The CXCR1 gene, neutrophils and udder health

1The aim of this thesis is to increase our understanding of the role of polymorphisms in the bovine CXCR1 (IL8RA) gene in mammary gland immunity and udder health. Associations between CXCR1 polymorphisms and neutrophil viability, subclinical mastitis, clinical mastitis and milk yield were detected indicating CXCR1 to be a major gene for mastitis resistance.
Neutrophils play a major role in the mammary gland immunity. Binding of interleukin-8 (IL-8) on chemokine (C-X-C motif) receptor 1 (CXCR1) causes migration from blood to the site of infection and enhances activity and viability of neutrophils. Despite its important function, we have detected 16 polymorphisms in the coding region of CXCR1 potentially affecting IL-8 binding or signal transduction.
In a first study, associations between CXCR1 polymorphisms and viability and concentration of milk neutrophils of 73 early lactating dairy heifers were studied. Resident milk neutrophils showed a lower percentage apoptosis in c.980AG heifers compared to c.980GG heifers. Additional to viability, activity of neutrophils might associate with CXCR1 polymorphisms. To test this hypothesis, reactive oxygen species (ROS) generation of blood neutrophils isolated from twenty early lactating heifers with different CXCR1 genotype was studied. Genotype was neither associated with ROS generation in general nor with the effect of IL-8 incubation on reactive oxygen species generation.

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