B6/lpr-p2x7KO mice accumulated high numbers of FasL-expressing B220+ DN T cells of CD45RBhighCD44high effector/memory CD8+ T-cell origin and developed severe lupus, characterized by leukocyte infiltration into the tissues, high levels of IgG anti-dsDNA and rheumatoid factor autoantibodies, and marked cytokine network dysregulation. The gene discussed is FASLG; the disease is systemic lupus erythematosus.