Suchergebnisse

16 p.-9 fig. ; Complement activation on cell surfaces leads to the massive deposition of C3b, iC3b, and C3dg, the main complement opsonins. Recognition of iC3b by complement receptor type 3 (CR3) fosters pathogen opsonophagocytosis by macrophages and the stimulation of adaptive immunity by complement-opsonized antigens. Here, we present the crystallographic structure of the complex between human iC3b and the von Willebrand A inserted domain of the α chain of CR3 (αI). The crystal contains two composite interfaces for CR3 αI, encompassing distinct sets of contiguous macroglobulin (MG) domains on the C3c moiety, MG1-MG2 and MG6-MG7 domains. These composite binding sites define two iC3b-CR3 αI complexes characterized by specific rearrangements of the two semi-independent modules, C3c moiety and TED domain. Furthermore, we show the structure of iC3b in a physiologically-relevant extended conformation. Based on previously available data and novel insights reported herein, we propose an integrative model that reconciles conflicting facts about iC3b structure and function and explains the molecular basis for iC3b selective recognition by CR3 on opsonized surfaces. ; This work was funded by Spanish Ministerio de Ciencia, Innovación y Universidades-FEDER grant RTI2018-102242-B-I00 (to M.C.V.) and PID2019-104912RB-I00 (to S.R.C.), and Spanish Ministerio de Economía y Competitividad-FEDER grants SAF2015-72961-EXP (to M.C.V.) and SAF2015-66287-R (to S.R.C.). It was also funded by Grant S2017/BMD-3673 of the Regional Government of Madrid and the European Commission – NextGenerationEU through CSIC's Global Health Platform ("PTI Salud Global") (SGL2103020) (to S.R.C. and M.C.V.), and the CSIC Special Intramural Grant PIE-201620E064 (to M.C.V.). It was additionally supported by the Network of Excellence Complement in Health and Disease (SAF2016-81876-REDT). SRC was also supported by the CIBER de Enfermedades Raras. JSL acknowledges the support of the PhD program in Molecular Biosciences of the Universidad Autónoma de Madrid (UAM) and the Ministry of Education, Culture and Sports of Spain (FPU Grant 17/06090). SNY acknowledges the support of the PhD program in Biochemistry, Molecular Biology and Biomedicine of the Universidad Complutense de Madrid (UCM). ; Peer reviewed

14 p.-7 fig.-2 tab. ; Complement overactivation has been reported in most patients with Barraquer–Simons syndrome (BSS), a rare form of acquired partial lipodystrophy. Complement Factor D (FD) is a serine protease with a crucial role in the activation of the alternative pathway of the complement system, which is mainly synthesized by adipose tissue. However, its role in the pathogenesis of BSS has not been addressed. In this study, plasma FD concentration was measured in 13 patients with BSS, 20 patients with acquired generalized lipodystrophy, 22 patients with C3 glomerulopathy (C3G), and 50 healthy controls. Gene expression and immunohistochemistry studies were assayed using atrophied adipose tissue from a patient with BSS. We found significantly elevated FD levels in BSS cases compared with the remaining cohorts (p < 0.001). There were no significant differences in FD levels between sexes but FD was strongly and directly associated with age in BSS (r = 0.7593, p = 0.0036). A positive correlation between FD and C3 was seen in patients with C3G, characterized by decreased FD levels due to chronic C3 consumption, but no correlation was detected for BSS. Following mRNA quantification in the patient's adipose tissue, we observed decreased CFD and C3 but elevated C5 transcript levels. In contrast, the increased FD staining detected in the atrophied areas reflects the effects of persistent tissue damage on the adipose tissue, thus providing information on the ongoing pathogenic process. Our results suggest that FD could be a reliable diagnostic biomarker involved in the pathophysiology of BSS by promoting unrestrained local complement system activation in the adipose tissue environment. ; This study was funded by the Spanish Instituto de Salud Carlos III (ISCIII) and the European Regional Development Fund from the European Union (grant PI15-00255), by the Spanish Autonomous Region of Madrid (Complement II-CM network; S2017/BMD-3673), by the Asociación Española de Familiares y Afectados de Lipodistrofias (AELIP), by an intramural grant from the Xunta de Galicia (grant number ED431B 2020/37), and by the intramural research program of the National Institute of Diabetes and Digestive and Kidney Diseases. ; Peer reviewed

Complement overactivation has been reported in most patients with Barraquer–Simons syndrome (BSS), a rare form of acquired partial lipodystrophy. Complement Factor D (FD) is a serine protease with a crucial role in the activation of the alternative pathway of the complement system, which is mainly synthesized by adipose tissue. However, its role in the pathogenesis of BSS has not been addressed. In this study, plasma FD concentration was measured in 13 patients with BSS, 20 patients with acquired generalized lipodystrophy, 22 patients with C3 glomerulopathy (C3G), and 50 healthy controls. Gene expression and immunohistochemistry studies were assayed using atrophied adipose tissue from a patient with BSS. We found significantly elevated FD levels in BSS cases compared with the remaining cohorts (p < 0.001). There were no significant differences in FD levels between sexes but FD was strongly and directly associated with age in BSS (r = 0.7593, p = 0.0036). A positive correlation between FD and C3 was seen in patients with C3G, characterized by decreased FD levels due to chronic C3 consumption, but no correlation was detected for BSS. Following mRNA quantification in the patient's adipose tissue, we observed decreased CFD and C3 but elevated C5 transcript levels. In contrast, the increased FD staining detected in the atrophied areas reflects the effects of persistent tissue damage on the adipose tissue, thus providing information on the ongoing pathogenic process. Our results suggest that FD could be a reliable diagnostic biomarker involved in the pathophysiology of BSS by promoting unrestrained local complement system activation in the adipose tissue environment. ; This study was funded by the Spanish Instituto de Salud Carlos III (ISCIII) and the European Regional Development Fund from the European Union (grant PI15-00255), by the Spanish Autonomous Region of Madrid (Complement II-CM network; S2017/BMD-3673), by the Asociación Española de Familiares y Afectados de Lipodistrofias (AELIP), by an intramural grant from the Xunta de Galicia (grant number ED431B 2020/37), and by the intramural research program of the National Institute of Diabetes and Digestive and Kidney Diseases

34 p.-2 fig.-3 tab. ; Pregnancy-associated atypical hemolytic uremic syndrome (aHUS) refers to the thrombotic microangiopathy resulting from uncontrolled complement activation during pregnancy or the postpartum period. Pregnancy-associated aHUS is a devastating disease for which there is a limited clinical understanding and treatment experience. Here we report a retrospective study to analyze the clinical and prognostic data of 22 cases of pregnancy-associated aHUS from the Spanish aHUS Registry under different treatments. Sixteen patients presented during the first pregnancy and as many as nine patients required hemodialysis at diagnosis. Identification of inherited complement abnormalities explained nine of the 22 cases, with CFH mutations and CFH to CFHR1 gene conversion events being the most prevalent genetic alterations associated with this disorder (66%). In thirteen of the cases, pregnancy complications were sufficient to trigger a thrombotic microangiopathy in the absence of genetic or acquired complement alterations. The postpartum period was the time with highest risk to develop the disease and the group shows an association of cesarean section with pregnancy-associated aHUS. Seventeen patients underwent plasma treatments with a positive renal response in only three cases. In contrast, ten patients received eculizumab with an excellent renal response in all, independent of carrying or not inherited complement abnormalities. Although the cohort is relatively small, the data suggest that pregnancy-associated aHUS is not different from other types of aHUS and suggest the efficacy of eculizumab treatment over plasma therapies. This study may be useful to improve prognosis in this group of aHUS patients. ; Work in this report was funded by the Instituto de Salud Carlos III: REDinREN (RD016/009 and RD012/0021) and Fondo de Investigaciones Sanitarias (ISCIII/FEDER) ref 13/02502 and ref 16/01685. SRdeC is supported by the Spanish "Ministerio de Economía y Competitividad-FEDER" (SAF2015-66287R), the Seventh Framework Programme European Union Project EURenOmics (305608) and the Autonomous Region of Madrid (S2010/BMD-2316). ; Peer reviewed

Background. Complement dysregulation occurs in thrombotic microangiopathies (TMAs) other than primary atypical haemolytic uraemic syndrome (aHUS). A few of these patients have been reported previously to be successfully treated with eculizumab. Methods. We identified 29 patients with so-called secondary aHUS who had received eculizumab at 11 Spanish nephrology centres. Primary outcome was TMA resolution, defined by a normalization of platelet count (>150 × 109/L) and haemoglobin, disappearance of all the markers of microangiopathic haemolytic anaemia (MAHA), and improvement of renal function, with a ≥25% reduction of serum creatinine from the onset of eculizumab administration. Results. Twenty-nine patients with secondary aHUS (15 drug-induced, 8 associated with systemic diseases, 2 with postpartum, 2 with cancer-related, 1 associated with acute humoral rejection and 1 with intestinal lymphangiectasia) were included in this study. The reason to initiate eculizumab treatment was worsening of renal function and persistence of TMA despite treatment of the TMA cause and plasmapheresis. All patients showed severe MAHA and renal function impairment (14 requiring dialysis) prior to eculizumab treatment and 11 presented severe extrarenal manifestations. A rapid resolution of the TMA was observed in 20 patients (68%), 15 of them showing a ≥50% serum creatinine reduction at the last follow-up. Comprehensive genetic and molecular studies in 22 patients identified complement pathogenic variants in only 2 patients. With these two exceptions, eculizumab was discontinued, after a median of 8 weeks of treatment, without the occurrence of aHUS relapses. Conclusion. Short treatment with eculizumab can result in a rapid improvement of patients with secondary aHUS in whom TMA has persisted and renal function worsened despite treatment of the TMA-inducing condition ; Work in this report was funded by the Instituto de Salud Carlos III: REDinREN (RD 016/009 Feder Funds), the Fondo de Investigaciones Sanitarias (13/02502 and ICI14/00350), the Ministerio de Economia y Competitividad (SAF2015-66287R) and the Autonomous Region of Madrid (S2010/BMD-2316; Grupo de Investigación Complemento-CM). SRdeC is funded by the Seventh Framework Programme European Union Project EURenOmics (305608)