Phytohaemagglutinin P (PHA) was used as a polyclonal activator to induce in vitro activation of bovine lymphocytes purified from peripheral blood by isopicnic centrifugation on Ficoll Hipaque gradients. After 3 days of incubation, human recombinant IL-2 was added to the cell cultures, to induce a long term proliferation of the cells. Over the cell culture period (12 days) the expression of membrane molecules was investigated by FACS analysis by using the corresponding monoclonal antibodies recognising the membrane antigens. The following markers were monitored at 2 day intervals: BoCD4, BoCD8, MHC II DR and gamma delta subset. The study was conducted from lymphocytes from 5 steers. It was concluded that upon activation BoCD4, BoCD8 and DR molecules seem to be upregulated. In contrast, a decrease in gamma delta subset was detectable during activation period with PHA and IL- 2.
