Altered Expressions of Helper T Cell (Th)1, Th2, and Th17 Cytokines in CD8+ and γδ T Cells in Patients with Allergic Asthma

Background. T cells play an important role in orchestrating allergic asthma by producing various cytokines; however, little information is available on the phenotype of cytokine-producing T cells, especially CD8(+) T and gamma delta T cells in humans. Objective. The aim of this study was to investigate the role of cytokine expressions from circulating CD4(+), CD8(+), and gamma delta T cells in patients with allergic asthma. Methods. Peripheral blood mononuclear cells were isolated from patients with allergic asthma (n = 29) and healthy controls (n = 12). The percentage of helper T cell (Th)1-, Th2-, and Th17-type cytokines interferon-gamma (IFN-gamma), interleukin (IL)-4, and IL-17, respectively, of CD4(+), CD8(+), and gamma delta T cells was analyzed by flow cytometry. Results. The percentages of IL-4(+) and IL-17(+) CD4(+) T cells increased, whereas IFN-gamma(+) CD4(+) T cells decreased in patients with allergic asthma compared with healthy controls. The frequency of IL-17(+) CD4(+) T cells tended to increase with the severity of allergic asthma. Higher frequency of IL-4-producing and lower frequency of IFN-gamma-producing CD8(+) and gamma delta T cells were found in patients with allergic asthma compared with healthy controls. The IFN-gamma(+)/IL-17(+) ratio among CD4(+), CD8(+), and gamma delta T cells was significantly decreased in patients with allergic asthma compared with healthy controls. Conclusion. CD8(+) and gamma delta T cells might be involved in the pathogenesis of allergic asthma through the release of Th1-, Th2-, and Th17-type cytokines.