ARG1 and infection: The transcription of the iNOS gene increased upon infection and reached its highest level at the 6th week post-infection, then decreased; while the Arginase-1 started to increase in the 3rd week and reached the highest level at the endpoint of the 12th week post-infection (Figure 1e), further suggesting that adult C. hepatica worms stimulated the M1 macrophages, while the eggs boosted the M2 macrophages in the infected liver tissue.