a. New onset of purulent sputum or change in character of sputumb. Organism isolated from blood culturec. Isolation of pathogen from specimen obtained by transtracheal aspirate, bronchial brushing, or biopsyd. Isolation of virus or detection of viral antigen in respiratory secretionse. Diagnostic single antibody titer (IgM) or fourfold increase in paired serum samples (IgG) for pathogenf. Histopathologic evidence of pneumonia. The gene discussed is CD40LG; the disease is susceptibility to pneumonia measurement.