(A) Case #3. Infiltration of the airway wall by lymphocytes and plasma cells (arrows), PAS stain, scale bar, 80 μm. (B) Case #1. Obstruction (arrows) of bronchi and small bronchioles was a striking feature in otherwise unaffected lung (asterisks). HE stain, scale bars, 0.75 mm. (C) Airways from non-CF and CF pigs were scored for the most severe degree of leukocytic infiltration detected with the following scale: 0 – no leukocytes detected; 1 – rare individual to scattered leukocytes occasionally seen in airway wall with lack of cellular aggregates; 2 – grade 1 plus minor to moderate leukocyte aggregates detected in wall ± rare in lumen; 3 – grade 2 plus in multiple airways, with early wall injury, and luminal leukocytic aggregates; and 4 – grade 3, plus airway wall destruction, leukocytes filling and obstructing airways. For grades 1 and 2, leukocytes were primarily lymphocytes and plasma cells, and for grades 3 and 4, leukocytes were primarily neutrophils. Each point represents a sample from a different animal. CF pigs airways had more severe scores of airway infiltration (*P <0.05, Mann-Whitney, horizontal line indicates the median). (D) Case #4. Airways (left panels, scale bar, 0.7 mm) ranged from relatively unaffected (top) to severe disease (bottom, note that luminal mucocellular plug was removed at necropsy) with airway wall thickening. Surface epithelium (right panels, scale bar, 70 μm) ranged from near normal (top) to mucinous and hyperplastic change (asterisks) in moderate to severe disease (middle and bottom panels). Note that hypertrophy/hyperplasia of submucosal glands (arrows, bottom right) was uncommon and generally restricted to the most severe and chronically affected airways.