IFNAR1 and infection: We further compared the roles of RickA and Sca2 in vivo following intradermal (i.d.)infection of Ifnar1−/−; Ifngr1−/− mice carrying knockout mutations in the genes encoding the receptors for IFN-I (Ifnar1) and IFN-γ (Ifngr1), which exhibit eschars and succumb to infection with wild-type (WT) R. parkeri.