Statistically significant differences were observed in Treg, Th1, Th2, Th17 and Th1/Th2 values among the recurrent infection group, asthma group and control group (CD3+, CD4+, CD8+, CD4+/CD8+<0.05), and the expression levels of IL-4, IL-17 and IL-21 in the three groups also showed statistically significant differences (P<0.05). The gene discussed is IL21; the disease is infection.