A significant role for tumor necrosis factor in Nlrp3 inflammasomeopathies

Results Nearly all FCAS Il1bIl18-/-mice survived and grew normally until adulthood however, investigation of mice at > 6 months of age showed marked splenomegaly and elevated numbers of white blood cells as compared to FCAS Casp1 mice and non-mutant Il1bIl18-/-littermates, suggesting a caspase-1 dependent phenotype independent of IL-1b and IL-18. To examine other potential inflammatory mediators, non-lethal in vivo LPS (5 ug/g) stimulation of FCAS Il1b Il18mice revealed significantly elevated levels of serum TNF at both 2 and 6 hours post induction when compared to FCAS Casp1mice and non-mutant Il1bIl18-/-controls. To further investigate the role of TNF in Nlrp3 inflammasomeopathies, MWS mice (which die within two weeks of birth) were bred on a TNF knockout background. MWS Tnf pups were indistinguishable from non-mutant controls with all animals surviving to adulthood with normalization of both body and spleen/body weight comparisons. Serum analysis of MWS Tnf pups showed attenuation of NLRP3 inflammsome related cytokines when compared to intact MWS pups. The skin of intact MWS pups exhibited strong neutrophilic and inflammatory macrophage infiltrations, which were normalized in MWS Tnf animals. Interestingly, MWS Tnf +/pups also showed an intermediate protective effect on all of the aforementioned comparisons. To determine if TNF ablation could be recapitulated with therapeutic intervention, MWS pups were treated with recombinant soluble TNF receptor (Etanercept 400ug/g sc EOD). Treatment provided similar phenotypic rescue and extended survival for an average of 22 days after cessation of treatment. Adult MWS Tnf mice at > 6 months of age were found to have splenomegaly and elevated numbers of white blood cells when compared to non-mutant Tnf littermates, implicating a role for other inflammatory mechanisms as mice age.