Loss of c-REL but not NF- κ B2 prevents autoimmune disease driven by FasL mutation

FASL/FAS signaling imposes a critical barrier against autoimmune disease and lymphadenopathy. Mutant mice unable to produce membrane-bound FASL ( FasL Δ m/ Δ m ), a prerequisite for FAS-induced apoptosis, develop lymphadenopathy and systemic autoimmune disease with immune complex-mediated glomerulonephritis. Prior to disease onset, FasL Δ m/ Δ m mice contain abnormally high numbers of leukocytes displaying activated and elevated NF- κ B-regulated cytokine levels, indicating that NF- κ B-dependent inflammation may be a key pathological driver in this multifaceted autoimmune disease. We tested this hypothesis by genetically impairing canonical or non-canonical NF- κ B signaling in FasL Δ m/ Δ m mice by deleting the c-Rel or NF-κB2 genes, respectively. Although the loss of NF- κ B2 reduced the levels of inflammatory cytokines and autoantibodies, the impact on animal survival was minor due to substantially accelerated and exacerbated lymphoproliferative disease. In contrast, a marked increase in lifespan resulting from the loss of c-REL coincided with a striking reduction in classical parameters of autoimmune pathology, including the levels of cytokines and antinuclear autoantibodies. Notably, the decrease in regulatory T-cell numbers associated with loss of c-REL did not exacerbate autoimmunity in FasL Δ m/ Δ m c-rel −/− mice. These findings indicate that selective inhibition of c-REL may be an attractive strategy for the treatment of autoimmune pathologies driven by defects in FASL/FAS signaling that would be expected to circumvent many of the complications caused by pan-NF- κ B inhibition.