Our results show that both CD4+ and CD8+ T-cells are required for maximal clearance of K. pneumoniae. This is consistent with previous reports showing that secretion of IFN-γ from Th1 cells is required for maximal clearance of Klebsiella [14], that both CD4+ and CD8+ T-cell are required for maximal host defense and survival following Klebsiella septicemia [47], and that disruption of the IL-23 axis increases susceptibility to Klebsiella infection [10]. The gene discussed is CD4; the disease is Klebsiella Infections.