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BackgroundMannose-binding lectin (MBL) encoded by MBL2 gene is a protein with the ability to form carbohydrate complexes with microbial wall promoting their subsequent elimination. Genetically determined levels of MBL can modify the risk and clinical characteristics of many infectious diseases. The frequency of MBL2 genotypes exhibits significant population differences. The data on the distribution of MBL2 genotypes among the aborigines of the Russian Arctic territories have not yet been published.MethodsA total of 880 specimens of dried blood spots of the newborns were genotyped. The newborns represented four populations: Nenets, Dolgan-Nganasans, Mixed aboriginal population, and Russians (Caucasians, Krasnoyarsk). Six polymorphisms of the MBL2 gene were studied: rs11003125, rs7096206, rs7095891, rs5030737, rs1800450, and rs1800451.ResultsThe frequency of the combined rare O allele (composed of the coding region variants rs5030737, rs1800450, and rs1800451) in the homozygous state was significantly higher in Russians: 10% vs 2% in Nenets and 1% in Dolgan-Nganosans (pConclusionOur study results are in line with the hypothesis that human evolution has been moving in the direction of accumulation of the genotypes associated with low activity of the lectin complement activation pathway because of the prevalence of some intracellular infections such as tuberculosis, whereby low MBL activity may have a protective effect.

Plant lectins are carbohydrate-binding proteins with nonimmune origin, which can reversibly bind with carbohydrates, agglutinate cells, and precipitate polysaccharides and glycoconjugates. Plant lectins have attracted much attention for their anti-virus, anti-proliferation, and pro-apoptosis properties. Thus the exploration of new lectins has received special attention. Here we purified a mannose-binding lectin from the rhizomes of Liparis nervosa by ion exchange chromatography on DEAE-Sepharose, affinity chromatography on Mannose-Sepharose 4B, and gel filtration chromatography on Sephacryl S-100. The purified L. nervosa lectin (LNL) was identified to be a monomeric protein with a molecular mass of 13 kDa. LNL exhibited hemagglutinating activity towards rabbit erythrocytes, and its activity could be strongly inhibited by D-mannose, N-acetyl glucosamine and thyroglobulin. In vitro experiments showed that LNL exhibited a comparable anti-fungal activity against Piricularia oryzae (Cavara), Bipolaris maydis, Fusarium graminearum, and Sclerotium rolfsii, and anti-proliferation activity against tumor cells by inducing apoptosis. The full-length cDNA sequence of LNL is 715 bp in length and contains a 525 bp open reading frame (ORF) encoding a 110-residue mature protein. It was predicted to have three mannose-binding conserved motifs 'QXDXNXVXY'. The binding pattern of LNL was further revealed by homology modeling and molecular docking. We demonstrated that LNL is not only a potential therapeutic candidate against tumor but also a new anti-fungal agent.

C-type lectins that contain collagen-like domains are known as collectins. These proteins are present both in the circulation and in extravascular compartments and are central players of the innate immune system, contributing to first-line defenses against viral, bacterial, and fungal pathogens. The collectins mannose-binding lectin (MBL) and surfactant protein D (SP-D) are regulated by tissue fibroblasts at extravascular sites via an endocytic mechanism governed by urokinase plasminogen activator receptor–associated protein (uPARAP or Endo180), which is also a collagen receptor. Here, we investigated the molecular mechanisms that drive the uPARAP-mediated cellular uptake of MBL and SP-D. We found that the uptake depends on residues within a protruding loop in the fibronectin type-II (FNII) domain of uPARAP that are also critical for collagen uptake. Importantly, however, we also identified FNII domain residues having an exclusive role in collectin uptake. We noted that these residues are absent in the related collagen receptor, the mannose receptor (MR or CD206), which consistently does not interact with collectins. We also show that the second C-type lectin-like domain (CTLD2) is critical for the uptake of SP-D, but not MBL, indicating an additional level of complexity in the interactions between collectins and uPARAP. Finally, we demonstrate that the same molecular mechanisms enable uPARAP to engage MBL immobilized on the surface of pathogens, thereby expanding the potential biological implications of this interaction. Our study reveals molecular details of the receptor-mediated cellular regulation of collectins and offers critical clues for future investigations into collectin biology and pathology.

An insecticidal mannose binding lectin gene of Withania somnifera, WsMBP1 was constitutively expressed in tobacco plants. Instar-wise study on the response of Hyblaea puera larvae to the total protein extracted from transgenic tobacco was conducted and survivability percent was 33.33% and 55.55% in the first and the second instars, respectively. Minimum survivability of 22.22% was registered in the third instar. Further, two-fold reduction was observed in mean pre-pupal and pupal weight in the third instar larval populations fed with lectin protein compared to the control populations. The functional confirmation of the insecticidal activity of WsMBP1 established its potential as a novel gene resource for future transformation studies in developing teak genotypes tolerant to its leaf defoliator, H. puera.

We investigated clinical associations of ficolins and mannose-binding lectin (MBL) in 157 patients suffering from acute myeloid leukaemia (AML). Concentrations of ficolin-1, ficolin-2, ficolin-3 and MBL (before chemotherapy) in serum were determined as were selected polymorphisms of the corresponding genes (FCN1, FCN2, FCN3 and MBL2). The control group (C) consisted of 267 healthy unrelated individuals. Median level of ficolin-1 in patients was lower (p p p p = 0.0016, respectively) compared with controls. These findings were generally associated with AML itself, however the highest MBL levels predicted higher risk of severe hospital infections (accompanied with bacteremia and/or fungaemia) (p = 0.012) while the lowest ficolin-1 concentrations tended to be associated with prolonged (> 7 days) fever (p = 0.026). Genotyping indicated an association of G/G homozygosity (corresponding to FCN1 gene − 542 G > A polymorphism) with malignancy [p = 0.004, OR = 2.95, 95% CI (1.41–6.16)]. Based on ROC analysis, ficolin-1, -2 and -3 may be considered candidate supplementary biomarkers of AML. Their high potential to differentiate between patients from non-malignant controls but also from persons suffering from other haematological cancers (multiple myeloma and lymphoma) was demonstrated.

Mannose-binding lectin (MBL) deficiency is associated with recurrent infections, autoimmune and inflammatory skin disease, and vascular complications. MBL deficiency is not a recognized comorbidity in hidradenitis suppurativa (HS); the latter is associated with the group of autoinflammatory disorders. A 32-year-old woman presented with a history of recurrent painful, deep-seated abscesses and pustular lesions since the age of 13 years. Lesions were noted predominantly in HS distribution, i.e., submammary, inguinal, and perianal areas were affected. However, unusual locations (jawlines, neck) were also affected. The patient fulfilled the clinical criteria for HS but the presentation was atypical because lesions were noted in unusual locations, most lesions were in Hurley stage 1 (sparsity of sinus tracts and scarring), and most cultures from abscesses and pustular lesions were negative. The excruciating pain caused by constantly developing abscesses had a profound impact on the patient’s quality of life. Laboratory workup showed an exceptionally low serum MBL level. Treatment was challenging with only a temporary, mild response to oral antibiotic therapy and no response to immunosuppressive and hormonal therapies. This atypical HS presentation may reflect an enhancement of proinflammatory mechanisms. Health care providers should be aware of this clinicopathologic presentation so that the establishment of HS diagnosis is not delayed and the patient receives appropriate counseling.

To evaluate the complement related pattern recognition molecules (PRMs) PTX3, MBL, CL-11, ficolin-2 and -3, along with the established marker CRP, to predict 28-day mortality and disease severity of sepsis in patients admitted to the intensive care unit (ICU).In a single-center, prospective, observational study 547 patients were included over a period of 18 months. Blood samples were obtained at admission to the ICU and the following 4 days.PTX3 baseline levels were significantly higher in non-survivors compared to survivors, whereas MBL and ficolin-2 levels were significantly lower in non-survivors compared to survivors. A PTX3 level above the median was independently associated with 28-day mortality in the adjusted analysis including age, sex, chronic disease and immunosuppression (HR 1.87, 95% CI [1.41-2.48], p 0.0001), while a MBL level above the median was associated with increased chance of survival (HR 0.75, 95% CI [0.57-0.98], p = 0.034). Ficolin-2 was only borderline significant (HR 0.79, 95% CI [0.60-1.03], p = 0.084). In a ROC analysis PTX3 was superior to CRP in predicting septic shock.PTX3, MBL and CRP levels were independently associated with 28-day mortality in ICU patients. PTX3 was a better marker of septic shock compared to CRP.

This guideline aims to describe the complement system and the functions of the constituent pathways, with particular focus on primary immunodeficiencies (PIDs) and their diagnosis and management. The complement system is a crucial part of the innate immune system, with multiple membrane-bound and soluble components. There are three distinct enzymatic cascade pathways within the complement system, the classical, alternative and lectin pathways, which converge with the cleavage of central C3. Complement deficiencies account for ~5% of PIDs. The clinical consequences of inherited defects in the complement system are protean and include increased susceptibility to infection, autoimmune diseases (e.g., systemic lupus erythematosus), age-related macular degeneration, renal disorders (e.g., atypical hemolytic uremic syndrome) and angioedema. Modern complement analysis allows an in-depth insight into the functional and molecular basis of nearly all complement deficiencies. However, therapeutic options remain relatively limited for the majority of complement deficiencies with the exception of hereditary angioedema and inhibition of an overactivated complement system in regulation defects. Current management strategies for complement disorders associated with infection include education, family testing, vaccinations, antibiotics and emergency planning.

Increased levels of periodontal pathogens disrupt the homeostasis between the host and its microbiota and increase susceptibility to periodontal diseases. Periodontitis increases the serum concentration of mannose-binding lectin (MBL), which exacerbates local inflammatory processes. In animal studies, sirtuin 1 (SIRT1) was associated with protection against inflammation. This study analyzed the influence of non-surgical periodontal treatment on serum levels of MBL and SIRT1.Forty patients with periodontitis and 38 periodontally healthy individuals (aged 45 to 79 years) were included. Periodontitis patients received scaling and root planing using machine driven and hand instruments. Clinical parameters, inflammatory biomarkers, MBL, and SIRT1 levels were measured at baseline and at post-treatment.For all patients, an inverse correlation was observed between serum concentrations of MBL and SIRT1 (r = -0.30; P = 0.006). Periodontal treatment reduced serum concentrations of MBL (1,099.35 ± 916.59 to 861.42 ± 724.82 ng/mL; P 0.001) and C-reactive protein (6.05 ± 8.99 to 2.49 ± 2.89 mg/L; P = 0.009). By contrast, SIRT1 serum levels increased (1.06 ± 1.03 to 1.66 ± 1.64 ng/mL; P 0.001) following periodontal treatment.Periodontal treatment was associated with decreased serum concentrations of MBL and CRP and increased serum levels of SIRT1. Prospective studies are needed to assess the impact of these biomarkers on pathophysiology of periodontitis.

Objective: Co-deposition of mannose-binding lectin (MBL) and IgG4 anti-phospholipase A2 receptor (anti-PLA2R) autoantibodies under subepithelial cells has been observed in patients with idiopathic membranous nephropathy (iMN), but the relationships of MBL deposition to iMN severity and progression remain unclear. Methods: Patients diagnosed with iMN who underwent renal puncture were enrolled and followed up for a median of 17 months (interquartile range [IQR], 9–25 months). Serum anti-PLA2R and anti-thrombospondin type-1 domain-containing 7A antibodies and MBL were detected by ELISA. Glomerular MBL and anti-PLA2R antibodies were detected by immunofluorescence. Proteinuria remission, including complete remission (CR), was defined as a clinical event. Clinicopathological characteristics and kidney outcomes were compared between patients with and without MBL deposition. Results: In 67 prevalent patients with biopsy-proven iMN, serum anti-PLA2R antibodies and anti-THSD7A antibodies were present in 37 (55.3%) and 1 (1.4%) patient with iMN. The positivity of glomerular MBL deposition and tissue anti-PLA2R antibody was 53 (79.1%) and 49 (73.1%), respectively. No significant difference was found between the MBL-positive and negative groups in the albumin level (26.5 ± 6.6 and 28.6 ± 6.1 g/L), eGFR (104.8 ± 17.4 and 114.6 ± 16.1 mL/min/1.73 m2), 24-h proteinuria (5.35 and 4.25 g/day), or serum MBL level corrected by serum Cr 4.92 (IQR, 0.86, 8.90) and 2.28 (IQR, 0.4, 5.62). In a Cox proportional hazards regression model adjusted for sex, age, systolic blood pressure, eGFR, immunosuppressive agent use, 24-h proteinuria, and anti-PLA2R antibody concentration, glomerular MBL deposition was independently associated with ICR of proteinuria (HR, 6.31; 95% CI, 1.1–36.1; p = 0.039). Conclusions: The MBL pathway of complement activation is commonly initiated in patients with iMN, and patients with MBL deposition reach ICR faster than patients without MBL deposition.

Mannose-binding lectin (MBL) is a soluble pattern-recognition molecule, which plays a crucial role in the innate immune system and the activation of lectin complement pathway. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune disease affecting the small vasculatures and is characterized by the alteration of innate and adaptive immunity and complement activation. In this study, we investigated whether serum MBL is associated with disease activity of AAV, which was measured by ELISA. Associations between serum MBL and AAV-specific indices, as well as clinical and laboratory data were assessed using Kendall's tau. Among the 80 patients, 42 (52.5%), 21 (26.3), and 17 (21.3%) patients were classified as microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA), respectively. The median values of erythrocyte sedimentation rate, C-reactive protein, and serum MBL were 36.5 (normal range < 20) mm/h, 2.4 (normal range < 8) mg/dL, and 8.6 ng/mL, respectively. The median serum levels of MBL in MPA, GPA, and EGPA patients were 8.4, 9.3, and 8.2 ng/mL. Correlation analysis showed that serum MBL was associated with Birmingham Vasculitis Activity Score (BVAS) (R = 0.169, p = 0.027), but not with other AAV-specific indices and clinical and laboratory data. In addition, serum MBL was significantly associated with the pulmonary manifestation score based on BVAS (R = 0.247, p = 0.001). In summary, among the AAV-specific indices and clinical and laboratory variables analyzed, serum MBL is correlated with BVAS and pulmonary manifestation score based on the BVAS.

The mass concentration of specific proteins is often used as a biomarker and play an important part in diagnostics of inflammatory diseases. Monodisperse proteins are robustly measured in immunoassays, but it is considerably more complicated to measure polydisperse oligomeric proteins. The degree of protein oligomerization is critical for functional aspects. For such proteins, information on both the mass concentration as well as the degree of oligomerization is important. Here, a time-resolved immunofluorometric assay (TRIFMA) with sensitivity for protein structure to detect homo-oligomeric and polydisperse proteins is presented. An established TRIFMA for mannan-binding lectin (MBL) was modified by implementing an additional blocking step prior to coating with capture antibodies, leading to a decrease in coating density. Recombinant human MBL was sorted into small, intermediate, and large complexes, using gel permeation chromatography. Small MBL complexes were poorly detectable by TRIFMA with a sparse antibody coating, while larger complexes produced a strong response. From comparison of molecular dimensions, this difference can be related to the size of oligomers. In conclusion, it is possible to design oligomer-size-sensitive immunoassays by regulating the inter-molecular distance of capture antibodies on a scale comparable to the size of the oligomers. The mass concentration of specific proteins is often used as a biomarker and play an important part in diagnostics of inflammatory diseases. Monodisperse proteins are robustly measured in immunoassays, but it is considerably more complicated to measure polydisperse oligomeric proteins. The degree of protein oligomerization is critical for functional aspects. For such proteins, information on both the mass concentration as well as the degree of oligomerization is important. Here, a time-resolved immunofluorometric assay (TRIFMA) with sensitivity for protein structure to detect homo-oligomeric and polydisperse proteins is presented. An established TRIFMA for mannan-binding lectin (MBL) was modified by implementing an additional blocking step prior to coating with capture antibodies, leading to a decrease in coating density. Recombinant human MBL was sorted into small, intermediate, and large complexes, using gel permeation chromatography. Small MBL complexes were poorly detectable by TRIFMA with a sparse antibody coating, while larger complexes produced a strong response. From comparison of molecular dimensions, this difference can be related to the size of oligomers. In conclusion, it is possible to design oligomer-size-sensitive immunoassays by regulating the inter-molecular distance of capture antibodies on a scale comparable to the size of the oligomers.

Alpha-2-macroglobulin is an extracellular macromolecule mainly known for its role as a broad-spectrum protease inhibitor. By presenting itself as an optimal substrate for endopeptidases of all catalytic types, alpha-2-macroglobulin lures active proteases into its molecular cage and subsequently 'flags' their complex for elimination. In addition to its role as a regulator of extracellular proteolysis, alpha-2-macroglobulin also has other functions such as switching proteolysis towards small substrates, facilitating cell migration and the binding of cytokines, growth factors and damaged extracellular proteins. These functions appear particularly important in the context of immune-cell function. In this review manuscript, we provide an overview of all functions of alpha-2-macroglobulin and place these in the context of inflammation, immunity and infections. ispartof: FRONTIERS IN IMMUNOLOGY vol:12 ispartof: location:Switzerland status: published

AimsAlthough the exact factors promoting disease progression in COVID-19 are not fully elucidated, unregulated activation of the complement system (CS) seems to play a crucial role in the pathogenesis of acute lung injury (ALI) induced by SARS-CoV-2. In particular, the lectin pathway (LP) has been implicated in previous autopsy studies. The primary purpose of our study is to investigate the role of the CS in hospitalized COVID-19 patients with varying degrees of disease severity.MethodsIn a single-center prospective observational study, 154 hospitalized patients with PCR-confirmed SARS-CoV-2 infection were included. Serum samples on admission to the COVID-19 ward were collected for analysis of CS pathway activities and concentrations of LP proteins [mannose-binding lectin (MBL) and ficolin-3 (FCN-3)] & C1 esterase inhibitor (C1IHN). The primary outcome was mechanical ventilation or in-hospital death.ResultsThe patients were predominately male and had multiple comorbidities. ICU admission was required in 16% of the patients and death (3%) or mechanical ventilation occurred in 23 patients (15%). There was no significant difference in LP activity, MBL and FCN-3 concentrations according to different peak disease severities. The median alternative pathway (AP) activity was significantly lower (65%, IQR 50-94) in patients with death/invasive ventilation compared to patients without (87%, IQR 68-102, p=0.026). An optimal threshold of ConclusionOur results point to an overactivated AP in critically ill COVID-19 patients in vivo leading to complement consumption and consequently to a significantly reduced AP activity in vitro. The LP does not seem to play a role in the progression to severe COVID-19. Apart from its acute phase reaction the significance of C1INH in COVID-19 requires further studies.

Mannose-binding lectin-associated serine protease-1 (MASP-1) is known to interact with complement and coagulation pathways. Recently it was reported that MASP-1 interacts with the fibrinolytic system but details remain unclear. The objective of the study is to find MASP-1 substrates that participate in the fibrinolytic system. Commercially available fibrinogen might contain some impurities. Fibrinogen was treated with MASP-1 followed by analysis on SDS-PAGE and the obtained cleaved fragments were identified by matrix-assisted laser desorption/ionization-time of flight/time of flight. Functional analysis of identified substrate was confirmed by fluorogenic and turbidimetric assay. Statistical analysis was done by using the Student t test. This study reports that plasminogen and plasma fibronectin are two hitherto unknown substrates of MASP-1. Conversion of plasminogen to plasmin like molecule by MASP-1 was confirmed by cleavage of plasmin specific substrate and digestion of fibrin clot. The role of MASP-1 in clot dissolution was confirmed by turbidity assay. Our study shows that MASP-1 selects plasminogen over fibrinogen to be a preferable substrate. MASP-1 promotes the fibrinolytic activity by the generation of plasmin like molecule from plasminogen and further destabilizes the clot by digestion of plasma fibronectin.

BackgroundThe SARS-CoV-2 infection triggers excessive immune response resulting in increased levels of pro-inflammatory cytokines, endothelial injury, and intravascular coagulopathy. The complement system (CS) activation participates to this hyperinflammatory response. However, it is still unclear which activation pathways (classical, alternative, or lectin pathway) pilots the effector mechanisms that contribute to critical illness. To better understand the immune correlates of disease severity, we performed an analysis of CS activation pathways and components in samples collected from COVID-19 patients hospitalized in Grenoble Alpes University Hospital between 1 and 30 April 2020 and of their relationship with the clinical outcomes.MethodsWe conducted a retrospective, single-center study cohort in 74 hospitalized patients with RT-PCR-proven COVID-19. The functional activities of classical, alternative, and mannose-binding lectin (MBL) pathways and the antigenic levels of the individual components C1q, C4, C3, C5, Factor B, and MBL were measured in patients’ samples during hospital admission. Hierarchical clustering with the Ward method was performed in order to identify clusters of patients with similar characteristics of complement markers. Age was included in the model. Then, the clusters were compared with the patient clinical features: rate of intensive care unit (ICU) admission, corticoid treatment, oxygen requirement, and mortality.ResultsFour clusters were identified according to complement parameters. Among them, two clusters revealed remarkable profiles: in one cluster (n = 15), patients exhibited activation of alternative and lectin pathways and low antigenic levels of MBL, C4, C3, Factor B, and C5 compared to all the other clusters; this cluster had the higher proportion of patients who died (27%) and required oxygen support (80%) or ICU care (53%). In contrast, the second cluster (n = 19) presented inflammatory profile with high classical pathway activity and antigenic levels of complement components; a low proportion of patients required ICU care (26%) and no patient died in this group.ConclusionThese findings argue in favor of prominent activation of the alternative and MBL complement pathways in severe COVID-19, but the spectrum of complement involvement seems to be heterogeneous requiring larger studies.

Background Coronary artery disease (CAD) develops as a result of atherosclerosis. Atherosclerosis is a condition that leads to clogged arteries and can be caused by a variety of factors. Several studies have shown that various factors contribute to the development and progression of CAD. The aim of this study was to investigate the serum levels of MBL‐2, TNC and TAC in patients with CAD and the relationship between these biochemical parameters and the progression of CAD. Methods In this study, 60 serum samples were obtained from CAD patients as the case group and 20 healthy serum samples as the control group. Serum levels of MBL‐2 and TNC were measured by the ELISA method. Serum TAC level was determined by calorimetry (spectrophotometry). In addition, MDA serum level was measured by reaction with thiobarbituric acid (TBA). Results The mean age in the case and control groups was 58.4 ± 9.5 years and 85 ± 9.8 years, respectively. There was no significant difference in age, sex and family history in patients with CAD (p > 0.05), but there was a significant difference in blood pressure and smoking history (p > 0.05). Serum cholesterol, triglyceride, and LDL levels were significantly increased in the case group compared to the control group, while serum HDL‐C levels were significantly decreased in the case group. Serum levels of MBL‐2, TNC, and MDA were significantly increased in the case group compared to the control group. The serum level of TAC was significantly lower in the case group than in the control group. Conclusion This study suggests that it is possible to diagnose patients with coronary artery disease (CAD) in the early stages of their disease and take preventive measures by measuring these parameters in serum. However, more research is needed before these serum parameters can be considered diagnostic biomarkers or therapeutic targets., Background: Coronary Artery Disease (CAD) develops as a result of atherosclerosis. Atherosclerosis is a condition that leads to clogged arteries and can be caused by a variety of factors. The aim of this study is to investigate the serum levels of MBL‐2, TNC and TAC in patients with CAD and the relationship between these biochemical parameters and the progression of CAD. Methods: In this study, 60 serum samples were obtained from CAD patients as the case group and 20 healthy serum samples as the control group. Serum levels of MBL‐2 and TNC were measured by the ELISA method. Serum TAC level was determined by calorimetry (spectrophotometry). In addition, MDA serum level was measured by reaction with thiobarbituric acid (TBA). Results: The mean age in the case and control groups was 58.4 ± 9.5 years and 85 ± 9.8 years, respectively. There was no significant difference in age, sex and family history in CAD patients (p > 0.05), but there was a significant difference in blood pressure and smoking history (p > 0.05). Serum levels of MBL‐2, TNC and MDA, were significantly increased in the case group compared to the control group. The serum level of TAC was significantly lower in the case group than in the control group. Conclusion: This study suggests that it is possible to diagnose patients with coronary artery disease (CAD) in the early stages of their disease and take preventive measures by measuring these parameters in serum. However, more research is needed before these serum parameters can be considered diagnostic biomarkers.

The rapid outbreak of COVID-19 caused by the novel coronavirus SARS-CoV-2 in Wuhan, China, has become a worldwide pandemic affecting almost 204 million people and causing more than 4.3 million deaths as of August 11 2021. This pandemic has placed a substantial burden on the global healthcare system and the global economy. Availability of novel prophylactic and therapeutic approaches are crucially needed to prevent development of severe disease leading to major complications both acutely and chronically. The success in fighting this virus results from three main achievements: (a) Direct killing of the SARS-CoV-2 virus; (b) Development of a specific vaccine, and (c) Enhancement of the host’s immune system. A fundamental necessity to win the battle against the virus involves a better understanding of the host’s innate and adaptive immune response to the virus. Although the role of the adaptive immune response is directly involved in the generation of a vaccine, the role of innate immunity on RNA viruses in general, and coronaviruses in particular, is mostly unknown. In this review, we will consider the structure of RNA viruses, mainly coronaviruses, and their capacity to affect the lungs and the cardiovascular system. We will also consider the effects of thepattern recognition protein (PRP) tridentcomposed by (a) Surfactant proteins A and D, mannose-binding lectin (MBL) and complement component 1q (C1q), (b) C-reactive protein, and (c) Innate and adaptive IgM antibodies, upon clearance of viral particles and apoptotic cells in lungs and atherosclerotic lesions. We emphasize on the role of pattern recognition protein immune therapies as a combination treatment to prevent development of severe respiratory syndrome and to reduce pulmonary and cardiovascular complications in patients with SARS-CoV-2 and summarize the need of a combined therapeutic approach that takes into account all aspects of immunity against SARS-CoV-2 virus and COVID-19 disease to allow mankind to beat this pandemic killer.

Titanium and its alloys are used biomaterials for medical and dental applications, due to their mechanical and physical properties. The surface modifications of titanium with bioactive molecules can increase the osseointegration by improving the interface between the bone and implant. Titanium dioxide nanotubes (TiO2NTs) have excellent bioactivity inducing cell adhesion, spreading, growth and differentiation. In this work, TiO2NTs were functionalized with a lectin from the plasma of the fish Oreochromis niloticus aiming to favour the adhesion and proliferation of osteoblast-like cells, improving its biocompatibility. The TiO2NTs were obtained by anodization of titanium and annealed at 400 °C for 3 h. The resulting TiO2NTs were characterized by high-resolution scanning electron microscopy. The successfully incorporation of OniL on the surface of TiO2NTs by spin coating was demonstrated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIE) and attenuated total reflection-Fourier transform infrared spectrum (ATR-FTIR). Our results showed that TiO2-NTs were successfully synthesized in a regular and well-distributed way. The functionalization of TiO2-NTs with OniL favoured adhesion, proliferation, and the osteogenic activity of osteoblast-like cells, suggesting its use to improve the quality and biocompatibility of titanium-based biomaterials.

BackgroundThe innate and adaptive immune system is involved in the airway inflammation associated with acute exacerbations in patients with chronic obstructive pulmonary disease (COPD). We evaluated the association of mannose-binding lectin (MBL), immunoglobulin (Ig) and ficolin-2 concentrations with COPD exacerbations and according to the glucocorticoid treatment duration for an index exacerbation.MethodsPost-hoc analysis of the randomized, double-blind, placebo-controlled REDUCE trial of 5 vs. 14 days of glucocorticoid treatment for an index exacerbation. MBL, ficolin-2 and total IgG/IgA and subclass concentrations were determined in stored samples drawn (n = 178) 30 days after the index exacerbation and associated with the risk of re-exacerbation during a 180-day follow-up period.ResultsIgG and subclass concentrations were significantly lower after 14 days vs. 5 days of glucocorticoid treatment. Patients with higher MBL concentrations were more likely to suffer from a future exacerbation (multivariable hazard ratio 1.03 per 200 ng/ml increase (95% confidence interval (CI) 1.00–1.06), p = 0.048), whereas ficolin-2 and IgG deficiency were not associated. The risk was most pronounced in patients with high MBL concentrations, IgG deficiency and 14 days of glucocorticoid treatment pointing towards an interactive effect of MBL and IgG deficiency in the presence of prolonged glucocorticoid treatment duration [Relative excess risk due to interaction 2.13 (95% CI − 0.41–4.66, p = 0.10)]. IgG concentrations were significantly lower in patients with frequent re-exacerbations (IgG, 7.81 g/L vs. 9.53 g/L, p = 0.03).ConclusionsMBL modified the short-term exacerbation risk after a recent acute exacerbation of COPD, particularly in the setting of concurrent IgG deficiency and recent prolonged systemic glucocorticoid treatment. Ficolin-2 did not emerge as a predictor of a future exacerbation risk.

The aberrant release of endoplasmic reticulum (ER) calcium leads to the disruption of intracellular calcium homeostasis, which is associated with the occurrence of ER stress and closely related to the pathogenesis of liver damage. Mannan-binding lectin (MBL) is a soluble calcium-dependent protein synthesized primarily in hepatocytes and is a pattern recognition molecule in the innate immune system. MBL deficiency is highly prevalent in the population and has been reported to be associated with susceptibility to several liver diseases. We here showed that genetic MBL ablation strongly sensitized mice to ER stress-induced liver injury. Mechanistic studies established that MBL directly interacted with ER-resident chaperone immunoglobulin heavy chain binding protein (BiP), and MBL deficiency accelerated the separation of PKR-like ER kinase (PERK) from BiP during hepatic ER stress. Moreover, MBL deficiency led to enhanced activation of the PERK-C/EBP-homologous protein (CHOP) pathway and initiates an inositol 1,4,5-trisphosphate receptor (IP3R)-mediated calcium release from the ER, thereby aggravating the hepatic ER stress response. Our results demonstrate an unexpected function of MBL in ER calcium homeostasis and ER stress response, thus providing new insight into the liver injury related to ER stress in patients with MBL deficiency.

SummaryThe humoral arm of innate immunity includes diverse molecules with antibody-like functions, some of which serve as disease severity biomarkers in COVID-19. The present study was designed to conduct a systematic investigation of the interaction of humoral fluid phase pattern recognition molecules (PRM) with SARS-CoV-2. Out of 10 PRM tested, the long pentraxin PTX3 and Mannose Binding Lectin (MBL) bound the viral Nucleoprotein and Spike, respectively. MBL bound trimeric Spike, including that of variants of concern, in a glycan- dependent way and inhibited SARS-CoV-2 in threein vitromodels. Moreover, upon binding to Spike, MBL activated the lectin pathway of complement activation. Genetic polymorphisms at the MBL locus were associated with disease severity. These results suggest that selected humoral fluid phase PRM can play an important role in resistance to, and pathogenesis of, COVID-19, a finding with translational implications.

Prognostic characteristics inform risk stratification in intensive care unit (ICU) patients with coronavirus disease 2019 (COVID-19). We obtained blood samples (n = 474) from hospitalized COVID-19 patients (n = 123), non-COVID-19 ICU sepsis patients (n = 25) and healthy controls (n = 30). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA was detected in plasma or serum (RNAemia) of COVID-19 ICU patients when neutralizing antibody response was low. RNAemia is associated with higher 28-day ICU mortality (hazard ratio [HR], 1.84 [95% CI, 1.22–2.77] adjusted for age and sex). RNAemia is comparable in performance to the best protein predictors. Mannose binding lectin 2 and pentraxin-3 (PTX3), two activators of the complement pathway of the innate immune system, are positively associated with mortality. Machine learning identified ‘Age, RNAemia’ and ‘Age, PTX3’ as the best binary signatures associated with 28-day ICU mortality. In longitudinal comparisons, COVID-19 ICU patients have a distinct proteomic trajectory associated with mortality, with recovery of many liver-derived proteins indicating survival. Finally, proteins of the complement system and galectin-3-binding protein (LGALS3BP) are identified as interaction partners of SARS-CoV-2 spike glycoprotein. LGALS3BP overexpression inhibits spike-pseudoparticle uptake and spike-induced cell-cell fusion in vitro., Here the authors use RT-qPCR and mass spectrometry to analyze longitudinal blood samples from intensive care unit (ICU) COVID-19 patients and controls. They find that viral RNA and pentraxin-3 predict 28-day ICU mortality and that galectin-3-binding protein is an interaction partner of SARS-CoV-2 spike glycoprotein with antiviral properties.

Introduction The SARS-CoV-2 virus has infected more than 63,000,000 people worldwide after emerging from Wuhan, China in December 2019. This outbreak was declared a Public Health Emergency in January 2020, and a pandemic in March. While rare, reinfection with the virus has been reported on multiple occasions. Case Presentation We present a case report of an individual with mannose binding lectin deficiency who tested positive on two separate occasions, months apart, and did not develop IgG antibodies to SARS-CoV-2. This patient Is a 30- year-old female healthcare worker with a past medical history of ITP, pancreatitis, GERD, anxiety and recurrent pneumonia. She presented in March 2020 with fever, nasal congestion, and dry cough. She was diagnosed with COVID-19 in March 2020, via PCR through employee health. She was treated with a course azithromycin and hydroxychloroquine. Symptoms resolved, however in June 2020, SARS-CoV-2 IgG antibodies were negative. Seven months later in October, she once again developed symptoms which were milder. She was found to have a decreased level of mannose binding lectin, normal immunoglobulin levels, and normal streptococcus pneumonia IgG antibodies. On immune work-up after recovery, she was found to have a decreased level of mannose binding lectin (Discussion This case illustrates that patients with mannose binding lectin deficiency may be at greater risk of re-infection than the general population.

Dengue is a mosquito-borne viral disease causing significant health and economic burdens globally. The dengue virus (DENV) comprises four serotypes (DENV1-4). Usually, the primary infection is asymptomatic or causes mild dengue fever (DF), while secondary infections with a different serotype increase the risk of severe dengue disease (dengue hemorrhagic fever, DHF). Complement system activation induces inflammation and tissue injury, contributing to disease pathogenesis. However, in asymptomatic or primary infections, protective immunity largely results from the complement system’s lectin pathway (LP), which is activated through foreign glycan recognition. Differences in N-glycans displayed on the DENV envelope membrane influence the lectin pattern recognition receptor (PRR) binding efficiency. The important PRR, mannan binding lectin (MBL), mediates DENV neutralization through (1) a complement activation-independent mechanism via direct MBL glycan recognition, thereby inhibiting DENV attachment to host target cells, or (2) a complement activation-dependent mechanism following the attachment of complement opsonins C3b and C4b to virion surfaces. The serum concentrations of lectin PRRs and their polymorphisms influence these LP activities. Conversely, to escape the LP attack and enhance the infectivity, DENV utilizes the secreted form of nonstructural protein 1 (sNS1) to counteract the MBL effects, thereby increasing viral survival and dissemination.

Agaricus bisporus mannose binding protein (Abmb) demonstrates permeability to epithelial monolayer barrier of the intestine, resistance to gastrointestinal tract conditions and to proteolysis therefore it holds potential as a drug carrier for oral route administration. Abmb also display antiproliferative activity to breast cancer cells and stimulation of immune system thus could potentially be also developed for therapeutic purpose. It is not immunogenic or toxic thereby safe for use. In this paper we further provide evidence that Abmb also lacks of agglutinating activity despite sharing high structural homology to lectins. Abmb is thereby the only mannose specific binding protein that is not member of lectin family. This evidence provides further support on the use of Abmb as pharmaceutical or medicinal agent. Its molecular globularity that may contribute to its lack of agglutination capacity was also evaluated.

Bacterial dysbiosis accompanies carcinogenesis in malignancies such as colon and liver cancer, and has recently been implicated in the pathogenesis of pancreatic ductal adenocarcinoma (PDA)1. However, the mycobiome has not been clearly implicated in tumorigenesis. Here we show that fungi migrate from the gut lumen to the pancreas, and that this is implicated in the pathogenesis of PDA. PDA tumours in humans and mouse models of this cancer displayed an increase in fungi of about 3,000-fold compared to normal pancreatic tissue. The composition of the mycobiome of PDA tumours was distinct from that of the gut or normal pancreas on the basis of alpha- and beta-diversity indices. Specifically, the fungal community that infiltrated PDA tumours was markedly enriched for Malassezia spp. in both mice and humans. Ablation of the mycobiome was protective against tumour growth in slowly progressive and invasive models of PDA, and repopulation with a Malassezia species—but not species in the genera Candida, Saccharomyces or Aspergillus—accelerated oncogenesis. We also discovered that ligation of mannose-binding lectin (MBL), which binds to glycans of the fungal wall to activate the complement cascade, was required for oncogenic progression, whereas deletion of MBL or C3 in the extratumoral compartment—or knockdown of C3aR in tumour cells—were both protective against tumour growth. In addition, reprogramming of the mycobiome did not alter the progression of PDA in Mbl- (also known as Mbl2) or C3-deficient mice. Collectively, our work shows that pathogenic fungi promote PDA by driving the complement cascade through the activation of MBL. In humans and mouse models, the mycobiome of pancreatic ductal adenocarcinoma tumours is markedly enriched in Malassezia species compared to that of normal pancreas, which implicates these pathogenic fungi in oncogenesis.

Background Cryptococcal meningitis is most commonly found in HIV-infected patients. In HIV-negative patients, its low incidence can lead to prolonged time to diagnosis. Detailed case reports of chronic cryptococcal meningitis are scarce, but could provide clues for earlier diagnosis in this patient category. Case presentation A 60-year old man presented June 2015 with intermittent headaches for several months without any fever. Initial work-up showed a leukocytosis, raised CSF opening pressure and raised leukocytes and protein in the CSF. An MRI revealed leptomeningeal contrast enhancement and cerebellar oedema. While malignancy and various infectious causes were excluded, the patient had a spontaneous clinical and radiological recovery. One year later, the patient returned with complaints of headaches. Also, cerebellar oedema and leptomeningeal contrast enhancement had recurred. Eventually in March 2017, the novel cryptococcal antigen lateral flow assay (CrAg LFA) was positive on CSF, and one colony of Cryptococcus neoformans was cultured from CSF. The patient was treated with the standard antifungal regimen which resulted in resolution of his headaches. In retrospect, the cryptococcal antigen test was already positive on a serum sample from June 2015. Interestingly, post-treatment immunological analysis revealed both a low mannose-binding lectin (MBL) concentration and low naïve CD4 counts. Conclusions We present a patient with cryptococcal meningitis in an HIV-negative patient with low MBL and low naïve CD4 count suffering a chronic relapsing meningo-encephalitis with relatively mild symptoms for around 2 years. In patients with an unexplained meningo-encephalitis such as this case, early performance of CrAg LFA on serum and/or CSF is an inexpensive and rapid method to reduce time-to diagnosis.

Background To determine the serum levels of the lectin pathway proteins early in the disease course and 17 years after disease onset and to correlate the protein levels to markers of disease activity in participants from a population-based Nordic juvenile idiopathic arthritis (JIA) cohort. Additionally, to assess the predictive value of lectin pathway proteins with respect to remission status. Methods A population-based cohort study of consecutive cases of JIA with a disease onset from 1997 to 2000 from defined geographical areas of Finland, Sweden, Norway and Denmark with 17 years of follow-up was performed. Clinical characteristics were registered and H-ficolin, M-ficolin, MASP-1, MASP-3, MBL and CL-K1 levels in serum were analyzed. Results In total, 293 patients with JIA were included (mean age 23.7 ± 4.4 years; mean follow-up 17.2 ± 1.7 years). Concentrations of the lectin protein levels in serum were higher at baseline compared to the levels 17 years after disease onset (p ≤ 0.006, n = 164). At baseline, the highest level of M-ficolin was observed in systemic JIA. Further, high M-ficolin levels at baseline and at 17-year follow-up were correlated to high levels of ESR. In contrast, high MASP-1 and MASP-3 tended to correlate to low ESR. CL-K1 showed a negative correlation to JADAS71 at baseline. None of the protein levels had prognostic abilities for remission status 17 years after disease onset. Conclusion We hypothesize that increased serum M-ficolin levels are associated with higher disease activity in JIA and further, the results indicate that MASP-1, MASP-3 and CL-K1 are markers of inflammation.

Mannose-binding lectin (MBL), an initiator of the lectin pathway, is detrimental in ischemic stroke. MBL deposition on the ischemic endothelium indicates the beginning of its actions, but downstream mechanisms are not clear yet. We investigated MBL interactions with the ischemic endothelium by exposing human brain microvascular endothelial cells (hBMECs) to protocols of ischemia. Cells were exposed to hypoxia or oxygen–glucose deprivation (OGD), and re-oxygenated with human serum (HS) or recombinant MBL (rhMBL). Hypoxic hBMECs re-oxygenated with HS showed increased complement system activation (C3c deposition, +59%) and MBL deposition (+93%) than normoxic cells. Super-resolution microscopy showed MBL internalization in hypoxic cells and altered cytoskeletal organization, indicating a potential MBL action on the endothelial structure. To isolate MBL effect, hBMECs were re-oxygenated with rhMBL after hypoxia/OGD. In both conditions, MBL reduced viability (hypoxia: −25%, OGD: −34%) compared to conditions without MBL, showing a direct toxic effect. Ischemic cells also showed greater MBL deposition (hypoxia: +143%, OGD: +126%) than normoxic cells. These results were confirmed with primary hBMECs exposed to OGD (increased MBL-induced cell death: +226%, and MBL deposition: +104%). The present findings demonstrate that MBL can exert a direct deleterious effect on ischemic brain endothelial cells in vitro, independently from complement activation.

Introduction: This study aimed to determine the association between serum mannose-binding lectin (MBL) levels, gene polymorphisms and late-onset sepsis (LOS) in preterm infants. Methods: Infants with

Mannose-binding lectin-associated serine protease-1 (MASP-1), a multifunctional serine protease, plays an important role in innate immunity which is capable of activating the lectin pathway of the complement system and also triggering coagulation cascade system. In this study, a MASP-1 homolog (OnMASP-1) was identified from Nile tilapia (Oreochromis niloticus) and characterized at expression and inflammation functional levels. The open reading frame (ORF) of OnMASP-1 is 2187 bp of nucleotide sequence encoding a polypeptide of 728 amino acids. The deduced amino acid sequence has 6 characteristic structures, including two C1r/C1s-Uegf-BMP domains (CUB), one epidermal growth factor domain (EGF), two complement control protein domains (CCP) and a catalytic serine protease domain (SP). Expression analysis revealed that the OnMASP-1 was highly expressed in the liver, and widely exhibited in other tissues containing intestine, spleen and kidney. In addition, the OnMASP-1 expression was significantly up-regulated in spleen and head kidney following challenges with Streptococcus agalactiae and Aeromonas hydrophila. The up-regulations of OnMASP-1 mRNA and protein expression were also demonstrated in hepatocytes and monocytes/macrophages in vitro stimulation with S. agalactiae and A. hydrophila. Recombinant OnMASP-1 protein was likely to participate in the regulation of inflammatory and migration reaction by monocytes/macrophages. These results indicated that OnMASP-1, playing an important role in innate immunity, was likely to involve in host defense against bacterial infection in Nile tilapia.

Factors influencing fallopian tube occlusion in women with a lower genital tract infection remain incompletely elucidated. We evaluated whether a polymorphism in the mannose-binding lectin (MBL) gene at codon 54 influences the occurrence of fallopian tube blockage in relation to exposure to Chlamydia trachomatis. In a case–control study at The Hospital das Clinicas, University of Sao Paulo, Brazil, 75 women with hysterosalpingography-documented tubal occlusion and 75 women with patent fallopian tubes were analyzed for detection of single-nucleotide polymorphism in codon 54 of the MBL gene and for IgG anti-C. trachomatis antibodies in their sera. Both groups were matched for age, race, and sexual variables. Prior exposure to C. trachomatis, as evidenced by the presence of IgG antibodies, was comparable in both groups. Detection of the polymorphic MBL allele was more prevalent in women with blocked tubes (p

Summary Despite improvements in treatment, coronary artery disease is still responsible for one-third of all deaths globally, due predominantly to myocardial infarction (MI) and stroke. There is an important potential in developing new strategies for treatment of patients with these conditions. Inflammation, and in particular the actions of the complement system, has emerged as part of the pathogenesis in reperfusion injury in patients with MI. To further qualify this, we examined the association between the plasma levels of lectin pathway proteins and myocardial end-points, left ventricular ejection fraction (LVEF) and infarct size in a cohort of patients with ST-elevation myocardial infarction (STEMI). A blood sample was drawn the day after percutaneous coronary intervention from 73 patients with STEMI. The primary end-points, LVEF and infarct size, were measured with magnetic resonance imaging 6–9 days after the infarct. Complement pattern-recognition molecules of the lectin pathway (mannan-binding lectin, H-ficolin, L-ficolin and M-ficolin) were analysed along with soluble membrane attack complex (sMAC) and C-reactive protein (CRP) in plasma with immunofluorometric assays

The aim of this immunocytochemical study was to compare mannose-binding lectin (MBL) production induced by avian coronavirus in the spleen and caecal tonsil (CT). One-day-old specific-pathogen-free (SPF) chickens were experimentally infected with six QX field isolates and the H120 vaccine strain. In the negative control birds, the spleen was MBL negative, while the CT showed scattered MBL-positive cells in close proximity and within the surface epithelium and germinal centre (GC)-like cell clusters. MBL was detectable in the ellipsoid-associated cells (EACs) and cell clusters in the periarterial lymphoid sheath (PALS) by 7 days post infection (dpi). In both organs, the MBL-positive cells occupy antigen-exposed areas, indicating that GC formation depends on resident precursors of dendritic cells. The majority of MBL-positive EACs express the CD83 antigen, providing evidence that coronavirus infection facilitated the maturation of dendritic cell precursors. Surprisingly, co-localisation of MBL and CD83 was not detectable in the CT. In the spleen (associated with circulation), the EACs producing MBL and expressing CD83 are a common precursor of both follicular (FDC) and interdigitating dendritic cells (IDC). In the CT (gut-associated lymphoid tissue, GALT) the precursors of FDC and IDC are MBL-producing cells and CD83-positive cells, respectively. In the CT the two separate precursors of lymphoid dendritic cells provide some ‘autonomy’ for the GALT.

Mannose binding lectin 2 (MBL2) is one of the pattern-recognition soluble receptors and is responsible for complement activation via the lectin pathway, so it plays an important role in kidney transplantation. The aim of the study was to examine the association between MBL2 gene polymorphisms and acute rejection of the kidney allograft. This study enrolled 266 Caucasian deceased-donor renal transplant recipients - 69 with diagnosed acute graft rejection, 197 with stable graft function. A 969 bp DNA fragment, from chromosome 10, including promoter region and exon 1 of MBL2 gene was sequenced. The DNA fragment obtained contained 122 SNPs accordingly to the NCBI dbSNP database. Of this number only nine showed variation within our population (rs36014597, rs5030737, rs1800450, rs7095891, rs11003123, rs7096206, rs7084554, rs11003124, rs11003125), and only these were subjected to further analysis. Among the studied polymorphisms in the MBL2 gene only rs1800450 polymorphism was statistically significantly associated with kidney allograft rejection. The AA genotype was significantly associated with an increased risk of acute kidney allograft rejection. (AA vs GA+GG: OR=9.29 (95%CI: 1.83-47.17), p=0.005). The results of our study indicate that MBL2 gene rs1800450 polymorphism may be associated with the risk of acute kidney allograft rejection. The AA genotype, associated with lower MBL2 expression, may be associated with an increased risk of acute kidney allograft rejection.

Background Mannose-binding lectin (MBL) deficiency may increase risk of respiratory tract infection in adults unselected for IgG or IgG subclass levels. In a retrospective study, we sought to determine associations of serum MBL levels with clinical and laboratory characteristics of unrelated non-Hispanic white adults at diagnosis of IgG subclass deficiency (IgGSD). We computed the correlation of first and second MBL levels expressed as natural logarithms (ln) in a patient subgroup. We compared these characteristics of all adults with and without MBL ≤50 ng/mL: age; sex; body mass index; upper/lower respiratory tract infection; diabetes; autoimmune condition(s); atopy; other allergy; corticosteroid therapy; and subnormal serum IgG subclasses, IgA, and IgM. We performed logistic regression on MBL ≤50 ng/mL (dichotomous) using the three independent variables with the lowest values of p in univariate comparisons. Results There were 219 patients (mean age 51 ± 13 y; 82.5% women). Thirty-six patients (16.4%) had MBL ≤50 ng/mL. Two MBL measurements were available in 14 patients. The median interval between the first and second measurements was 125 d (range 18–1031). For ln-transformed data, we observed adjusted r2 = 0.9675; Pearson correlation coefficient 0.9849; and p

ObjectivesTo evaluate renal expression of C4d, a complement component in the classical/mannose binding lectin (MBL) pathway, in patients with primary Sjögren’s syndrome (pSS)-associated renal impairments.MethodsWe retrospectively reviewed the clinical and pathological data from 39 patients with pSS presenting with renal impairments. C4d was examined in paraffin-embedded biopsy tissues using immunohistochemistry. Glomerular C4d positive was defined when >75% glomeruli were globally stained. Tubulointerstitial C4d (TI-C4d) were scored semi-quantitatively as 0 (absent), 1 (spotty or weak), 2 (patchy) and 3 (diffuse). A TI-C4d score ≥2 was considered TI-C4d positive and included in the TI-C4d+ group and vice versa. Peritubular capillary (PTC) C4d was scored as 0 (absent), 1 (0∼10%, minimal), 2 (10%∼50%, focal), and 3 (>50%, diffuse).ResultsGlomerular C4d deposition was observed in all 8 patients with pSS-related membranous nephropathy (MN) without obvious C1q deposition. Two of 5 patients with mesangial proliferative glomerulonephritis and 1 of 2 patients with IgA nephropathy had mild mesangial C4d deposition. Sixteen patients (6 glomerular dominant and 10 tubulointerstitial dominant) presented TI-C4d score ≥2. Patients in the TI-C4d+ group exhibited a higher serum creatinine level at the time of renal biopsy (TI-C4d+ 132.5 [89.7, 165.5] vs. TI-C4d- 83.0 [70.7, 102.0] μmol/L, P=0.008). PTC C4d was observed in 12 patients, with each of minimal, focal and diffuse staining being noted in 4 patients.ConclusionsThe MBL pathway of complement activation was potentially involved in pSS-related MN. Tubulointerstitial C4d might be a pathological marker of severe renal injury in patients with pSS-related renal impairments.

Background Activation of the complement system is part of the dysregulated immune response in sepsis. The mannose-binding lectin-associated serine proteases (MASP)-1 and -2 activate the lectin pathway of the complement system. Besides, these proteins can activate coagulation in vitro. However, the role of the lectin pathway proteins in the development of sepsis-related disseminated intravascular coagulation (DIC) is only sparsely investigated. Aim This article investigates the association between lectin pathway proteins and coagulation disturbances in septic shock patients. Materials and Methods We included 36 septic shock patients from the intensive care unit, Aarhus University Hospital, Denmark. Blood samples were obtained within 24 hours after admission (day 1), and subsequently on day 2 and day 3. Plasma concentrations of mannose-binding lectin (MBL), H-ficolin, M-ficolin, CL-L1, CL-K1, MASP-1, -2 and -3, MBL-associated proteins of 19 and 44 kDa as well as complement factor C3dg were assessed. Standard coagulation parameters, thrombin generation, thrombin–anti-thrombin (TAT) complex and pro-thrombin fragment 1 + 2 were measured. Sequential Organ Failure Assessment (SOFA) score, DIC score and 30-day mortality were assessed. Results Reduced MASP-1 plasma concentration was associated with DIC score ≥5 (p = 0.02), impaired thrombin generation (p = 0.03) and lower plasma TAT complex levels (p = 0.03). No association was found between lectin pathway proteins and SOFA score or 30-day mortality. Conclusion Reduced MASP-1 concentrations were associated with impaired coagulation in septic shock patients. This indicates that increased MASP-1 activation and consumption is associated with the more severe coagulation disturbances in sepsis and points to a possible role for MASP-1 in sepsis-related DIC.