Use of bovine lymphocytes to assess the immunomodulatory effect of natural extracts

A simple and rapid method based on the in vitro bovine lymphocyte proliferation was developed to assess the immunomodulatory activity of natural compounds extracted from plant and foods. The proliferation of lymphocytes was measured by the MTT [3-(4, 5- dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide] assay. This test was used to measure the immuno-enhancing activity of 2 plant extracts and 2 samples of fermented milk after 48 h of incubation. To evaluate the effect of the cow physiological phase on the assay response, the tests were repeat- ed using lymphocytes taken from non-pregnant dry, pregnant dry and post partum cows. The assay was not affect- ed by the cow physiological phase and the results obtained were comparable. Both plant extracts enhanced lym- phocyte growth, in particular the extract 2 was slightly more potent than extract 1. The fermentation of milk with proteolytic starter cultures, such as FAIR E-63 and LA 2, can generate peptidic compounds from milk protein with potential immunostimulating activity. These samples tested in cell culture inhibited lymphocyte proliferation because they showed an acidic pH of 4.5. However, this bioassay was enough sensitive to detect biological activity of different compounds also at low concentrations.