Purified CD4+ T cells were separated from PBMCs of children with allergic asthma, and were stimulated with plate-coated anti-CD3 in the presence or absence of 20 ng/ml IL-9 for 3 days, the concentration of IFN-γ in the supernatants were then detected by ELISA (Fig. 2b). Here, IFNG is linked to allergic asthma.