Relationship between maternal and child behaviors in pediatric food allergy-an exploratory study

activation test. Statistical analyses were performed with GraphPad Prism 6.0 (GraphPad, San Diego, California). Doseeresponse curves were fitted to a 4-parameter nonlinear regression model. Data are presented as mean SEM of 14 subjects. Two-tailed t test for paired sampleswasusedtotest fordifferencesbetweenCD63þ cells andCD63 mean fluorescence intensity, respectively, at 4 PM and 4 AM. The significance level was set at P < .05. In this pilot study, we found that basophil sensitivity of volunteers without allergy showed diurnal changes in response to IgEdependent activation. Figure 1 shows a significant decrease in basophil sensitivity at 4 AM (n1⁄4 14, P1⁄4 .0298) when assessed by the mean fluorescence intensity of CD63þ basophils, suggesting that basophils of persons without allergy are less sensitive early in the morning. Notably, we did not find diurnal variation of reactivity assessed by the more commonly used percentage of CD63þ cells in response to anti-IgE at 4 AM and 4 PM (P 1⁄4 .607, data not shown). Hence, our data support the finding that the mean fluorescence intensity is an important parameter in basophil activation test. Mast cells and eosinophils, main effector cells of allergic reactions aside from basophils, recently have been found to exhibit a functional clock mechanism. Clock genes are responsible for generating the circadian rhythm and the clock has been found to control activation of mast cells and eosinophils, resulting in circadian production and release of their mediators.6 These findings assume that the circadian clock influences and controls allergic reactions and not vice versa. Moreover, blood basophil numbers display circadian variations.8 In addition, we found that the intensity of the activation marker CD63 expressed on basophils exhibits diurnal variation. Very recently, daily variations in basophil reactivity have been reported in patients with seasonal allergic rhinitis, with an increase in CD203cþ basophils at 7 AM compared with 7 PM.9 However, we analyzed the circadian rhythm of the sensitivity of basophils of volunteers without allergy. Because donor selection, time points, activation markers, and readout differed between the previous and present studies, the results are not directly comparable. Certainly, further experiments and measurements of more than 2 time points will be necessary to clarify this issue and to explain the higher frequency of allergic symptoms between midnight and morning. At activation, expression of CD63 correlates with degranulation and the release of histamine and with the severity of allergic reactions.2,10 Thus, basophil activation, mediator release, and clock gene expression around the clock and the correlation of circadian allergic symptoms of patients should be analyzed in a follow-up study. In conclusion, this pilot study provides a first hint that the circadian clock might regulate the intensity of basophil response in IgE-dependent allergic reactions.