Submitted to: European Society of Veterinary Pathology
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 1995
Publication Date: N/A
Technical Abstract: Introduction: Neutrophils that lack CD18 expression have impaired infiltration into sites of infection. Neutrophils from cattle with BLAD have <1% expression of CD18 and do not enter sites of infection in most tissues. Materials: Spontaneous cases (1 chronic and 2 acute) of pneumonia from 3 cattle with BLAD were recognized clinically and at necropsy. Acute pneumonia was induced experimentally in 3 cattle with BLA and 4 cattle with normal CD18 expression by bronchoscopic instillation of Pasteurella haemolytica A1 into the right cranial lung lobe of cattle; left cranial lung lobes received pyrogen-free saline (PFS). Lung from all cattle were processed for histopathology, and experimental lung tissue was stained for cytokeratin and macrophages (CD68). Neutrophil infiltration was semi-quantitated in experimental pneumonias by computerized image analysis. Results: Similar to previous reports, cattle with spontaneous pneumonias had dense infiltrates of neutrophils. By image analysis, experimental pneumonias had similar infiltrates of neutrophils into the lumens of alveoli at 4 and 6 hours PI when compared to control cattle. Cattle with BLAD, however, had increased numbers of neutrophils in alveolar septal walls of both non-infected and P. haemolytica-inoculated lobes. Discussion: This work demonstrates that CD18- neutrophils can enter the alveolar lumen during spontaneous and experimental pneumonia. Increased numbers of CD18- neutrophils are present in the septa of lung alveoli. Accumulation of CD18- neutrophils in the septa may be due to impaired passage across the alveolar wall. Studies at timepoints <4 hours PI are needed to determine if passage is impaired at earlier stages.