TLR9 and systemic lupus erythematosus: While the reasons that underly the sex-biased role of Tlr7 in pSD are unknown, studies in the lupus field demonstrate that Tlr9 plays a key role in regulating Tlr7-driven immune activation, as Tlr9−/− lupus mice show exacerbated disease that is ameliorated when Tlr7 is also deleted (Nickerson et al., 2010).