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Published on: September 4, 2012
Cytokine production during endotoxin-induced mastitis in lactating dairy cows
D E Shuster1, M E Kehrli, M G Stevens
1Agricultural Research Service, National Animal Disease Center, Ames, IA 50010-0070.
Insights
Interleukin-1 (IL-1) and Interleukin-6 (IL-6) play a role in cow mastitis defense. These cytokines were detected in milk after endotoxin infusion, influencing inflammation and systemic responses.
Area of Science:
- Veterinary Immunology
- Bovine Pathology
Background:
- Bovine mastitis is a significant economic concern in dairy farming.
- Endotoxin-induced mastitis serves as a model to study inflammatory responses in the mammary gland.
Purpose of the Study:
- To characterize the role of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) in endotoxin-induced mastitis in cows.
- To investigate the temporal relationship between clinical signs of inflammation and cytokine expression in milk.
Main Methods:
- Six cows received Escherichia coli lipopolysaccharide infusion into one mammary gland.
- Three cows served as non-treated controls.
- Milk and serum samples were analyzed for cytokine concentrations, somatic cell counts, albumin, cortisol, and temperature.
Main Results:
- Endotoxin infusion caused mammary gland edema and increased milk albumin within 1.5-2.5 hours.
- Milk somatic cell counts and IL-1/IL-6 concentrations increased significantly after infusion.
- Tumor necrosis factor alpha was not detected in milk or serum.
- Clinical signs of inflammation preceded detectable IL-1 and IL-6 levels.
Conclusions:
- IL-1 and IL-6 are likely involved in mammary gland defense mechanisms during endotoxin-induced mastitis.
- These cytokines may contribute to the pathophysiological changes observed in mastitis.
- TNF-α does not appear to play a significant role in this model of bovine mastitis.
Abstract:
The role of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha during endotoxin-induced mastitis in cows was characterized. Six cows had 10 micrograms of Escherichia coli lipopolysaccharide infused into 1 mammary gland. Three other cows served as nontreated controls. Within 1.5 to 2.5 hours after infusion, endotoxin caused obvious edema of the mammary gland and increased serum albumin concentration in milk of infused glands 6 times. Milk somatic cell count began to increase 3 to 5 hours after infusion in all treated glands. At 7 hours after infusion, somatic cell counts were increased > 10 times, compared with counts in milk from control cows. Pyrexia of > 1 C developed in only 1 cow, but all treated cows had serum cortisol concentrations > 50 ng/ml in response to endotoxin treatment. High concentrations of IL-1 (10 to 600 U/ml) and IL-6 (2 to 22 U/ml) were detected in milk of infused glands beginning 2.5 to 4 hours after infusion. Endotoxin did not induce detectable amounts of tumor necrosis factor activity in milk or serum. Swelling and mammary gland permeability changes preceded any detectable increase in IL-1 and IL-6 activity, indicating that these clinical signs of inflammation were not mediated by these cytokines. Systemic responses and the leukocytic influx into endotoxin-infused glands developed after or concurrently with initial increases in IL-1 and IL-6 activities in milk. These results suggested that IL-1 and IL-6 may have a role in mammary gland defenses and in the pathophysiologic changes during endotoxin-induced mastitis.
