Parasite burden at 24 h after exposure to C. parvum (a time point reflecting activating of the cellular defenses protecting against infection)16, as well as at 2 h after exposure to parasite (a time point reflecting the initial attachment and invasion of the parasite into host cells)16,28, was similar between IEC4.1 and IEC4.1-Ifnar1−/− cells (Fig. 1d). This evidence concerns the gene IFNAR1 and infection.