole blood before and after exercise, was incubated with RPMI and IL3 or with addition of anti-IgE. Bloods from six atopic patients without EIA, were also tested.  The ratios of the geometric mean fluorescent intensities of APC-anti CD63 or PE-anti CD203c over those of their respective isotype controls (termed CD63-Ratio and CD203-Ratio, respectively), were calculated on HLA-DR-, CD123+ gated basophils. 

Results:

The CD63-Ratio in IL3-treated basophils was significantly higher in EIA patients than in controls, in samples taken before exercise (ranges:5.2-8.7 versus 2.8-3.7, respectively, p=0.03 Student's two-tailed t test) and after exercise (ranges: 3.9-7.9 versus 2.2-2.9, p=0.04). No differences in CD203-Ratio were observed between the EIA and control groups. Interestingly, the CD63-Ratio for the atopic, non-EIA patients (range: 3.8-8.0) was also elevated in relation to the controls (p=0.004). No differences in the CD63-Ratio or the CD203-Ratio between the EIA and control groups were observed in anti-IgE treated basophils, before or after exercise. 

Conclusions:

The elevated baseline CD63 expression in EIA patients may reflect a reactive basophil population, which may emerge independently of atopy.