It has been reported that Th1 cells not only produce Th1 cytokines, but also Th2 cytokines (IFN-γ, IL-3, IL-9, IL-13, and granulocyte-macrophage colony-stimulating factor, GM-CSF) [38, 39], and novel CD4+ subsets that include Th17 cells, Th9 cells, and regulator T cells (Tregs) have emerged as being involved in the pathogenesis of asthma (Figure 2). This evidence concerns the gene IFNG and asthma.