Supporting a potential protective role, the type I IFN-inducible gene Isg15, which showed much greater induction of expression in C57BL/6 than C3HeB/FeJ mice at 14 days after infection (Fig. 7, c and d; and Fig. S5 a), has been implicated in promoting the protective IFN-γ response to mycobacteria (Bogunovic et al., 2012), and type I IFN signaling offers protection against M. tuberculosis in mice lacking IFN-γ signaling (Moreira-Teixeira et al., 2016). Here, ISG15 is linked to infection.