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Concomitant lipopolysaccharide-induced transfer of blood-derived components including immunoglobulins into milk
M Lehmann1, O Wellnitz, R M Bruckmaier
1Veterinary Physiology, Vetsuisse Faculty University of Bern, Bremgartenstrasse 109a, CH-3001 Bern, Switzerland.
Insights
Lipopolysaccharide (LPS) infusion during mastitis increases blood components in milk, indicating a leaky blood-milk barrier. These changes, while blood-derived, may not benefit the mammary immune system.
Area of Science:
- Veterinary Immunology
- Dairy Science
- Animal Physiology
Background:
- Mammary immune responses compromise blood-milk barrier integrity, leading to increased permeability.
- Lipopolysaccharide (LPS) is a key component of bacterial cell walls, often implicated in mastitis.
Purpose of the Study:
- To determine the blood origin of milk constituents during early-stage LPS-induced mastitis.
- To investigate changes in immunoglobulin and other component concentrations in blood and milk post-LPS challenge.
Main Methods:
- Lactating dairy cows were infused with LPS in one udder quarter and monitored for 8 hours.
- Blood and milk samples were collected hourly to analyze somatic cell count, lactate, BHBA, LDH, and immunoglobulins (IgG1, IgG2).
- An in vitro experiment assessed the impact of milk cell disruption on lactate and LDH levels.
Main Results:
- LPS challenge significantly increased somatic cell count, lactate, BHBA, LDH, IgG1, and IgG2 in challenged quarters.
- Elevated blood lactate concentrations post-LPS indicated a systemic response.
- Increased nonspecific antibodies in milk suggested enhanced transfer from blood due to barrier dysfunction.
Conclusions:
- Intramammary LPS infusion triggers a systemic response and elevates blood components in milk.
- The observed increases in milk constituents are blood-derived, confirming compromised blood-milk barrier integrity.
- Increased blood component transfer into milk is likely a consequence of barrier leakage, not a direct immune benefit.
Abstract:
During a mammary immune response, the integrity of the blood-milk barrier is negatively affected and becomes leaky. The aim of the present study was to demonstrate the blood origin, and to investigate changes in the concentration, of various constituents including immunoglobulins in blood and milk during the early phase of lipopolysaccharide (LPS)-induced mastitis. Five lactating dairy cows received continuous β-hydroxybutyrate (BHBA) clamp infusions to maintain elevated BHBA blood concentrations (1.5 to 2.0 mmol/L) from 48 h before and 8h after LPS administration. One udder quarter was infused with 200 μg of Escherichia coli LPS. A second quarter served as control. Milk and blood samples were taken hourly for 8h postchallenge (PC). The somatic cell count in LPS-challenged quarters was increased from 4h PC to the end of the experiment compared with control quarters. In LPS-challenged quarters, l-lactate, BHBA, lactate dehydrogenase (LDH), IgG(1), and IgG(2) were increased at 3h PC and remained elevated until the end of experiment (8h PC) compared with control quarters. In addition, the optical density values in milk in a nonquantitative ELISA for antibodies directed against bluetongue virus (used as a measure of nonspecific antibody transfer; all animals were vaccinated) increased and, thus, indicates an increase in these antibodies in response to LPS treatment. l-Lactate concentration also increased in blood 2h PC and in the milk of control quarters during the experiment from 3h PC. A second experiment was conducted in vitro to investigate a possible contribution from destructed milk cells to l-lactate concentration and activity of LDH in milk. Aliquots of milk samples (n=8) were frozen (-20°C) or disrupted with ultrasound, respectively. Freeze thawing and ultrasound treatment increased LDH in milk samples, but had no effect on l-lactate concentrations. Results suggest that intramammary infusion of LPS induces a systemic response, as evidenced by an elevation of blood l-lactate concentration. The concomitant changes of all investigated components suggest that they were blood derived. However, the increase in blood components in the milk is not necessarily supportive of the mammary immune system, and likely a side effect of reduced blood-milk barrier integrity.
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