Impact of loss of NF-κB1, NF-κB2 or c-REL on SLE-like autoimmune disease and lymphadenopathy in Fas^lpr/lpr mutant mice

Defects in apoptosis can cause autoimmune disease. Loss-of-function mutations in the ‘death receptor’ FAS impair the deletion of autoreactive lymphocytes in the periphery, leading to progressive lymphadenopathy and systemic lupus erythematosus-like autoimmune disease in mice (Fas^lpr/lpr (mice homozygous for the lymphoproliferation inducing spontaneous mutation)) and humans. The REL/nuclear factor-κB (NF-κB) transcription factors regulate a broad range of immune effector functions and are also implicated in various autoimmune diseases. We generated compound mutant mice to investigate the individual functions of the NF-κB family members NF-κB1, NF-κB2 and c-REL in the various autoimmune pathologies of Fas^lpr/lpr mutant mice. We show that loss of each of these transcription factors resulted in amelioration of many classical features of autoimmune disease, including hypergammaglobulinaemia, anti-nuclear autoantibodies and autoantibodies against tissue-specific antigens. Remarkably, only c-REL deficiency substantially reduced immune complex-mediated glomerulonephritis and extended the lifespan of Fas^lpr/lpr mice. Interestingly, compared with the Fas^lpr/lpr animals, Fas^lpr/lprnfkb2^−/− mice presented with a dramatic acceleration and augmentation of lymphadenopathy that was accompanied by severe lung pathology due to extensive lymphocytic infiltration. The Fas^lpr/lprnfkb1^−/− mice exhibited the combined pathologies caused by defects in FAS-mediated apoptosis and premature ageing due to loss of NF-κB1. These findings demonstrate that different NF-κB family members exert distinct roles in the development of the diverse autoimmune and lymphoproliferative pathologies that arise in Fas^lpr/lpr mice, and suggest that pharmacological targeting of c-REL should be considered as a strategy for therapeutic intervention in autoimmune diseases.