FOXP3 and susceptibility to pneumonia measurement: Vitamin A supplement after neonatal S. pneumoniae pneumonia remarkably increased Foxp3+Treg, Th1 cells production when compared to the S.pp/OVA group mice (5.64 ± 2.11% vs 2.75 ± 0.72%, P < 0.001, 2.27 ± 0.36% vs 1.13 ± 0.33%, P < 0.01), while the number of Th17 and Th2 cells significantly decreased (1.93 ± 0.12% vs 2.40 ± 0.25%, P < 0.001, 0.78 ± 0.31% vs 1.50 ± 0.17%, P < 0.01).