Immunohistochemical localization of Pasteurella haemolytica A1-derived endotoxin, leukotoxin, and capsular polysaccharide in experimental bovine Pasteurella pneumonia

Six, 5- to 10-week-old male Holstein calves were inoculated intratracheally with 5 x 10(9) logarithmic growth phase Pasteurella haemolytica biotype A serotype 1 (A1). Immunohistochemical techniques in conjunction with the use of monoclonal antibodies directed against P. haemolytica A1-derived lipopolysaccharide (LPS), capsular polysaccharide, and a polyclonal rabbit anti-leukotoxin antibody were used to localize their respective antigens in tissue sections of pneumonic lung at the light and electron microscopic levels. We found the following: 1) LPS, capsular polysaccharide, and leukotoxin were released into the inflammatory exudate; 2) LPS was found within the cytoplasm of neutrophils (located in the alveolus and alveolar wall), alveolar macrophages, endothelial cells, pulmonary intravascular macrophages, and on epithelial cell surfaces; 3) capsular polysaccharide was found in the alveolus and alveolar macrophages but not in cells of the alveolar wall; and 4) leukotoxin was associated with cell membranes of degenerating inflammatory cells located in the alveolus. This is the first study that demonstrates the presence of leukotoxin in the pulmonary inflammatory lesions caused by P. haemolytica A1 and implicates endotoxin as an important factor in the genesis of the pulmonary lesions.     

Immune profile of infectious bursal disease. III. Effect of infectious bursal disease virus on the lymphocyte responses to phytomitogens and on mixed lymphocyte reaction of chickens

A whole-blood-culture technique was used to sequentially evaluated peripheral blood lymphocyte responses to phytohemagglutinin (PHA) and concanavalin A (Con A) of normal chickens and chickens infected at 1 day or 3 weeks of age with infectious bursal disease virus (IBDV). This method had numerous advantages over the more conventional techniques. A comparative study was made on the percentage of inhibition of responses of peripheral blood lymphocytes to PHA and Con A of 1-day- and 3-week-old IBDV-infected chickens. In both groups, there was a minimum inhibition between 3 and 4 weeks postinfection (PI) and a maximum inhibition at 6 weeks PI. A one-way mixed lymphocyte reaction (MLR) was performed using mitomycin-C-treated cells as stimulator cells obtained from chickens of genetically different strains. Lymphocytes from the experimental birds (control, 1-day-infected, and 3-week-infected groups) were used as the responder cells. The results showed that MLR response of the IBDV-infected chickens was significantly reduced compared with those of the uninfected controls. The degree of lowered response was much more severe in chickens infected at 1 day of age than in those infected at 3 weeks of age.