Abstract
The sequence of antigen accumulation in the lung of mice infected intraperitoneally with PR8 strain of influenza virus was pursued by means of immunofluorescent (IF) staining. Influenza infection following intraperitoneal inoculation will be characterized by the fact that only when a large inoculum of virus was injected, around 50% of mice succumbed to generalized pneumonitis 6 days after infection. In such infections, virus growth in the lung reached a maximum at 3 days following virus inoculation, and at this stage, pathological features of mouse lung were comparable to those after intranasal instillation. However, initial spread of virus in the lung was found to be different from that after intranasal inoculation. IF was detected as early as 30 min in reticular cells locating along the lymphsinus of parabronchial lymph nodes, and this IF diminished at 24 hr. Since then, the infection spread through alveolar sac and IF was detectable in both type A and B alveolar cells. Ascending mode of infection through bronchioles was then detected from 24 hr and the intensity of IF in the epithelial cells along bronchial lining reached maximum at 120 hr.
