Mice deficient in IL-17 are more susceptible to primary infection with F. holartica LVS, yet IL-17 is dispensable during secondary infection with either F. holartica LVS or F. tularensis (Woolard et al., 2008; Lin et al., 2009; Cowley et al., 2010; Markel et al., 2010; Skyberg et al., 2013; Roberts et al., 2014). The gene discussed is IL17A; the disease is infection.