Submitted to: Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/14/2007
Publication Date: 11/1/2007
Citation: Sohn, E.J., Paape, M.J., Connor, E.E., Bannerman, D.D., Fetterer, R.H., Peters, R.R. 2007. Bacterial lipopolysaccharide stimulates bovine neutrophil production of TNF-alpha, IL-1beta, IL-12 and IFN-gamma. Veterinary Research. 38(6):809-818. Interpretive Summary: White blood cells play an important role in the host defense against infections by Escherichia coli. Of all the clinical cases of bovine mastitis that occur annually, 40% are caused by E. coli. When E. coli invades the mammary gland, the milk in the gland provides an ideal source of nutrients for bacterial growth. Soon the few invading bacteria explode into the millions, settle next to the delicate lining of the mammary gland and secrete tissue destroying toxins. These toxins also activate mammary cells causing them to start secreting proteins called cytokines that initiate the migration of a white blood cell called the neutrophil from blood into the milk. Neutrophils possess phagocytic and bactericidal killing mechanisms and soon start to devour the swarming hoard of bacteria. Scientists at Beltsville discovered that neutrophils can also secrete cytokines that are important in directing the inflammatory response to a more rapid cure. Thus, neutrophils should not be considered as just short lived white blood cells but as a major player in directing a supportive role in the immune response to Gram-negative infections.
Technical Abstract: Rapid recruitment and bacterial phagocytosis and killing by neutrophils (PMN) are the most effective defenses against establishment of bacterial infection. In addition to their phagocytic and bactericidal properties, PMN may play a key supportive role through secretion of cytokines during the innate immune response. We sought to determine whether bovine PMN produce cytokines in response to stimulation by lipopolysaccharide (LPS). To investigate the effects of LPS on the expression of cytokines secreted by bovine PMN, we measured the expression of TNF-', IL-1', IL-12, and IFN-' by ELISA after stimulation with different concentrations of LPS, and secretion of IL-8 after co-stimulation with LPS and either TNF-' or IL-1'. Bovine PMN were shown to secrete TNF-', IL-1', IL-12, IL-8 and INF-' in response to LPS. Co-incubation of PMN with LPS and TNF-' increased secretion of IL-8 when compared to LPS alone. It was concluded that LPS stimulation up-regulates the secretion of cytokines by bovine PMN, and that co-incubation of LPS with TNF-' had an additive effect on the secretion of IL-8. These data show that bovine PMN, in addition to their phagocytic and bactericidal properties, may play a supportive role in the innate immune response to infection by Gram-negative bacteria, through their ability to produce immuno-regulating cytokines.