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. 2002 Dec;161(6):2195–2207. doi: 10.1016/S0002-9440(10)64496-3

Figure 2.

Figure 2.

A: Lung section from BRSV-infected calf IX-2, killed on PID 2. Replication of BRSV is demonstrated by in situ hybridization using a negative sense probe. Black silver grains cover positive cells (arrowheads). Hematoxylin counterstain. B: Parallel section to A. BRSV antigen is demonstrated by immunohistochemistry. The red BRSV antigen-positive cells correspond to cells replicating BRSV in Figure 1A ▶ (arrowheads). Hematoxylin counterstain. C: BRSV-infected calf IX-5, killed on PID 4. BRSV antigen, reflecting replication, is demonstrated in most bronchial epithelial cells. Notice the high amount of antigen in the cilia. Immunohistochemistry, BRSV antigen-positive cells are red. Hematoxylin counterstain. D: Extensive numbers of bronchial, bronchiolar, and alveolar cells containing BRSV antigen (reflecting replication) are seen in BRSV-infected calf XIV-3, killed on PID 6. Immunohistochemistry, BRSV antigen-positive cells are red. Hematoxylin counterstain. E: BRSV-infected calf XIV-2, killed on PID 6. BRSV antigen (reflecting replication) is recognizable in alveolar type I epithelial cell (arrows) whereas the large protruding cell (arrowhead) could be an alveolar type II epithelial cell or an alveolar macrophage. Immunohistochemistry, BRSV antigen-positive cells are red. Hematoxylin counterstain. F: BRSV-infected calf IV-5, killed on PID 8. Double immunohistochemistry using anti-cytokeratin and anti-BRSV antibodies. Epithelial cells are red whereas BRSV antigen-positive cells are clear blue. Double-positive cells (BRSV antigen-positive epithelial cells) become purple. Several double-positive BRSV-replicating epithelial cells are seen one of which is situated in an alveoli and could be mistaken for an alveolar macrophage (arrowhead). Also a single-positive, BRSV antigen-containing (blue) cell is situated in the alveoli (arrow). These cells were very rarely seen, but are probably alveolar macrophages containing BRSV antigen. No counterstain. G: BRSV-infected calf IV-5, killed on PID 8. Double immunohistochemistry using anti-cytokeratin and anti-BRSV antibodies. Two large double-positive alveolar type II epithelial cells replicating BRSV are seen (arrowheads). Hematoxylin counterstain. H: BRSV-infected calf XIV-3, killed on PID 6. BRSV antigen, reflecting replication, is demonstrated in the epithelial cells covering tonsilla pharyngea, whereas there is no replication in the lymphoid tissue below the epithelium. Immunohistochemistry, BRSV antigen-positive cells are red. First part of the calf number refers to the experiment number; last part of the number is the individual calf number. The inoculum in experiment number IV consisted of lung wash fluid from a BRSV-infected calf whereas BRSV-infected fetal bovine lung cells were used for inoculum in experiments IX, XI, and XIV. Original magnifications: ×10 (D); ×50 (A, B, and H); ×100 (C, E, and F); ×250 (G).