The increased incidence of lung infection in patients with immunoglobulin deficiencies (16, 80), HIV infection (81), or inherited disorders affecting IL-17 pathways [e.g., hyperIgE syndrome (82)], do indicate roles for both antibody and Th17 CD4+ cells for protection against S. pneumoniae pneumonia in humans as well as mice. The gene discussed is CD4; the disease is susceptibility to pneumonia measurement.