Related Articles Monocyte-derived dendritic cells display a highly activated phenotype and altered function in patients with familial Mediterranean fever. Clin Exp Immunol. 2020 07;201(1):1-11 Authors: Funk T, Fuchs AR, Altdörfer VS, Klein R, Autenrieth SE, Müller MR, Salih HR, Henes J, Grünebach F, Dörfel D Abstract Dendritic cells (DCs) are sentinels of the immune system that bridge innate and adaptive immunity. By capturing antigens in peripheral tissue, processing and presenting them with concurrent expression of co-stimulatory molecules and cytokine secretion they control and modulate immune reactions. Through pattern recognition receptors, DCs sense molecules that are associated with infection or tissue damage, frequently resulting in the formation of inflammasomes upon intracellular stimulation. The inherited autoinflammatory familial Mediterranean fever (FMF) is associated with deregulated activity of the pyrin inflammasome leading to acute inflammatory episodes. However, differentiation and function of DCs in this disease are as yet unclear. Therefore, we first determined DC subpopulation frequency in peripheral blood of a cohort of FMF patients. Joint evaluation without classification according to specific patient characteristics, such as mutational status, did not disclose significant differences compared to healthy controls. For the further examination of phenotype and function, we used immature and mature monocyte-derived DCs (imMo-DCs, mMo-DCs) that were generated in vitro from FMF patients. Immunophenotypical analysis of imMo-DCs revealed a significantly elevated expression of CD83, CD86 and human leukocyte antigen D-related (HLA-DR) as well as a significant down-regulation of CD206, CD209 and glycoprotein NMB (GPNMB) in our FMF patient group. Furthermore, FMF imMo-DCs presented a significantly higher capacity to migrate and to stimulate the proliferation of unmatched allogeneic T cells. Finally, the transition towards a more mature, and therefore activated, phenotype was additionally reinforced by the fact that peripheral blood DC populations in FMF patients exhibited significantly increased expression of the co-stimulatory molecule CD86. PMID: 32278322 [PubMed - indexed for MEDLINE]

Related Articles The Pyrin Inflammasome in Health and Disease. Front Immunol. 2019;10:1745 Authors: Schnappauf O, Chae JJ, Kastner DL, Aksentijevich I Abstract The pyrin inflammasome has evolved as an innate immune sensor to detect bacterial toxin-induced Rho guanosine triphosphatase (Rho GTPase)-inactivation, a process that is similar to the "guard" mechanism in plants. Rho GTPases act as molecular switches to regulate a variety of signal transduction pathways including cytoskeletal organization. Pathogens can modulate Rho GTPase activity to suppress host immune responses such as phagocytosis. Pyrin is encoded by MEFV, the gene that is mutated in patients with familial Mediterranean fever (FMF). FMF is the prototypic autoinflammatory disease characterized by recurring short episodes of systemic inflammation and is a common disorder in many populations in the Mediterranean basin. Pyrin specifically senses modifications in the activity of the small GTPase RhoA, which binds to many effector proteins including the serine/threonine-protein kinases PKN1 and PKN2 and actin-binding proteins. RhoA activation leads to PKN-mediated phosphorylation-dependent pyrin inhibition. Conversely, pathogen virulence factors downregulate RhoA activity in a variety of ways, and these changes are detected by the pyrin inflammasome irrespective of the type of modifications. MEFV pathogenic variants favor the active state of pyrin and elicit proinflammatory cytokine release and pyroptosis. They can be inherited either as a dominant or recessive trait depending on the variant's location and effect on the protein function. Mutations in the C-terminal B30.2 domain are usually considered recessive, although heterozygotes may manifest a biochemical or even a clinical phenotype. These variants are hypomorphic in regard to their effect on intramolecular interactions, but ultimately accentuate pyrin activity. Heterozygous mutations in other domains of pyrin affect residues critical for inhibition or protein oligomerization, and lead to constitutively active inflammasome. In healthy carriers of FMF mutations who have the subclinical inflammatory phenotype, the increased activity of pyrin might have been protective against endemic infections over human history. This finding is supported by the observation of high carrier frequencies of FMF-mutations in multiple populations. The pyrin inflammasome also plays a role in mediating inflammation in other autoinflammatory diseases linked to dysregulation in the actin polymerization pathway. Therefore, the assembly of the pyrin inflammasome is initiated in response to fluctuations in cytoplasmic homeostasis and perturbations in cytoskeletal dynamics. PMID: 31456795 [PubMed - indexed for MEDLINE]

Related Articles Late-onset familial Mediterranean fever in Japan. Mod Rheumatol. 2020 May;30(3):564-567 Authors: Kishida D, Yazaki M, Nakamura A, Tsuchiya-Suzuki A, Shimojima Y, Sekijima Y Abstract Objectives: Most patients with familial Mediterranean fever (FMF) have their first attack at age < 20 years. Information about late-onset (age ≥40 years) FMF is limited. We aimed to evaluate the demographic, clinical, and genetic characteristics of late-onset FMF patients in the Japanese population.Methods: We retrospectively analyzed 292 patients with FMF. Patients were divided into three groups according to age of disease onset: Group I, ≤19 years; Group II, 20-39 years; and Group III, ≥40 years.Results: Of 292 patients, 44 (15.1%) experienced their first attack at age ≥40 years. While high fever (97.7%) and arthritis (45.5%) were common symptoms in Group III patients, peritonitis (40.9%) and pleuritis (25.0%) were significantly lower than in other groups. The frequency of patients carrying p.M694I (18.2%), which is the most representative mutation in Japan, was significantly lower in Group III than in Group I. The response to colchicine therapy was good (95.1%) and similar in all groups.Conclusions: In Japan, more patients than expected had late-onset FMF. They had a milder form of disease, with less frequent peritonitis and pleuritis. The response to colchicine treatment was good. Clinicians should consider FMF for patients with unexplained recurrent febrile episodes, regardless of age. PMID: 31116049 [PubMed - indexed for MEDLINE]