L-selectin and beta2-integrin expression on circulating bovine polymorphonuclear leukocytes during endotoxin mastitis

Area of Science:

• Veterinary Immunology
• Bovine Mastitis Research
• Inflammatory Response Mechanisms

Background:

• Bovine mastitis, particularly coliform mastitis, involves complex inflammatory pathways.
• Adhesion molecules on neutrophils play a critical role in their migration and function during infection.
• Understanding endotoxin's impact on these molecules is key to managing mastitis.

Purpose of the Study:

• To investigate the in vivo effect of intramammary endotoxin (lipopolysaccharide, LPS) on bovine neutrophils.
• To analyze the expression of L-selectin (CD62L) and beta2-integrin subunits (CD11b, CD18) on circulating neutrophils.
• To correlate changes in adhesion molecule expression with clinical parameters of inflammation.

Main Methods:

• Intramammary infusion of Escherichia coli LPS into early lactating cows.
• Flow cytometric analysis of cell surface adhesion molecule expression on peripheral blood neutrophils.
• Measurement of clinical parameters: rectal temperature, blood cortisol, somatic cell count (SCC), and leukocyte counts.

Main Results:

• LPS infusion decreased CD62L expression and increased CD11b and CD18 density on neutrophils.
• Changes in adhesion molecule expression correlated with decreased circulating neutrophils, fever, elevated cortisol, and increased SCC.
• No direct correlation found between CD11b and CD18 expression kinetics.

Conclusions:

• Intramammary LPS administration significantly modulates adhesion receptor expression on bovine neutrophils.
• Endotoxin plays a key role in the inflammatory cascade during bovine mastitis.
• CD18 variation during endotoxemia is not solely driven by CD11b upregulation, differing from clinical mastitis observations.