Our data demonstrated that IL-9−/− PCP mice demonstrated similar levels of B cell number, production of total serum antibodies and anti-Pneumocystis serum antibodies with WT PCP mice 3-week postinfection (shown in Supplementary Materials), indicating that IL-9 deficiency might play little role in the production of serum antibodies, and the difference of Pneumocystis burdens between WT and IL-9−/− mice 3-week postinfection was largely irrelevant to the antibodies in serum. The gene discussed is IL9; the disease is pneumocystosis.