FAS and systemic lupus erythematosus: MRL/lpr are a Fas (CD95) gene-insertion model with defective lymphocyte apoptosis, massive lymphoproliferation, impaired autoreactive B-cell regulation, and high autoantibody titers.23 MRL/lpr mice develop NP manifestations early and are extensively used in lupus-related NP studies.13 We found that serum anti-dsDNA antibody (Ab, the typical serologic indicator of lupus) was evident by 8 weeks in MRL/lpr mice, with lupus nephritis onset at 18–20 weeks (Supplementary Fig. 1a).