The effect of Garcinia kola heckel seed extract on the promonocytic cell line U937 activated by lipopolysaccharide (LPS) was investigated. 200 l of U937 cells maintained in culture at 5 x 105 cells perml was delivered into wells of a culture plate according to groups. Cells were pre-treated with 20 l of 100 ng/ml phorbol myristate acetate (PMA) for 24, 48, or 72 h in order to transform them to themacrophage form. Following the PMA treatment, some cells were incubated with 100 g/ml LPS (group C), while others (group D) were treated with 100 g/ml LPS and 100 ìl of 100 g/ml of the G. kolamethanolic extract. Other cells (groups A, and B) were incubated with neither LPS nor extract. 24 h later, the supernatants were analysed for the production of TNF- and IL6 as indices for the activationof macrophages. The results show that the G. kola extract reduced the tendency of LPS to activate the cells. However, highest activation of LPS was observed when the cells were incubated with PMA for 48h prior to the addition of LPS. This suggests that stimulation of U937 cells with PMA is necessary for the production of cytokines and that G. kola possesses considerable immunomodulatory activity
