To establish the effective ways to prevent bovine mastitis, the study has been performed to investigate the attributable factors causing down-regulation of immune responses in mammary gland of non-lactating cows. Lymphocytes from peripheral blood and mammary gland secretions(MGS) were obtained from normal healthy cows and mastitic cows, respectively. Cellular immune responses were examined by comparison of proportion of lymphocyte subpopulations using a set of monoclonal antibodies and flow cytometry.
The results obtained are as follows.
1. Proportions of peripheral blood lymphocyte subpopulations expressing BoCD2 and BoCD4 molecules were 32.9%, 15.4% in mastitic cows and 43.3%, 28.3% in normal healthy cows, respectively. The ratios of BoCD4 to BoCD8 were 0.76 and 1.47, respectively.
2. Proportions of mammary gland lymphocyte subpopulations expressing BoCD2 and BoCD4 molecules were 18.5%, 8.3% in mastitic cows and 38.2%, 14.2% in normal healthy cows, respectively. The ratios of BoCD4 to BoCD8 were 0.6 and 2.0, respectively.
3. Proportions of T lymphocyte subpopulations from MGS were significantly lower than those from peripheral blood both in mastitic cows and normal healthy cows. However, lymphocyte subpopulations expressing ACT2 and ACT3, which represent activated T suppressor cells, were significantly higher in MGS than those in peripheral blood.
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