Introduction Familial Mediterranean fever (FMF) is a genetic disease leading to recurrent episodes of inflammation. Two pathogenic variants are required for classical disease, but the disease can occur in heterozygous patients. Patients are treated continuously with colchicine to prevent amyloid A (AA) amyloidosis, including heterozygous patients who display a moderate form of FMF and rarely develop AA amyloidosis. The need for lifelong colchicine treatment in heterozygous FMF is therefore controversial. We aimed to characterise genotype-specific levels of inflammatory biomarkers, and to focus on heterozygous patients who discontinued colchicine. Methods All patients with FMF from the European databases AIDnet and JIRcohort who received colchicine during follow-up were included. Demographics, C reactive protein (CRP), serum amyloid A (SAA), S100A8/A9 and S100A12 levels, leucocyte and neutrophil counts were extracted. Visits were classified as active, subclinical or inactive according to symptoms, CRP and SAA levels. Results Data from 747 patients were extracted (233 homozygous, 201 compound heterozygous, 224 heterozygous patients, 49 heterozygous with one class III variant and 40 compound heterozygous with two class III variants). During active visits, all biomarker levels were higher compared with inactive visits (p<0.001). Heterozygous patients showed lower levels of CRP, SAA, S100A8/A9 and S100A12 during inactive and subclinical visits than patients with two class IV-V variants. Colchicine was discontinued in 52 heterozygous patients and reintroduced in 23 of them (44%). Conclusion S100A8/A9 and S100A12 proteins are biomarkers that can be used to assess disease activity. Heterozygous patients have lower levels of inflammatory biomarkers and some of them can sustainably discontinue colchicine treatment.

Systemic juvenile idiopathic arthritis (SJIA) is a severe rheumatic disease in children. It is a subgroup of juvenile idiopathic arthritis (JIA; MIM #604302), which is the most common rheumatic disease in children. The diagnosis of SJIA often comes with a significant delay, and the classification between autoinflammatory and autoimmune disease is still discussed. In this study, we analyzed the immunological responses of patients with SJIA, using human proteome arrays presenting immobilized recombinantly expressed human proteins, to analyze the involvement of autoantibodies in SJIA. Results from group comparisons show several differentially reactive antigens involved in inflammatory processes. Intriguingly, many of the identified antigens had a high reactivity against proteins involved in the NF-$\kappa$B pathway, and it is also notable that many of the detected DIRAGs are described as dysregulated in rheumatoid arthritis. Our data highlight novel proteins and pathways potentially dysregulated in SJIA and offer a unique approach to unraveling the underlying disease pathogenesis in this chronic arthropathy.

In this protocol, we describe a method to purify human calcium-binding protein S100A12 and its ion-induced oligomers from Escherichia coli culture for immune cell stimulations. This protocol is based on a two-step chromatography strategy, which comprises protein pre-purification on an anion-exchange chromatography column and a subsequent polishing step on a hydrophobic-interaction column. This strategy produces S100A12 protein of high purity and yield at manageable costs. For functional assays on immune cells eventual remnant endotoxin contamination requires careful monitoring and further cleaning steps to obtain endotoxin-free protein. The majority of endotoxin contaminations can be excluded by anion-exchange chromatography. To deplete residual contaminations, this protocol describes a removal step with centrifugal filters. Depending on the available ion-strength S100A12 can arrange into different homomultimers. To investigate the relationship between structure and function, this protocol further describes ion-treatment of S100A12 protein followed by chemical crosslinking to stabilize S100A12 oligomers and their subsequent separation by size-exclusion chromatography. Finally, we describe a cell-based assay that confirms the biological activity of the purified protein and confirms LPS-free preparation.