Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/1998
Publication Date: N/A
Interpretive Summary: The udders of dairy cows are constantly exposed and challenged by millions or coliform organisms. These organisms are especially prevalent in the bedding where cows sleep and account for 50% of all the clinical cases in a herd. The disease is especially debilitating if contracted soon after calving, usually resulting in death of the cow. Death is due to the failure of the udder to control the inflammation caused by the endotoxin being produced by the rapidly multiplying coliform organism in the milk. Researchers at the USDA discovered that udders of cows when first exposed to these endotoxins produce tumor necrosis factor (TNF), an important protein responsible for initiating the inflammatory response. However, a second exposure to exdotoxin did not cause release of TNF. This important finding indicates that the udder has the capability of protecting the cow from an overwhelming inflammatory response, and possibly death, by blocking grelease of TNF after a first time exposure to endotoxin. Discovering the mediators of this down-regulation could have important implications in the treatment and prevention of coliform mastitis.
Technical Abstract: Murine monoclonal antobodies reactive with recombinant bovine tumor necrosis factor-a (r-boTNF-a) were produced. An ELISA using murine monoclonal antibodies and rabbit polyclonal antibodies, each reactive with r-boTNF-a to sandwich bovine TNF-a was developed. Secretion of tumor necrosis factor-a in quarter milk increased 1 h after injection of 0.1 mg (4 cows) or 0.5 mg quarter, peaked 1 to 5 h later, and returned to control levels in 24 h. A second injection of 0.1 mg LPS, 24 h after the first injection, produced a strongly attenuated response when injected into the same quarter but a normal response when injected into a contralateral quarter. Leukocyte counts in blood decreased and body temperature increased substantially at the same time as tumor necrosis factor-a peaked in quarter milk. Quarter milk SCC increased 200-fold 8 to 12 h after the LPS injection. There were no differences in body temperatures. SCC, TNF-a, and blood leukocyte responses between 0.1 and 0.5 mg LPS.