Distribution of influenza antigens in swine and avian influenza virus infected pigs. The figure sums up the results from demonstration of influenza A virus (infAv) antigens with immunohistochemistry in alveoli, bronchioles, bronchi as well as nasal and tracheal epithelium. The pigs were inoculated with avian influenza A virus (AIV) H4N6 (n = 4 pigs) or swine influenza A virus (SIV) (n = 4) including two H1N1 and two H1N2 infected pigs. The figure shows the number of infAv positive pigs out of the four pigs in each group (AIV and SIV, respectively). For the alveoli, bronchioles, and bronchi the number of infAv positive pigs is averaged over the 9 lung sections (lu1-9).