The disease-protective complement factor H allotypic variant Ile62 shows increased binding affinity for C3b and enhanced cofactor activity

38 p.- 7 fig.Mutations and polymorphisms in the gene encoding factor H (CFH) have been associated with atypical haemolytic uraemic syndrome, dense deposit disease and age-related macular degeneration. The disease-predisposing CFH variants show a differential association with pathology that has been very useful to unravel critical events in the pathogenesis of one or other disease. In contrast, the factor H (fH)-Ile62 polymorphism confers strong protection to all three diseases. Using ELISA-based methods and surface plasmon resonance analyses, we show here that the protective fH-Ile62 variant binds more efficiently to C3b than fH-Val62 and competes better with factor B in proconvertase formation. Functional analyses demonstrate an increased cofactor activity for fH-Ile62 in the factor I-mediated cleavage of fluid phase and surface-bound C3b; however, the two fH variants show no differences in decay accelerating activity. From these data, we conclude that the protective effect of the fH-Ile62 variant is due to its better capacity to bind C3b, inhibit proconvertase formation and catalyze inactivation of fluid-phase and surface-bound C3b. This demonstration of the functional consequences of the fH-Ile62 polymorphism provides relevant insights into the complement regulatory activities of fH that will be useful in disease prediction and future development of effective therapeutics for disorders caused by complement dysregulationThis work was supported by MRC Project Grant Ref 84908 (to C.L.H. and B.P.M.), Ministerio de Ciencia e Innovación Ref SAF 2005-00913 (to S.R.deC.) the CIBER de Enfermedades Raras and Fundación Renal Iñigo Alvarez de Toledo (to S.R.deC.).Peer reviewe

Regulation of human CD4+ T cell differentiation

Naive CD4+ T cells differentiate into specific effector subsets—Th1, Th2, Th17, and T follicular helper (Tfh)—that provide immunity against pathogen infection. The signaling pathways involved in generating these effector cells are partially known. However, the effects of mutations underlying human primary immunodeficiencies on these processes, and how they compromise specific immune responses, remain unresolved. By studying individuals with mutations in key signaling pathways, we identified nonredundant pathways regulating human CD4+ T cell differentiation in vitro. IL12Rβ1/TYK2 and IFN-γR/STAT1 function in a feed-forward loop to induce Th1 cells, whereas IL-21/IL-21R/STAT3 signaling is required for Th17, Tfh, and IL-10–secreting cells. IL12Rβ1/TYK2 and NEMO are also required for Th17 induction. Strikingly, gain-of-function STAT1 mutations recapitulated the impact of dominant-negative STAT3 mutations on Tfh and Th17 cells, revealing a putative inhibitory effect of hypermorphic STAT1 over STAT3. These findings provide mechanistic insight into the requirements for human T cell effector function, and explain clinical manifestations of these immunodeficient conditions. Furthermore, they identify molecules that could be targeted to modulate CD4+ T cell effector function in the settings of infection, vaccination, or immune dysregulation

The Complement Factor H R1210C Mutation Is Associated With Atypical Hemolytic Uremic Syndrome

Mutations in the gene encoding complement factor H (CFH) that alter the C3b/polyanions-binding site in the C-terminal region impair the capacity of factor H to protect host cells. These mutations are also strongly associated with atypical hemolytic uremic syndrome (aHUS). Although most of the aHUS-associated CFH mutations seem “unique” to an individual patient or family, the R1210C mutation has been reported in several unrelated aHUS patients from distinct geographic origins. Five aHUS pedigrees and 7 individual aHUS patients were analyzed to identify potential correlations between the R1210C mutation and clinical phenotype and to characterize the origins of this mutation. The clinical phenotype of aHUS patients carrying the R1210C mutation was heterogeneous. Interestingly, 12 of the 13 affected patients carried at least one additional known genetic risk factor for aHUS. These data are in accord with the 30% penetrance of aHUS in R1210C mutation carriers, as it seems that the presence of other genetic or environmental risk factors significantly contribute to the manifestation and severity of aHUS in these subjects. Genotype analysis of CFH and CFHR3 polymorphisms in the 12 unrelated carriers suggested that the R1210C mutation has a single origin. In conclusion, the R1210C mutation of complement factor H is a prototypical aHUS mutation that is present as a rare polymorphism in geographically separated human populations

Partial IFN-gamma R2 deficiency is due to protein misfolding and can be rescued by inhibitors of glycosylation

WOS: 000326078200022PubMed ID: 23963039We report a molecular study of the two known patients with autosomal recessive, partial interferon-gamma receptor (IFN-gamma R)2 deficiency (homozygous for mutations R114C and G227R), and three novel, unrelated children, homozygous for S124F (P1) and G141R (P2 and P3). IFN-gamma R2 levels on the surface of the three latter patients' cells are slightly lower than those on control cells. The patients' cells also display impaired, but not abolished, response to IFN-gamma. Moreover, the R114C, S124F, G141R and G227R IFNGR2 hypomorphic alleles all encode misfolded proteins with abnormal N-glycosylation. The mutants are largely retained in the endoplasmic reticulum, although a small proportion reach and function at the cell surface. Strikingly, the IFN-gamma response of the patients' cells is enhanced by chemical modifiers of N-glycosylation, as previously shown for patients with gain-of-glysosylation T168N and misfolding 382-387dup null mutations. All four in-frame IFNGR2 hypomorphic mutant alleles encoding surface-expressed receptors are thus deleterious by a mechanism involving abnormal N-glycosylation and misfolding of the IFN-gamma R2 protein. The diagnosis of partial IFN-gamma R2 deficiency is clinically useful, as affected patients should be treated with IFN-, unlike patients with complete IFN-gamma R2 deficiency. Moreover, inhibitors of glycosylation might be beneficial in patients with complete or partial IFN-gamma R2 deficiency due to misfolding or gain-of-glycosylation receptors.European Research CouncilEuropean Research Council (ERC) [ERC-2010-AdG-268777]; Institut National de la Sante et de la Recherche Medicale, University Paris Descartes, French National Agency for Research (ANR)French National Research Agency (ANR); EUEuropean Union (EU) [HEALTH-F3-2008-200732]; Bill and Melinda Gates FoundationGates Foundation; St. Giles Foundation; Jeffrey Modell Foundation; Talecris Biotherapeutics; Rockefeller University Center for Clinical and Translational Science from the National Center for Research Resources and the National Center for Advancing Sciences (NCATS) [8UL1TR000043]; Rockefeller University; National Institute of Allergy and Infectious DiseasesUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Allergy & Infectious Diseases (NIAID) [1R01AI089970]; EMBO Long Term Fellowship program; Stony Wold-Herbert Fund; Choh-Hao Li Memorial Fund Scholar award; Shanghai Educational Development Foundation; AXA Research Fund; Fondation Medicale Medische Stichting Mathilde E. Horlait-DapsensThis work was supported by grants from the European Research Council (ERC-2010-AdG-268777), Institut National de la Sante et de la Recherche Medicale, University Paris Descartes, French National Agency for Research (ANR), the EU-grant HOMITB (grant HEALTH-F3-2008-200732), the Bill and Melinda Gates Foundation, the St. Giles Foundation, the Jeffrey Modell Foundation, and Talecris Biotherapeutics, Rockefeller University Center for Clinical and Translational Science grant 8UL1TR000043 from the National Center for Research Resources and the National Center for Advancing Sciences (NCATS), the Rockefeller University, and the National Institute of Allergy and Infectious Diseases (grant 1R01AI089970). R.M.-B. is supported by the EMBO Long Term Fellowship program. X.-F.K. is supported by the Stony Wold-Herbert Fund, Choh-Hao Li Memorial Fund Scholar award, and the Shanghai Educational Development Foundation, Y.I. was supported by the AXA Research Fund. V.L.B. was supported by the Stony Wold-Herbert Fund, and A.Y.K. was supported by the Fondation Medicale Medische Stichting Mathilde E. Horlait-Dapsens

Interleukin-23 receptor signaling impairs the stability and function of colonic regulatory T cells

The cytokine interleukin-23 (IL-23) is involved in the pathogenesis of inflammatory and autoimmune conditions including inflammatory bowel disease (IBD). IL23R is enriched in intestinal Tregs, yet whether IL-23 modulates intestinal Tregs remains unknown. Here, investigating IL-23R signaling in Tregs specifically, we show that colonic Tregs highly express Il23r compared with Tregs from other compartments and their frequency is reduced upon IL-23 administration and impairs Treg suppressive function. Similarly, colonic Treg frequency is increased in mice lacking Il23r specifically in Tregs and exhibits a competitive advantage over IL-23R-sufficient Tregs during inflammation. Finally, IL-23 antagonizes liver X receptor pathway, cellular cholesterol transporter Abca1, and increases Treg apoptosis. Our results show that IL-23R signaling regulates intestinal Tregs by increasing cell turnover, antagonizing suppression, and decreasing cholesterol efflux. These results suggest that IL-23 negatively regulates Tregs in the intestine with potential implications for promoting chronic inflammation in patients with IBD

The human gene damage index as a gene-level approach to prioritizing exome variants

The protein-coding exome of a patient with a monogenic disease contains about 20,000 variants, only one or two of which are disease causing. We found that 58% of rare variants in the protein-coding exome of the general population are located in only 2% of the genes. Prompted by this observation, we aimed to develop a gene-level approach for predicting whether a given human protein-coding gene is likely to harbor disease-causing mutations. To this end, we derived the gene damage index (GDI): a genome-wide, gene-level metric of the mutational damage that has accumulated in the general population. We found that the GDI was correlated with selective evolutionary pressure, protein complexity, coding sequence length, and the number of paralogs. We compared GDI with the leading gene-level approaches, genic intolerance, and de novo excess, and demonstrated that GDI performed best for the detection of false positives (i.e., removing exome variants in genes irrelevant to disease), whereas genic intolerance and de novo excess performed better for the detection of true positives (i.e., assessing de novo mutations in genes likely to be disease causing). The GDI server, data, and software are freely available to noncommercial users from lab.rockefeller.edu/casanova/GDI

Unique and shared signaling pathways cooperate to regulate the differentiation of human CD4⁺ T cells into distinct effector subsets

Naive CD4(+) T cells differentiate into specific effector subsets—Th1, Th2, Th17, and T follicular helper (Tfh)—that provide immunity against pathogen infection. The signaling pathways involved in generating these effector cells are partially known. However, the effects of mutations underlying human primary immunodeficiencies on these processes, and how they compromise specific immune responses, remain unresolved. By studying individuals with mutations in key signaling pathways, we identified nonredundant pathways regulating human CD4(+) T cell differentiation in vitro. IL12Rβ1/TYK2 and IFN-γR/STAT1 function in a feed-forward loop to induce Th1 cells, whereas IL-21/IL-21R/STAT3 signaling is required for Th17, Tfh, and IL-10–secreting cells. IL12Rβ1/TYK2 and NEMO are also required for Th17 induction. Strikingly, gain-of-function STAT1 mutations recapitulated the impact of dominant-negative STAT3 mutations on Tfh and Th17 cells, revealing a putative inhibitory effect of hypermorphic STAT1 over STAT3. These findings provide mechanistic insight into the requirements for human T cell effector function, and explain clinical manifestations of these immunodeficient conditions. Furthermore, they identify molecules that could be targeted to modulate CD4(+) T cell effector function in the settings of infection, vaccination, or immune dysregulation