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Title: REDUCTION OF PULMONARY MAST CELLS IN AREAS OF ACUTE INFLAMMATION IN CALVES WITH MANNHEIMIA (PASTEURELLA) HAEMOLYTICA PNEUMONIA

Author
item RAMIREZ-ROMERO, R - ISU, AMES, IA
item Brogden, Kim
item GALLUP, J - ISU, AMES, IA
item DIXON, R - ISU, AMES, IA
item ACKERMANN, M - ISU, AMES, IA

Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2000
Publication Date: 7/1/2000
Citation: N/A

Interpretive Summary: Respiratory tract diseases are a leading cause of loss from disease in the cattle, sheep and goat industries. Annual loss in the United States is estimated to exceed one billion dollars. Losses are from mortality, reduced feed efficiency, and slaughter condemnations, as well as prevention and treatment measures. Currently, not all the factors leading to the development of pneumonia are known by scientists and veterinarians. As part of our ongoing studies to understand the disease process, we found that mast cells in infected lung tissue are significantly lower that in surrounding normal lung tissue. This observation suggests that mast cells may be degranulated and that granule contents may contribute to the extent and severity of the lung lesion. On the basis of our findings, it appears that this would be an important factor in the disease process that may be used to better control shipping fever of cattle. Corollary benefits include an increase in the profitability and international competitiveness of the U. S. cattle industry, a stronger rural economy, and a continued supply of inexpensive, wholesome beef, and beef products for the American consumer.

Technical Abstract: Mast cells were quantified in the left cranial lobe of lungs of colostrum-d ed neonatal calves that received an intrabronchial deposition of live Pasteurella haemolytica A1. Controls received pyrogen-free saline by similar procedure. These groups were subsequently subdivided for euthanasia at 2 and 6 h post inoculation. An additional group euthanatized at 6 h received a synthetic sialyl Lewisx mimetic (TBC1269) intravenously 30 min before and 2 h after the bacterial challenge. TBC1269 inhibits the adhesion between the selectin family of adhesion molecules and their sialylated lactosamines receptors. Mast cells were characterized by immunohistochemistry employing mouse anti-human mast cell tryptase monoclonal antibody and also by metachromatic staining employing Low pH Toluidine Blue. Although immunohistochemistry yielded an excellent demonstration of tryptase positive mast cells, the Low pH Toluidine Blue stain demonstrated a significantly higher number of mast cells (p<0.01). The lungs of animals receiving P. haemolytica and euthanatized at 6 h, including the TBC1269 treated group, had decreased numbers of mast cells in comparison with those that received saline (p<0.05); this difference was not perceived at 2 h post inoculation (p>0.05). Nonetheless, the significant differences were restricted to those sites in the lung showing typical fibrinopurulent or fibrinohemorrhagic lesions.