IFNG and infection: In our study, the amount of IFN-γ in plasma increased significantly at 21 days post-infection for the German Landrace pigs, in correlation with the highest susceptibility to infection, whereas the plasma samples from Hampshire pigs, the most resistant to infection, did not show any increase and the amounts of IFN-γ were lower than those from German Landrace, Pietrain and Large White pigs.