In order to clarify the mechanism of MP infection-related type 1 hypersensitivity disease for children with pneumonia, we launched a prospective study to determine the spectrum of serum cytokines and a series of other immune indices, including levels of IgE, IL-4, IL-6, IL10, and INF-γ and T-cell status in children with pneumonia at acute and convalescence phases of MP infection. This evidence concerns the gene IL4 and susceptibility to pneumonia measurement.