In vitro stimulation of bovine peripheral blood lymphocytes: analysis of variation of lymphocyte blastogenic response in normal dairy cattle.

Lymphocyte immunostimulation tests were performed on 12 lactating dairy cows once every 2 weeks for 1 year. The results indicated that the greatest response of peripheral blood lymphocytes to mitogens occurred in 4- to 6-year-old cows in the month of August and in cows at 2 months before the end of the gestation and again at 1 month after parturition. The least lymphocyte mitogenic response was shown in 7- to 9-year-old cows in the month of February or at parturition and 2 to 4 months after parturition. The magnitude of variations in lymphocyte blastogenic response is reported.