Mitogens known to cause optimal IFN-γ release independent of the host’s infection status are used as positive controls in the IFN-γ assay, but the mitogen’s efficacy might also be species specific (Angkawanish et al. 2013; Maas et al. 2012; Morar et al. 2013; Schiller et al. 2009). Here, IFNG is linked to infection.