Neutrophils as one of the major haptoglobin sources in mastitis affected milkI-Hsiang Lai1, Jung Hsu Tsao2, Yi Ping Lu3, Jai Wei Lee4, Xin Zhao5, Feng Lin Chien1 and Simon J.T. Mao1, 6
1 Institute of Biochemical Engineering, College of Biological Science and Technology, National Chiao Tung University, 75 Po-Ai Street, Hsinchu, Taiwan, R.O.C.
2 Yong Rong Dairy Farm, Chyayi, Taiwan, R.O.C.
3 Pingtung County Livestock Disease Control Center, Pingtung, Taiwan, R.O.C.
4 Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Pingtung, Taiwan, R.O.C.
5 Department of Animal Science, McGill University, Quebec, Canada
6 Department of Biotechnology, Asia University, Taichung, Taiwan, R.O.C.
Received 17 July 2008; accepted 16 December 2008; published online 19 December 2008
Abstract - The antioxidant haptoglobin (Hp) is an acute-phase protein responsive to infectious and inflammatory diseases. Hp and somatic cell counts (SCC) are sharply elevated in bovine milk following intramammary administration of endotoxin or bacteria. However, the sources of milk Hp responsible for such increases are not fully understood. The purpose of this study was to define the source of milk Hp from dairy cows with naturally occurring mastitis. Quarter milk samples selected from 50 dairy cows were separated into four groups according to SCC as group A: < 100 (n = 19); B: 100–200 (n = 10); C: 201–500 (n = 10); and D: > 500 103 (n = 11) cells/mL. Our results reveal that milk Hp concentrations were correlated with SCC (r = 0.742; P < 0.01), and concentrations in group D were ~10-fold higher than in group A. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicates that the milk somatic cells from group D were not only capable of synthesizing Hp but could also markedly increase Hp mRNA expression. Western blot, immunocytochemistry, double confocal immunofluorescence, and Hp releasing experiments demonstrate that neutrophils were associated with the biosynthesis and release of Hp in milk. It further shows that Hp was significantly elevated in the epithelium of mammary gland tissue with mastitis and was also expressed in the cultured mammary epithelial cells. We propose that neutrophils and epithelial cells may play an essential role in elevating milk Hp in addition to previous suggestions that Hp may be derived from mammary tissues and circulation.
Key words: haptoglobin / neutrophil / mastitis / MAC-T cells / immunocytochemistry
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