IFNG and infection: As outlined above, infection with B. pertussis naturally induces a significant Th1-type T-lymphocyte cytokine response in mice that is characterized by high levels of IL-2, IFN-γ, and TNF-α, a type of immune response that is characteristic of infection by intracellular pathogens (Spellberg and Edwards, 2001; Thakur et al., 2019).