We have shown before that there is a positive correlation between resistance of cattle against Cowdria infection and early IFN production. Our in vitro studies demonstrated an activity of rBoIFN alpha 2C and rBoIFN gamma against Cowdria in bovine endothelial cells of brain microvasculature (BMEC). rBoIFN gamma is much more active in this respect than rBoIFN alpha 2C. These results suggest a role of IFNs in the resistance against the disease. Strikingly, in the same conditions rBoIFN alpha 2C has no effect on the yield of Cowdria from infected bovine endothelial cells of umbilical artery origin (BUEC). Similarly we showed that HuIFNa had no effect on the multiplication of Cowdria in human vein umbilical endothelial cells (HUVEC). We found no differences in the capacity of BUE and BME cells to bind rBoIFN alpha 2C. This may reflect a true difference between capillary and large blood vessels.