IFNG and infection: The results presented here thus argue in favour of two opposite roles played by IFN-γ during P. yoelii primary infection in B6 mice: in the first days following sporozoites injection, IFN-γ would be deleterious for the host as it favours the parasitaemia, while, after the first week of infection, it would be beneficial for the host, helping to clear efficiently the blood-stage parasites.