Plasma IgE levels, activation marker expression, and cytokine production in non-atopic individuals

Background: Since human IgE serum levels are very low compared with the other immunoglobulin isotypes, most studies have examined the regulation of IgE production in severely atopic individuals where serum IgE levels are increased. Since atopy is a pathologic consequence of increased IgE production, this disease state could have other influences that result in abnormal expression of these parameters and may not reflect normal IgE regulatory mechanisms. Objective: To study nonatopic individuals to examine the expression of IgE regulatory cytokines as well as additional cell surface activation markers in relation to serum IgE levels. Method: We selected ten individuals at both the lower and higher end of a spectrum of plasma IgE concentrations from 29 nonatopic individuals and compared the differences in cytokine and activation marker expression in relation to IgE production. Results: We found that even upon extensive examination of activation markers on T, B, and NK cell subsets, there are no significant differences in the cell populations or surface marker expression between the high IgE and low IgE groups. Messenger RNA expression in peripheral blood mononuclear cells (PBMCs) of the cytokines IL-4 and IL-6 was significantly higher, whereas IL- 10 was lower in the high IgE group. In addition, upon in vitro polyclonal stimulation of peripheral blood mononuclear cells, individuals of the high IgE group produced lower levels of IL-2, IFNγ and IL-10 compared to the low IgE donors. Conclusion: Since our results differ from studies using atopic individuals, this study demonstrates the importance of using nonatopic individuals for examining associations between various immune parameters and IgE.