Regulatory natural killer cell expression in atopic childhood asthma

Introduction: Different subsets of natural killer (NK) cells were found to play a role in pathogenesis of allergy. We sought to investigate the expression of regulatory NK cells (CD56+CD16+CD158+) in atopic children with bronchial asthma in order to outline the value of these cells as biomarkers of disease severity and/or control. Methods: A cross sectional controlled study was carried out in the Pediatric Allergy and Immunology Unit, Ain Shams University. The study included 45 atopic children [mean age(SD)= (2.9) years] with bronchial asthma (BA) and/or allergic rhinitis (AR)as well as 40 healthy matched controls. Enrolled subjects underwent complete blood counting and flow cytometric measurement of NK cell (CD16+ CD56+) and regulatory NK cells (CD16+CD56+CD158+). Results: Patients had significantly higher regulatory NK cell percentages [mean (SD)= 41 (52) %] than controls [mean (SD)=15 (7.1)]; p ≤0.001. Regulatory NK cell counts and percentages did not vary with the concomitant presence of AR or the degree of asthma control. Regulatory NK cell counts tended to be higher in children with moderate/severe BA compared to those with mild asthma but the difference did not reach statistical significance (U= -1.8, p=0.06). NK cell counts [mean (SD)= 159 (164) cells/μl] and percentages [mean (SD)= 3.7 (3.2) %] were comparable among patients and controls and did not vary with the presence of AR ( p = 0.51, 0.95) or with the degree of asthma control. NK cells absolute counts and percentages tended to be higher among patients with moderate/severe compared to mild asthma but the difference did not reach statistical significance. Conclusions: Regulatory NK cells seem to be increased in childhood asthma. We recommend wider scale prospective studies on steroid-naive subjects involving measurement of cytokines that are secreted by different types of NK cells. Keywords: Natural killer, regulatory, asthma, children, allergy