Date of Award

5-2007

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Gina M. Pighetti

Committee Members

Tim Sparer, Jun Lin

Abstract

Prior research in our lab has demonstrated a significant association between the incidence of subclinical mastitis and neutrophil functions with polymorphisms of the CXCR1 gene in Holstein dairy cattle. The objective of this study was to evaluate the specificity of the response relative to CXCR1 and potential involvement of intracellular signaling pathways. Migration was evaluated in cows of both homozygous genotypes (n=7 each) in response to high and low doses of interleukin-8 (IL -8; specific for CXCR1 and CXCR2), epithelial neutrophil activating peptide (ENA-78; specific for CXCR2) or zymosan activated sera (ZAS; complement receptors). Cows with a GG genotype had significantly more migration in response to both 12.5 and 50 nM doses of IL -8 (p<0.05) compared to cows with a CC genotype. Although a similar trend was observed for 50 nMENA-78 (p<0.07), this was not evident with the 12.5 nM dose. This result was comparable to ZAS, where the 5%dose caused significantly more neutrophil migration in cows with a GG genotype than those with a CC genotype (p<0.03), while the response to the 1% dose of ZAS was similar between genotypes. p38 MAPK and PKB phosphorylation were evaluated prior to and following stimulation with the high doses of each ligand. Relative increases in p38 MAPK phosphorylation were greater in neutrophils from cows with a GG genotype when compared to those with a CC genotype regardless of treatment with rhu-IL-8, rhu-ENA-78, and ZAS or not (p<0.001), But CC cows had higher baseline levels of p38-MAPK phosphorylation than GG cows. Therefore, the lower increase in phosphorylation in neutrophils from CC cows may have been due to higher starting levels. Increases in PKB phosphorylation also were greater in neutrophils from cows with a GG genotype when compared to a CC genotype when treated with ZAS, but not other ligands. Because no differences between genotypes were observed at time zero this may be tied to the altered p38 MAPK pathway. Future research will be aimed at further elucidating the signaling pathways causing functional differences in neutrophils from cows with different CXCR1 genotypes.

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