Evaluation of Th1/Th2 ratio and cytokine production profile during acute exacerbation and convalescence in asthmatic children

Th2-type cytokines, such as IL-4 and IL-5, are generally believed to play an important role in the pathogenesis of allergic asthma. In contrast, Th1-type cytokine, especially interferon (IFN)-γ, is thought to have a downregulatory effect on Th2 immune response cells. Thus, the imbalance of Th1 and Th2 cells may be a key factor in relation to disease severity. The aim of this study is to examine the changes in the Th1/Th2 ratios and cytokine production profiles of asthmatic children at acute attacks and convalescent stages. Twelve asthmatic patients were included in this study. The percentages of IFN-γ- or IL-4-producing cells were determined with a flow-cytometric method of intracellular protein detection. Fresh whole blood obtained from normal controls and patients at two stages was stimulated with brefeldin A, phorbol myristate acetate, and ionomycin for 4 hours. Cells were fixed and stained intracellularly with fluorescein isothiocyanate- or phycoerythrin-conjugated antibody specific to each cytokine in combination with anti-CD4. ELISA assays were applied to measure cytokine concentrations of supernatant from peripheral blood mononuclear cells (PBMC) activated with phorbol myristate acetate and ionomycin for 24 hours. Among CD4 + cells, the percentage of IL-4 + cells decreased significantly from 8.18 ± 4.77% at acute attacks to 4.18 ± 1.26% ( P < .020) at convalescence. The percentage of IFN-γ + cells also decreased from 13.49 ± 4.21% to 9.03 ± 5.42% ( P < .052). The Th1/Th2 ratios of patients at the two stages were similar, and both were lower than the normal controls. Significantly higher IL-5 and lower IFN-γ production were detected from activated PBMC of asthmatic patients than normal controls. The decrease of IFN-γ + and IL-4 + cells detected at the single-cell level may explain the potential mechanism of convalescence from acute asthma attacks. High Th1/Th2 ratio and low IL-5 production from the PBMC of normal controls support the idea of a biased Th2 immune response in asthmatic patients.