MPO and systemic lupus erythematosus: Notably, elimination of endosomal TLR signaling in multiple lupus-prone mouse strains, including BXSB, not only abolishes anti-nuclear IgG production and disease but also partially and significantly blocks production of antibodies to nonnuclear lupus-related autoantigens, including MPO, cardiolipin, and beta2-glycoprotein1 in MRL/lpr mice and red blood cells in NZB mice (61, 62).