After proliferation and activation of NKT cells in vitro by α-GalCer (KRN7000), the result showed that the IL-4 secreted by NKT cells increased significantly in asthma (P < 0.01) than normal control group, particularly at 72 hours; while the IL-4 in SIT group was significantly decreased compared with asthma group (P < 0.01) and there was no significant difference between normal control group and SIT group (P > 0.05). Here, IL4 is linked to asthma.