| The effects of fumonisin B1 (FB1) on the avian immune cell responses were investigated. Lymphocytes were collected from spleen, thymus and peripheral blood (PBL). Macrophages were collected from spleen and from the peritoneal cavity. The effects of varying concentrations of FB 1 (5 to 50 μg/ml) on lymphocyte viability, mitogenic response and macrophage activation were assessed using the MTT reduction assay. In addition, macrophage morphology, phagocytic ability and nitric oxide (NO) production were assessed in cells exposed to 5 to 50 μg/ml FB1. Finally, the effects of FB1 on induction of apoptosis and caspase-3 activity in splenocytes and thymocytes were investigated.; Fumonisin B1 decreased spleen cell viability, but had no effect on PBL viability. In thymocytes, an increase in viability was seen, however a statistical difference (P ≤ .05) was achieved only at the 50 μg/ml FB1. The effects of FB1 on the mitogenic response were evaluated in splenocytes and PBLs stimulated with the mitogens, lipopolysacchride (LPS), Concanavalin A (Con A) and Pokeweed mitogen (PWM) and thymocytes stimulated with Con A. Mitogenic response declined for all mitogens in FBI treated splenocytes; albeit, the degree of decrease varied with mitogen and time of exposure. No effect on mitogenic response was observed in FBI treated cells from the thymus or PBL.; Fumonisin B1 decreased cell activity in macrophages recruited from the peritoneum, yet increased the splenic macrophage activity. Nitric oxide production increased in all macrophage populations investigation, such that at 50 μg/ml FB1 NO production was increased approximately 2-fold in all cells. Finally, FB1 caused an increase in vacuolization in macrophages and decreased the ability of the cells to uptake sheep red blood cells.; The effects of FB1 on apoptosis processes were investigated as well. Agarose gel electrophoresis showed FB1 induced apoptosis in splenocytes. Fumonisin B1 did not effect caspase-3 activity within these cells, whereas, caspase-3 activity increased in thymocytes exposed to FB1. Through the use of exogenous sphingosine and the serine palmitoyltransferase inhibitor, myriocin, it was shown that the induction of caspase is probably associated to the increase in sphingosine induced by FB1. |
