Trevejo-Nunez et al. found that IL-22 systematically administered to S. pneumoniae-infected wild-type mice decreased bacterial load in the lung and liver 24 h post-infection by potentiating Complement component 3 (C3) opsonization on bacterial surfaces through the increase of hepatic C3 expression (Trevejo-Nunez et al., 2016). The gene discussed is C3; the disease is infection.