Mannan-binding lectin (MBL) gene polymorphisms in ulcerative colitis and Crohn's disease

Association of mannose binding lectin with chronic obstructive pulmonary disease susceptibility and its clinical outcomes

BACKGROUND

The physiological interactions of MBL suggest its contribution towards the pathogenesis of COPD.

OBJECTIVE

The present case-control study was undertaken to elucidate the role of MBL with COPD risk and clinical outcomes in north Indian cohort.

METHODS

Patients were enrolled as per GOLD criteria. MBL2 variants were selected based on the literature and their putative functional significance. Genotyping of six single nucleotide polymorphisms of MBL2 comprising of two coding (rs1800450, rs1800451) and four non-coding variants (rs11003125, rs7096206, rs11003123 and rs7095891) was done by using PCR-RFLP and ARMS-PCR. Serum MBL levels were analysed by sandwich ELISA.

RESULTS

Overall findings of the molecular genetic analysis of MBL2 indicated significant difference in frequency of three of the six studied variants, between patients and controls or among different disease severity stages. Heterozygous genotype of rs7095891 showed significant protective association towards severity of disease. Linkage disequilibrium (LD) analysis indicated a strong LD between rs1800450 and rs7095891 while intermediate LD was observed for rs11003123/rs11003125 and rs7096206/rs11003125. Haplotype analysis revealed 17.14-fold risk of developing exacerbations conferred by GGGTGG haplotype. Significantly low serum MBL levels observed in COPD patients as compared to controls. Significant difference in MBL deficiency levels were also observed for homozygous wild and variant genotypes of rs11003125 and rs7096206 respectively, as well as for all genotypes of rs11003123 than respective controls.

CONCLUSION

The present study reinforces the role played by MBL in the susceptibility, protection and clinical outcomes of COPD. Therefore, including the reported associations at diagnostic, prognostic and therapeutic interventions may prove helpful.

Serum TGF-β1 and CD14 Predicts Response to Anti-TNF-α Therapy in IBD

Background

Tumor necrosis factor-alpha (TNF-α) agonists revolutionized therapeutic algorithms in inflammatory bowel disease (IBD) management. However, approximately every third IBD patient does not respond to this therapy in the long term, which delays efficient control of the intestinal inflammation.

Methods

We analyzed the power of serum biomarkers to predict the failure of anti-TNF-α. We collected serum of 38 IBD patients at therapy prescription and 38 weeks later and analyzed them with relation to therapy response (no-, partial-, and full response). We used enzyme-linked immunosorbent assay to quantify 16 biomarkers related to gut barrier (intestinal fatty acid-binding protein, liver fatty acid-binding protein, trefoil factor 3, and interleukin (IL)-33), microbial translocation, immune system regulation (TNF-α, CD14, lipopolysaccharide-binding protein, mannan-binding lectin, IL-18, transforming growth factor-β1 (TGF-β1), osteoprotegerin (OPG), insulin-like growth factor 2 (IGF-2), endocrine-gland-derived vascular endothelial growth factor), and matrix metalloproteinase system (MMP-9, MMP-14, and tissue inhibitors of metalloproteinase-1).

Results

We found that future full-responders have different biomarker profiles than non-responders, while partial-responders cannot be distinguished from either group. When future non-responders were compared to responders, their baseline contained significantly more TGF-β1, less CD14, and increased level of MMP-9, and concentration of these factors could predict non-responders with high accuracy (AUC = 0.938). Interestingly, during the 38 weeks, levels of MMP-9 decreased in all patients, irrespective of the outcome, while OPG, IGF-2, and TGF-β1 were higher in non-responders compared to full-responders both at the beginning and the end of the treatment.

Conclusions

The TGF-β1 and CD14 can distinguish non-responders from responders. The changes in biomarker dynamics during the therapy suggest that growth factors (such as OPG, IGF-2, and TGF-β) are not markedly influenced by the treatment and that anti-TNF-α therapy decreases MMP-9 without influencing the treatment outcome.

Investigation of MBL2 and NOS3 functional gene variants in suspected COVID-19 PCR (-) patients

For COVID-19 (Coronavirus Disease-2019) cases, detecting host-based factors that predispose to infection is a very important research area. In this study, the aim is to investigate the MBL2 and NOS3 gene polymorphisms in COVID-19 patients with lung involvement, whose first nasopharyngeal PCR results were negative. Seventy-nine patients diagnosed with COVID-19 between April-June 2020 who were admitted to a university hospital, and 100 healthy controls were included. In the first statistical analysis performed between PCR-positive, CT-negative and PCR-negative, CT-positive patients; the AB of MBL2 genotype was significantly higher in the first group (p = 0.049). The B allele was also significantly higher in the same subgroup (p = 0.001). The absence of the AB genotype was found to increase the risk of CT positivity by 6.9 times. The AB genotype of MBL2 was higher in healthy controls (p = 0.006). The absence of the AB genotype was found to increase the risk of CT positivity; also, it can be used for early detection and isolation of patients with typical lung involvement who had enough viral loads, but whose initial PCR results were negative.

Mannose-binding lectin (MBL) in adult patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) refers to disorders associated with progressive inflammatory processes in the gastrointestinal system. IBD consists of two major forms, Crohn's disease (CD), and ulcerative colitis (UC). IBD became a global disease in the 21^st century. Its pathogenesis is still not fully understood. Mannose-binding lectin (MBL) is a pattern-recognising molecule, involved in anti-microbial and anti-cancer immunity. It is able to opsonize microorganisms and abnormal host cells, and to initiate complement activation. The aim of this study was to investigate possible involvement of MBL in inflammatory bowel disease in adults. Forty persons diagnosed with CD and 28 with ulcerative colitis were recruited. The control group consisted of 136 healthy persons. Single nucleotide polymorphisms of the MBL2 gene (localised to both promoter and exon 1) were determined as were serum MBL concentrations. The exon 1 variant alleles and MBL deficiency-associated genotypes were more frequent among patients compared with controls, although this difference was not statistically significant. No differences of MBL levels were found between the major groups. However in MBL2 A/A homozygous IBD patients, the median was significantly higher than in corresponding healthy subjects. That was particularly evident in the case of active Crohn's disease (1493 ng/ml vs. 800 ng/ml, p = 0.021). It may suggest that MBL and MBL-dependent complement activation contributes to excessive inflammation and its adverse effects in the course of CD. It cannot also be excluded that high MBL activity constitutes in some cases part of a multifactorial network conducing to development of CD.

The intestinal complement system in inflammatory bowel disease: Shaping intestinal barrier function

The complement system is part of innate sensor and effector systems such as the Toll-like receptors (TLRs). It recognizes and quickly systemically and/or locally respond to microbial-associated molecular patterns (MAMPs) with a tailored defense reaction. MAMP recognition by intestinal epithelial cells (IECs) and appropriate immune responses are of major importance for the maintenance of intestinal barrier function. Enterocytes highly express various complement components that are suggested to be pivotal for proper IEC function. Appropriate activation of the intestinal complement system seems to play an important role in the resolution of chronic intestinal inflammation, while over-activation and/or dysregulation may worsen intestinal inflammation. Mice deficient for single complement components suffer from enhanced intestinal inflammation mimicking the phenotype of patients with chronic inflammatory bowel disease (IBD) such as Crohn's disease (CD) or ulcerative colitis (UC). However, the mechanisms leading to complement expression in IECs seem to differ markedly between UC and CD patients. Hence, how IECs, intestinal bacteria and epithelial cell expressed complement components interact in the course of IBD still remains to be mostly elucidated to define potential unique patterns contributing to the distinct subtypes of intestinal inflammation observed in CD and UC.

Changes in the Expression and Distribution of Claudins, Increased Epithelial Apoptosis, and a Mannan-Binding Lectin-Associated Immune Response Lead to Barrier Dysfunction in Dextran Sodium Sulfate-Induced Rat Colitis

Background/Aims

This animal study aimed to define the underlying cellular mechanisms of intestinal barrier dysfunction.

Methods

Rats were fed 4% with dextran sodium sulfate (DSS) to induce experimental colitis. We analyzed the sugars in 24-hour urine output by high pressure liquid chromatography. The expression of claudins, mannan-binding lectin (MBL), and MBL-associated serine proteases 2 (MASP-2) were detected in the colonic mucosa by immunohistochemistry; and apoptotic cells in the colonic epithelium were detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method assay.

Results

The lactulose and sucralose excretion levels in the urine of rats with DSS-induced colitis were significantly higher than those in the control rats. Mannitol excretion was lower and lactulose/mannitol ratios and sucralose/mannitol ratios were significantly increased compared with those in the control group (p<0.05). Compared with the controls, the expression of sealing claudins (claudin 3, claudin 5, and claudin 8) was significantly decreased, but that of claudin 1 was increased. The expression of pore-forming claudin 2 was upregulated and claudin 7 was downregulated in DSS-induced colitis. The epithelial apoptotic ratio was 2.8%±1.2% in controls and was significantly increased to 7.2%±1.2% in DSS-induced colitis. The expression of MBL and MASP-2 in the intestinal mucosa showed intense staining in controls, whereas there was weak staining in the rats with colitis.

Conclusions

There was increased intestinal permeability in DSS-induced colitis. Changes in the expression and distribution of claudins, increased epithelial apoptosis, and the MASP-2-induced immune response impaired the intestinal epithelium and contributed to high intestinal permeability.

Peripheral Lymphoid Volume Expansion and Maintenance Are Controlled by Gut Microbiota via RALDH+ Dendritic Cells

Lymphocyte homing to draining lymph nodes is critical for the initiation of immune responses. Secondary lymphoid organs of germ-free mice are underdeveloped. How gut commensal microbes remotely regulate cellularity and volume of secondary lymphoid organs remains unknown. We report here that, driven by commensal fungi, a wave of CD45(+)CD103(+)RALDH(+) cells migrates to the peripheral lymph nodes after birth. The arrival of these cells introduces high amounts of retinoic acid, mediates the neonatal to adult addressin switch on endothelial cells, and directs the homing of lymphocytes to both gut-associated lymphoid tissues and peripheral lymph nodes. In adult mice, a small number of these RALDH(+) cells might serve to maintain the volume of secondary lymphoid organs. Homing deficiency of these cells was associated with lymph node attrition in vitamin-A-deficient mice, suggesting a perpetual dependence on retinoic acid signaling for structural and functional maintenance of peripheral immune organs.

Complement Activation by Giardia duodenalis Parasites through the Lectin Pathway Contributes to Mast Cell Responses and Parasite Control

Infection with Giardia duodenalis is one of the most common causes of diarrheal disease in the world. While numerous studies have identified important contributions of adaptive immune responses to parasite control, much less work has examined innate immunity and its connections to the adaptive response during this infection. We explored the role of complement in immunity to Giardia using mice deficient in mannose-binding lectin (Mbl2) or complement factor 3a receptor (C3aR). Both strains exhibited delayed clearance of parasites and a reduced ability to recruit mast cells in the intestinal submucosa. C3aR-deficient mice had normal production of antiparasite IgA, butex vivo T cell recall responses were impaired. These data suggest that complement is a key factor in the innate recognition of Giardia and that recruitment of mast cells and activation of T cell immunity through C3a are important for parasite control.

Mannose-binding lectin gene polymorphism and chronic hepatitis B infection in children

BACKGROUND/AIMS

Mannose-binding lectin (MBL) is a member of innate immune system that activates complement system through lectin pathway. MBL deficiency is associated with susceptibility to infectious diseases. In this study, the relation between MBL gene polymorphism and chronic hepatitis B infection in children is evaluated.

PATIENTS AND METHODS

The study included 67 children with chronic hepatitis B and 99 healthy controls. The hepatitis B patients were divided into immuntolerant, chronic inactive, and treatment groups according to their laboratory findings. MBL gene codon 52, 54, and 57 polymorphisms were studied with polymerase chain reaction in all patients and controls. The associations of MBL gene polymorphism with clinical, laboratory, and histopathologic findings were evaluated.

RESULTS

Homozygous codon 54 polymorphism of MBL was found significantly higher in chronic hepatitis B patients than controls. Rate of the polymorphism was similar in all groups and, responsive and nonresponsive patients in the treatment group.

CONCLUSIONS

The hepatitis B patients who are homozygous for codon 54 of MBL are prone to develop chronic infection. Longitudinal studies with larger groups are needed.

The complement system in inflammatory bowel disease

Complement is well appreciated to be a potent innate immune defense against microbes and is important in the housekeeping act of removal of apoptotic and effete cells. It is also understood that hyperactivation of complement, or the lack of regulators, may underlie chronic inflammatory diseases. A pipeline of products to intervene in complement activation, some already in clinical use, is being studied in various chronic inflammatory diseases. To date, the role of complement in inflammatory bowel disease has not received a lot of research interest. Novel genetically modified laboratory animals and experiments using antagonists to complement effector molecules have kindled important research observations implicating the complement system in inflammatory bowel disease pathogenesis. We review the evidence base for the role and potential therapeutic manipulation of the complement cascade in inflammatory bowel disease.

Low mannose-binding lectin (MBL) is associated with paediatric inflammatory bowel diseases and ileal involvement in patients with Crohn disease

BACKGROUND

Mannose-binding lectin (MBL) is a pattern-recognition molecule of the innate immune system and may be involved in the pathogenesis of inflammatory bowel disease (IBD). Our aim was to assess the prevalence of MBL deficiency in a cohort of patients with paediatric-onset IBD and study whether it is associated with the clinical manifestations, serum antibody formation, or genetic factors.

METHODS

This prospective study included 159 paediatric patients (mean age: 14.0 years) with IBD [107 patients with Crohn disease (CD) and 52 patients with ulcerative colitis (UC)]. Furthermore, 95 controls were investigated. Serum samples were determined for MBL by enzyme-linked immunosorbent assay (ELISA) and for serologic markers [autoantibodies against Saccharomyces cerevisiae (ASCA) and perinuclear components of neutrophils (pANCA)] by indirect immunofluorescent assay. NOD2/CARD15 variants were tested by polymerase chain reaction/restriction fragment length polymorphism.

RESULTS

The MBL serum concentration was significantly lower in IBD patients(both with CD and UC) compared to controls (IBD, p=0.007, CD, p=0.04, UC p=0.004). Prevalence of low MBL level (<500 ng/mL) was significantly higher in both CD and UC groups compared to controls (p=0.002 and p=0.006). Furthermore, low MBL level was associated with isolated ileal involvement (p=0.01) and MBL deficiency (<100 ng/mL) with male gender (p=0.004) in patients with CD. We failed to confirm any correlation between MBL deficiency and serum autoantibodies or NOD2/CARD15 variants.

CONCLUSIONS

Our results suggest that low MBL associated with paediatric-onset IBD and ileal CD may be considered an additional marker of the IBD pathogenesis.

Pattern recognition receptors--molecular orchestrators of inflammation in inflammatory bowel disease

Pattern recognition receptors (PRRs) are a family of germline encoded receptors responsible for the detection of "pathogen associated molecular patterns" (PAMPs) or host derived "damage associated molecular patterns" (DAMPs) which induce innate immune signalling to generate a pro-inflammatory profile within the host. Four main classes of PRRs are recognised, Toll-like receptors (TLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs) and C-type lectin receptors (CLRs). Abnormal activation of PRRs has been implicated in various autoimmune and inflammatory conditions including rheumatoid arthritis and asthma. Recent growing evidence has implicated these PRRs as contributory elements to the pathogenesis of inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Here, the current literature which implicates PRRs in IBD and CAC is comprehensively reviewed.

Complement-dependent injury and protection in a murine model of acute dextran sulfate sodium-induced colitis

Complement plays a key role in the pathophysiology of many inflammatory diseases, and in this study, we investigated the role of complement in the pathogenesis of inflammatory bowel disease. Compared to wild-type mice, mice deficient in C3 or factor B were protected from acute dextran sulfate sodium (DSS)-induced colitis. C1q/mannose-binding lectin (MBL) double-deficient mice, however, exhibited more severe colitis than wild-type mice. When mice were allowed to recover after DSS treatment, all C1q/MBL(-/-) mice died by day 2 of recovery period, and, surprisingly, all C3(-/-) and factor B(-/-) mice died by day 5. Serum endotoxin levels were significantly increased in complement-deficient mice prior to death, particularly in C1q/MBL(-/-) mice, and antibiotic treatment prevented the lethal effect of DSS in all complement-deficient mice. In contrast to complement deficiency, targeted complement inhibition with either complement receptor 2 (CR2)-Crry (blocks all pathways at C3 activation) or CR2-factor H (blocks alternative pathway) was highly protective at treating established acute colitis. Endotoxin levels remained low in complement-inhibited mice, and complement inhibition also reduced inflammatory cytokines, leukocyte infiltration, and tissue injury while improving wound repair and mucosal healing. CR2-factor H provided more effective protection than CR2-Crry. Thus, complement has both pathogenic and protective roles in acute DSS-induced colitis, and whereas the alternative pathway appears to play a key role in tissue inflammation and injury, the classical/lectin pathway provides important protection in terms of host defense and wound repair. Targeted inhibition of the alternative pathway may represent a therapeutic modality for treating acute phases of inflammatory bowel disease.

MBL Deficiency as Risk of Infection and Autoimmunity

In pathogen recognition by C-type lectins, several levels of complexity can be distinguished; these might modulate the immune response in different ways. Firstly, the pathogen-associated molecular pattern repertoire expressed at the microbial surface determines the interactions with specific receptors (Fig. 42.1). Secondly, each immune cell type possesses a specific set of pathogen-recognition receptors. Thirdly, changes in the cell-surface distribution of C-type lectins regulate carbohydrate binding by modulating receptor affinity for different ligands. Crosstalk between these receptors results in a network of multimolecular complexes, adding a further level of complexity in pathogen recognition (Cambi and Figdor 2005; Thiel et al. 2006) (see 10.1007/978-3-7091-1065-2_23). MBL deficiency is genetically determined and predisposes to recurrent infections and chronic inflammatory diseases. MBL deficiency has been implicated in susceptibility and course of viral, bacterial, fungal, and protozoan infection. More than 10% of the general population may, depending on definition, be classified as MBL deficient, underlining the redundancy of the immune system. MBL-disease association studies have been a fruitful area of research, which implicates a role for MBL in infective, inflammatory and autoimmune disease processes. MBL deficiency predisposes both to infection by extra-cellular pathogens and to autoimmune disease.

Mannan-binding lectin deficiency in pediatric patients with inflammatory bowel disease

OBJECTIVE

The incidence of inflammatory bowel disease (IBD) in Europe has increased significantly. At least a fourth of patients are children. Mannan-binding lectin (MBL) is believed to be an important component of innate immunity, acting as an opsonin and activator of the lectin pathway (LP) of complement. The data relating any of the LP factors to IBD are sparse and contradictory and were obtained mainly from adult patients. The aim of this study was to investigate the possible role of MBL in Crohn's disease (CD) and ulcerative colitis (UC) in children.

METHODS

MBL2 gene single nucleotide polymorphisms (PCR-RFLP) and MBL concentrations (ELISA) were determined.

RESULTS

The frequency of MBL2 gene variants responsible for MBL deficiency (LXPA/O and O/O) is significantly higher in CD patients compared with controls or children with UC. A relatively high frequency of the codon 52 mutation (D allele) was noted in these patients. Practically no difference was found between UC and control (C) groups. Similarly, the average MBL levels as well as the number of MBL-deficient (MBL concentrations < 150 ng/ml) individuals differed between CD patients and controls or children suffering from UC. Again, there was no difference between UC and C groups.

CONCLUSIONS

These data suggest that MBL deficiency may be associated with CD but not with UC in pediatric patients. The possible role of MBL in IBD requires confirmation in larger series and further investigation of the mechanisms involved.

Functional analysis of agalactosyl IgG in inflammatory bowel disease patients

BACKGROUND

Agalactosyl immunoglobulin (Ig) G is increased in inflammatory bowel disease (IBD) similarly to rheumatoid arthritis (RA). The lectin complement pathway is shown to be activated through association of agalactosyl IgG with mannan-binding lectin (MBL) in RA. Functional changes of IgG agalactosylation in IBD, however, have not yet been clarified.

METHODS

The ratio of the agalactosyl/non-agalactosyl fraction in fucosylated IgG oligosaccharides (G0F/G2F) and serum MBL levels were analyzed in 59 patients with Crohn's disease (CD), 64 ulcerative colitis (UC), and 39 healthy volunteers (HV). The MBL levels associated with serum IgG were analyzed by enzyme-linked immunosorbent assay. MBL expression in the intestinal mucosa was analyzed by immunohistochemistry. Phagocytosis of sheep red blood cells (SRBC) reacted with either an agalactosyl or non-agalactosyl SRBC-specific IgG antibody was determined by flow cytometry.

RESULTS

The serum MBL levels were not significantly different among CD, UC, or HV. In patients with CD, the serum MBL levels were negatively correlated with the Crohn's Disease Activity Index (CDAI). The levels of MBL associated with agalactosyl IgG were not different from those associated with non-agalactosyl IgG. Immunoreactivity to MBL was less in the inflamed mucosa compared with the noninflamed mucosa. Phagocytic activity of SRBC was significantly higher in the presence of agalactosyl IgG compared to non-agalactosyl IgG.

CONCLUSIONS

Agalactosyl IgG oligosaccharides enhanced antibody-dependent phagocytosis in vitro but did not activate the lectin complement pathway. Oligosaccharide alterations of IgG are not only a marker of IBD but also functionally modulate the immune function of IBD.

Association of genetic variants of mannan-binding (MBL) lectin-2 gene, MBL levels and function in ulcerative colitis and Crohn's disease

Ulcerative colitis and Crohn's disease are the two major forms of inflammatory bowel disease (IBD). A series of reports have hypothesized interplay of genetic and environmental factors in the pathogenesis of IBD. Polymorphism in the mannan-binding lectin-2 (MBL-2) gene is known to affect the structural assembly and function thereby predisposing subjects to various diseases. The present study was designed to evaluate effect of MBL-2 gene polymorphism on MBL levels and function in IBD patients. Genomic DNA was isolated from blood samples collected from 157 ulcerative colitis, 42 Crohn's disease and 204 control subjects. Genotyping for different polymorphic sites at exon1 of MBL-2 gene was performed by refractory mutation system-PCR and amplification followed by restriction digestion (PCR-RFLP). Serum MBL concentration and C4 deposition levels were estimated using ELISA. Mannan-binding lectin-2 genotypic variants were calculated in IBD and healthy controls. The frequency of single nucleotide polymorphisms at codon 54 was significantly higher in ulcerative colitis patients than controls (P < 0.0001). Ulcerative colitis patients with 'codon 54'-variation showed low serum MBL concentrations coupled with altered MBL function compared to controls. In conclusion, single nucleotide polymorphism in the MBL-2 gene is an important risk factor significantly affecting MBL levels and function in the development of ulcerative colitis among Indians.

Mannose-binding lectin level and deficiency is not associated with inflammatory bowel diseases, disease phenotype, serology profile, and NOD2/CARD15 genotype in a large Hungarian cohort

Mannose-binding lectin (MBL) is a major, soluble, pattern-recognition molecule and an important component of the innate host defense. The role of MBL in inflammatory bowel diseases (IBDs) is controversial. We determined the prevalence of MBL deficiency in a Hungarian IBD patients' cohort, and whether it is associated with the antimicrobial antibody formation or particular clinical manifestations. Nine hundred ninety IBD patients and 225 healthy subjects were investigated. Sera were assayed for MBL and a panel of antimicrobial antibodies (anti-OMP, anti-Saccharomyces cerevisiae antibodies, and antiglycans) by ELISA. TLR4 and NOD2/CARD15 variants were tested by polymerase chain reaction/restriction fragment length polymorphism. Median MBL level was not significantly different between IBDs (Crohn's disease [CD]: 929; ulcerative colitis [UC]: 810 ng/ml) and the control group (1027 ng/ml), as well as the prevalence of absolute MBL deficiency (<100 ng/ml) (CD: 15.0%, UC: 18.4%, controls: 15.6%). The presence of a low MBL level (<500 ng/ml) was not associated with any of the examined serologic markers, or their combinations. In addition, there was no association with the clinical presentation, disease course, or response to treatment. TLR4 variant genotype was more common in CD patients without MBL deficiency (11% vs. 1.7%, OR: 7.29, 95% CI: 1.08-53.9, p = 0.02). We failed to confirm any association between MBL deficiency and serologic marker positivity. MBL deficiency was not predictive for clinical phenotype or disease activity in IBDs.

The increased mucosal mRNA expressions of complement C3 and interleukin-17 in inflammatory bowel disease

Recent studies have demonstrated that the complement system participates in the regulation of T cell functions. To address the local biosynthesis of complement components in inflammatory bowel disease (IBD) mucosa, we investigated C3 and interleukin (IL)-17 mRNA expression in mucosal samples obtained from patients with IBD. The molecular mechanisms underlying C3 induction were investigated in human colonic subepithelial myofibroblasts (SEMFs). IL-17 and C3 mRNA expressions in the IBD mucosa were evaluated by real-time polymerase chain reaction. The C3 levels in the supernatant were determined by enzyme-linked immunosorbent assay. IL-17 and C3 mRNA expressions were elevated significantly in the active lesions from ulcerative colitis (UC) and Crohn's disease (CD) patients. There was a significant positive correlation between IL-17 and C3 mRNA expression in the IBD mucosa. IL-17 stimulated a dose- and time-dependent increase in C3 mRNA expression and C3 secretion in colonic SEMFs. The C3 molecules secreted by colonic SEMFs were a 115-kDa alpha-chain linked to a 70-kDa beta-chain by disulphide bonds, which was identical to serum C3. The IL-17-induced C3 mRNA expression was blocked by p42/44 mitogen-activated protein kinase (MAPK) inhibitors (PD98059 and U0216) and a p38 MAPK inhibitor (SB203580). Furthermore, IL-17-induced C3 mRNA expression was inhibited by an adenovirus containing a stable mutant form of I kappaB alpha. C3 and IL-17 mRNA expressions are enhanced, with a strong correlation, in the inflamed mucosa of IBD patients. Part of these clinical findings was considered to be mediated by the colonic SEMF response to IL-17.

Lack of genetic association of promoter and structural variants of mannan-binding lectin (MBL2) gene with susceptibility to generalized vitiligo

BACKGROUND

Vitiligo is a common depigmenting disorder resulting from the loss of functional melanocytes in the skin. It is hypothesized to be of autoimmune origin. Mannan-binding lectin (MBL) plays an important role in innate immunity. It helps in the clearance of apoptotic cells and in complement activation. Genetic variability due to structural and promoter polymorphisms in the MBL2 gene has been reported to be associated with increased risk for several autoimmune diseases including vitiligo.

OBJECTIVES

The aim of this study was to explore whether MBL2 structural and promoter polymorphisms are associated with generalized vitiligo in Gujarat where the prevalence of vitiligo is alarmingly high.

MATERIALS AND METHODS

We undertook a case-control study to investigate the association of MBL2 gene exon 1 polymorphisms - codon 52, codon 54 and codon 57 as well as promoter -221 polymorphism in 92 patients with generalized vitiligo and 94 unaffected age-matched controls by polymerase chain reaction-heteroduplex analysis.

RESULTS

The genotype and allele frequencies of MBL2 structural and promoter polymorphisms did not differ significantly between the control and patient population (P-values: P < 0.019 for codon 52, P < 0.373 for codon 54, P < 0.855 for codon 57 and P < 0.889 for -221 promoter polymorphisms) after Bonferroni's correction for multiple testing, which suggests that there is no association of MBL2 structural and promoter polymorphisms with generalized vitiligo.

CONCLUSIONS

Our results suggest that the well-documented structural and promoter polymorphisms of the MBL2 gene may not be associated with generalized vitiligo in the Gujarat population.

Bench-to-bedside review: Association of genetic variation with sepsis

Susceptibility and response to infectious disease is, in part, heritable. Initial attempts to identify the causal genetic polymorphisms have not been entirely successful because of the complexity of the genetic, epigenetic, and environmental factors that influence susceptibility and response to infectious disease and because of flaws in study design. Potential associations between clinical outcome from sepsis and many inflammatory cytokine gene polymorphisms, innate immunity pathway gene polymorphisms, and coagulation cascade polymorphisms have been observed. Confirmation in large, well conducted, multicenter studies is required to confirm current findings and to make them clinically applicable. Unbiased investigation of all genes in the human genome is an emerging approach. New, economical, high-throughput technologies may make this possible. It is now feasible to genotype thousands of tag single nucleotide polymorphisms across the genome in thousands of patients, thus addressing the issues of small sample size and bias in selecting candidate polymorphisms and genes for genetic association studies. By performing genome-wide association studies, genome-wide scans of nonsynonymous single nucleotide polymorphisms, and testing for differential allelic expression and copy number polymorphisms, we may yet be able to tease out the complex influence of genetic variation on susceptibility and response to infectious disease.

Increased risk of both ulcerative colitis and Crohn's disease in a population suffering from COPD

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation of the airways. In the majority of cases, the inflammation is triggered by tobacco smoke. Smoking also affects the pathogenesis of inflammatory bowel disease (IBD), protecting against ulcerative colitis (UC) and promoting development of Crohn's disease (CD). The present study was undertaken to investigate occurrence of IBD among COPD patients, indicating common inflammatory pathways and shared vulnerability on a genetic basis. The study was designed as a population-based cohort study. All individuals discharged with a diagnosis of COPD from 1987 to 2002 were identified in the Swedish Inpatient Register (n=180,239). Controls and first-degree relatives of both cases and controls were identified using the Multi-Generation Register. Finally, all individuals (n=1,174,557) were compared with the Inpatient Register, identifying discharges with a diagnosis of UC or CD. Hazard ratios (HR) for IBD were determined by Cox proportional hazards regression analysis. COPD patients had a significantly higher risk of both UC (HR 1.83; 95% CI 1.61-2.09) and CD (HR 2.72; 95% CI 2.33-3.18). Among first-degree relatives of COPD patients, there was also an overall increased risk of CD (HR 1.25; 95% CI 1.09-1.43) but not of UC (HR 1.09; 95% CI 0.96-1.23). The kinship of first-degree relatives displayed an increased risk of both UC and CD among siblings (HR 1.49; 95% CI 1.15-1.91 and HR 1.46; 95% CI 1.12-1.89, respectively). The results suggest that COPD and IBD may have inflammatory pathways in common, including genetic variants of genes predisposing for disease.

The Role of Mannan-Binding Lectin (MBL) Gene Polymorphism in Ulcerative Colitis

Series studies suggest that enteropathogenic microorganisms play a substantial role in the clinical initiation and relapses of ulcerative colitis (UC). Mannan-binding lectin (MBL) is an important constituent of the innate immune system, and deficiency of MBL has been reported to increase the overall susceptibility of an individual to infectious disease. This study was aimed to investigate the associations between polymorphisms of the MBL gene and UC. Recruited in this study were 108 Japanese patients with UC and 144 healthy control subjects. Polymorphism at codon 54 of exon 1 of the MBL gene was investigated by polymerase chain reaction based restriction fragment length polymorphism. In general, no significant difference in MBL polymorphism was found between UC patients and health controls. However, the frequency of A carriers was significantly higher in the relapsing cases than controls (Odds ration = 2.19, 95%CI, 1.10-4.34; p = 0.023), and similar tendency was also found in A/A genotype. In conclusion, the polymorphism at codon 54 of exon 1 of the MBL gene associated with the susceptibility to the relapsing phenotype of ulcerative colitis. It suggests that codon 54 A variants of MBL gene may have an increased risk for the flare-ups of UC.

Serum mannan-binding lectin levels in patients with celiac disease: an analysis of clinical and autoimmune features

Mannan-binding lectin (MBL) is the central protein in the activation of complement through the lectin pathway. MBL plasma concentration is genetically determined and varies significantly among individuals. Recent findings suggest that MBL is associated with the pathogenesis of celiac disease (CD). In this study, MBL and C-reactive protein (CRP) levels were determined in 101 celiac patients and 120 controls, with the aim to associate with the presence of gluten in the diet, disease severity, and the presence of concomitant autoimmune diseases. MBL concentration was determined by ELISA and CRP by nephelometry, using a high-sensitivity method. EmA-IgA and other autoantibodies were tested by indirect immunofluorescence. Although a significant increase in MBL levels was observed in male patients compared to female (P = 0.024), the absence of any other association suggests that circulating MBL and CRP concentrations are not associated with clinical and autoimmune CD features in Brazilian patients.

Genetics of the innate immune response in inflammatory bowel disease

The discovery of nucleotide-binding oligomerization domain 2/caspase recruitment domain-containing protein 15 (NOD2/CARD15) as the first susceptibility gene in Crohn's disease (CD) has shifted the focus of research into the pathogenesis of inflammatory bowel disease (IBD) firmly to the innate immune response and the integrity of the epithelial barrier. The subsequent implication in IBD of variant alleles of OCTN, DLG5, MDR1, and TLRs has provided further support for a new, more complex model of innate immunity function in the gastrointestinal tract. In this review, we examine the recent advances in our understanding of the influence of genetics of the innate immune response on IBD. We will focus on germline variation of genes encoding pathogen-recognition receptors, proteins involved in epithelial homeostasis and secreted antimicrobial proteins.

Genetic susceptibility to total hip arthroplasty failure--positive association with mannose-binding lectin

Mannose-binding lectin (MBL) may be involved in the biologic cascade of events initiated by wear debris and bacterial infection around loosened total hip arthroplasties (THAs). Individual responses to such stimuli may be dictated by genetic variation caused by single nucleotide polymorphisms (SNPs). We performed a case-control study on 4 MBL SNPs using case patients (n = 91) with aseptic loosening or deep infection (n = 71). Control subjects (n = 150) had clinically and radiologically well-fixed THAs for more than 10 years. Frequency of the C allele (P = .001) and that of the genotype C/C (P = .004) for the -550 SNP were associated with aseptic failure. The codon 54 SNP G allele (P = .012) and G/G genotype (P = .027) frequencies were associated with aseptic failure as well. In the septic group, the frequency of the C allele (P = .01) and that of the genotype C/C (P = .05) for the -550 SNP were significant. Failure of THAs may be under genetic influence to candidate susceptibility genes such as MBL.

Mannose-binding lectin and maladies of the bowel and liver

Mannose-binding lectin (MBL) is a pattern-recognition molecule that binds to characteristic carbohydrate motifs present on the surface of many different pathogens. MBL binding stimulates the immune system via the lectin pathway of complement activation. In certain clinical situations, often characterized by pre-existing immune compromise, MBL deficiency increases the risk of infectious and other disease-specific complications. Many of the key pathogenic processes inherent to common gastroenterological diseases, such as infection, immunological damage, and carcinogenesis, have been linked to MBL. This editorial reviews the biology of MBL, outlines key disease associations to document the breadth of influence of MBL, and finally, highlights the relevance of MBL to both gastroenterological health and disease.

Mannose-binding lectin contributes to the severity of Guillain-Barré syndrome

In Guillain-Barré syndrome (GBS), complement activation plays a crucial role in the induction and extent of the postinfectious immune-mediated peripheral nerve damage. Mannose-binding lectin (MBL) activates the complement system via the lectin pathway after recognition of repetitive sugar groups on pathogens. We investigated whether the MBL2 genotype, serum MBL level, and MBL complex activity are associated with the development and severity of GBS. Single nucleotide polymorphisms in the promoter region (-550 H/L and -221 X/Y) and exon 1 (A/O) of the MBL2 gene were determined in 271 GBS patients and 212 healthy controls. The frequencies of the H allele, HY promoter haplotype, and HYA haplotype, which are related to high MBL activity, were all increased in GBS patients compared with healthy controls (p < or = 0.03), particularly in severely affected GBS patients (MRC-sum score < 40) (p < or = 0.02). Severe weakness was also associated with high MBL concentrations and MBL complex activity in sera from GBS patients (p < 0.01). The MBL2 B allele was associated with functional deficiency and relatively mild weakness. These results support the hypothesis that complement activation mediated by MBL contributes to the extent of nerve damage in GBS, which is codetermined by the MBL2 haplotype.

Glomerular activation of the lectin pathway of complement in IgA nephropathy is associated with more severe renal disease

IgA nephropathy (IgAN) is characterized by glomerular co-deposition of IgA and complement components. Earlier studies showed that IgA activates the alternative pathway of complement, whereas more recent data also indicate activation of the lectin pathway. The lectin pathway can be activated by binding of mannose-binding lectin (MBL) and ficolins to carbohydrate ligands, followed by activation of MBL-associated serine proteases and C4. This study examined the potential role of the lectin pathway in IgAN. Renal biopsies of patients with IgAN (n=60) showed mesangial deposition of IgA1 but not IgA2. Glomerular deposition of MBL was observed in 15 (25%) of 60 cases with IgAN and showed a mesangial pattern. All MBL-positive case, but none of the MBL-negative cases showed glomerular co-deposition of L-ficolin, MBL-associated serine proteases, and C4d. Glomerular deposition of MBL and L-ficolin was associated with more pronounced histologic damage, as evidenced by increased mesangial proliferation, extracapillary proliferation, glomerular sclerosis, and interstitial infiltration, as well as with significantly more proteinuria. Patients who had IgAN with or without glomerular MBL deposition did not show significant differences in serum levels of MBL, L-ficolin, or IgA or in the size distribution of circulating IgA. Furthermore, in vitro experiments showed clear binding of MBL to polymeric but not monomeric patient IgA, without a significant difference between both groups. Together, these findings strongly point to a role for the lectin pathway of complement in glomerular complement activation in IgAN and suggest a contribution for both MBL and L-ficolin in the progression of the disease.

Association of a new mannose-binding lectin variant with severe malaria in Gabonese children

Mannose-binding lectin (MBL2) variants that decrease the plasma level of the protein or encode dysfunctional proteins are frequently associated with the severity of a number of infections and autoimmune disorders. The high frequencies of these variants in most populations of the world are probably maintained by some selective advantage against widespread diseases. We found 14 new MBL2 allelic haplotypes, two of them with non-synonymous variants, by screening 136 children with uncomplicated malaria, 131 children with severe malaria and 39 older healthy schoolchildren. We also found a significant association of a novel variant with susceptibility to severe malaria (P=0.010). Increased MBL plasma levels and corresponding MBL2 genotypes were associated with lower concentration of several cytokines and chemokines in plasma of malaria patients. We suggest that malaria could have been one of the evolutionary driving forces shaping the MBL2 polymorphism in the African population.

Clinical manifestations of mannan-binding lectin deficiency

Mannan-binding lectin (MBL) is a plasma protein of the innate immune system with the ability to initiate antimicrobial and inflammatory actions. MBL deficiency is common. More than 10% of the general population may, depending on definition, be classified as MBL deficient, underlining the redundancy of the immune system. Ongoing research attempt to illuminate at which conditions MBL deficiency may lead to disease. With examples, this review illustrates the diversity of results obtained so far.

Complement activation capacity in plasma before and during high-dose prednisolone treatment and tapering in exacerbations of Crohn's disease and ulcerative colitis

Background

Ulcerative colitis (UC) and Crohn's disease (CD) are characterized by intestinal inflammation mainly caused by a disturbance in the balance between cytokines and increased complement (C) activation. Our aim was to evaluate possible associations between C activation capacity and prednisolone treatment.

Methods

Plasma from patients with exacerbations of UC (n = 18) or CD (n = 18) were collected before and during high dose prednisolone treatment (1 mg/kg body weight) and tapering. Friedman's two way analysis of variance, Mann-Whitney U test and Wilcoxon signed-rank sum test were used

Results

Before treatment, plasma from CD patients showed significant elevations in all C-mediated analyses compared to the values obtained from 38 healthy controls (p < 0.02), and in mannan binding lectin (MBL)-concentration and MBL-C4-activation capacity (AC) values compared to UC patients (p < 0.02). Before treatment, plasma from UC patients showed significant elevations only in the classical pathway-mediated C3-AC compared to values obtained from healthy controls (p < 0.01). After treatment was initiated, significant reductions, which persisted during follow-up, were observed in the classical pathway-mediated C3-AC and MBL-C4-AC in plasma from CD patients (p < 0.05).

Conclusion

Our findings indicate that C activation capacity is up-regulated significantly in plasma from CD patients. The decreases observed after prednisolone treatment reflect a general down-regulation in immune activation.

Mannose binding lectin level and polymorphism in patients on long-term peritoneal dialysis

BACKGROUND

Infection is a leading cause of mortality and morbidity in patients with end-stage renal disease. The increased susceptibility to infection is probably secondary to the impaired immune defence in uraemia and other co-morbid factors such as diabetes mellitus. Peritonitis remains the most common and major complication in the treatment modality of peritoneal dialysis (PD) for uraemic patients. Mannose binding lectin (MBL) is a calcium dependent C-type lectin that acts as an important first line defence mechanism against infection by its capability to activate the complement system and enhance phagocytosis.

METHODS

We examined whether serum concentration of MBL and the point mutation of MBL may act as a risk factor in PD-related peritonitis. We studied four groups of dialysis patients: PD patients with two or more episodes of peritonitis, peritonitis-free PD patients, haemodialysis (HD) patients not previously on PD, and HD patients who were converted from PD due to technique failure following peritonitis-related abdominal adhesion. Results. Both homozygous and heterozygous patients had profoundly reduced serum level of MBL. The codon 54 point mutation rate amongst our dialysis patients was comparable with that of healthy subjects. Dialysis patients had a significantly lower serum level of MBL than healthy controls independent of the MBL gene mutation or the mode of dialysis treatment. Patients on PD with codon 54 point mutation were found to have a lower serum MBL level compared with HD patients with similar MBL gene mutation. However, we found no difference in the serum MBL level or frequency of codon 54 point mutation between four groups of dialysis patients.

CONCLUSIONS

Dialysis patients have lower MBL levels that may increase the susceptibility of infection. However, the existence of other risk factors such as connection technique, nasal bacterial carriers, bowel pathology and personal hygiene precludes the MBL level as the sole primary factor for peritonitis in patients on maintenance PD treatment.

Association between mannose-binding lectin levels and graft survival in kidney transplantation

The mannose-binding lectin (MBL) pathway of complement is activated by pattern recognition. Genetic MBL variants are frequent and associated with low MBL serum levels. Higher MBL levels may be associated with more complement-mediated damage resulting in inferior graft survival. Pre-transplant serum samples from 266 consecutive deceased donor kidney transplant recipients were analyzed for MBL concentration by ELISA. Subsequently the cohort was analyzed for transplant-related outcome. There was no significant difference in incidence of delayed graft function in recipients with a low MBL level (< or =400 ng/mL) compared to those with a higher MBL level (>400 ng/mL) (37.1 vs. 34.9%). At 10 years, death-censored graft survival was 89.9% in patients with an MBL level below 400 ng/mL compared with 78.8% at a higher MBL level (p < 0.02). Multivariate analysis including traditional risk factors for graft loss showed an independent risk of 2.7 (95% CI 1.2-6.3) for death-censored graft loss if pre-transplant MBL levels were above 400 ng/mL. This difference was almost entirely explained by rejection-associated graft loss (2.4 vs. 12.4%, p < 0.01). Higher MBL levels seem to be associated with a more severe form of rejection leading to treatment failure and graft loss. If these data can be confirmed, pre-transplant MBL levels may provide additional information for risk stratification prior to kidney transplantation.

Evidence of a correlation between mannose binding lectin and celiac disease: a model for other autoimmune diseases

Celiac disease is a multifactorial disorder caused, in genetically susceptible patients, by the ingestion of dietary gluten. Very little is known about the genetic factors, but there is a strong association of two HLA haplotypes (DQ2 or alpha1*05, beta1*02 and DQ8 or alpha1*0301, beta1*0302) with the disease. We investigated the relationship between polymorphisms in the first exon of the MBL2 gene, which encodes for mannose binding lectin (MBL) and celiac disease. Moreover we studied the MBL role by immunohistochemistry and TUNEL. Results were confirmed by clinical findings. We enrolled 149 Italian celiac patients; 116 were characterized by the presence of DQ2 or DQ8. The HLA haplotype was established by allelic specific PCR while the MBL2 genotype was resolved by melting temperature assay. Immunohistochemistry and TUNEL assays were performed on serial sections of biopsy specimens from celiac patients and healthy controls. MBL2 allele and genotype frequencies varied significantly between celiac patients and healthy controls. The frequencies of the 0 allele were 28% in DQ2 or DQ8 celiac patients, 36% in HLA atypical celiac patients, and 22% in healthy controls. Interestingly, the MBL2 0/0 genotype was present in 7 of 33 HLA atypical celiac patients (21%) and in 13 of 116 HLA typical celiac patients (13%) but in only 7 of 147 healthy controls (5%). Furthermore, we found that MBL2 genotype is strongly associated with the occurrence of secondary autoimmune diseases. Immunohistochemistry and TUNEL findings support a role of MBL2 in the clearance of apoptotic cells. In conclusion, MBL2 variants, responsible for lower MBL levels, are associated with celiac disease and higher risk of developing autoimmune diseases. Here we propose a role for MBL in the disease which could be easily applied to other autoimmune disorders.

Genetic variants of the mannan-binding lectin are associated with immune reactivity to mannans in Crohn's disease

BACKGROUND & AIMS

Some patients with Crohn's disease (CD) develop antibodies against mannan, a component of the yeast Saccharomyces cerevisiae cell wall. Mannan-binding lectin (MBL), a component of the innate immune system, can bind to S. cerevisiae . MBL concentration depends on genetic polymorphisms. The aim of this study was to evaluate whether low MBL contributes to anti-S. cerevisiae antibody (ASCA) production.

METHODS

ASCA and MBL concentrations in sera from patients with CD (n = 74), ulcerative colitis (UC) (n = 22), and healthy controls (n = 32) were measured by an enzyme-linked immunosorbent assay (ELISA). Genetic MBL variants were determined from 58 CD patients, 18 UC patients, and 47 controls by DNA sequencing. Lymphocytes were tested for proliferative response after stimulation with mannan.

RESULTS

ASCA were found in 47% of the patients with CD and in 0% of the controls. More ASCA-positive patients (52%) had low serum MBL concentrations compared with ASCA-negative patients (4%) (P < 0.0001). T-cell proliferation in response to mannan stimulation was observed in ASCA-positive patients and could be inhibited by the addition of MBL. These patients had significantly lower MBL serum concentrations than patients whose lymphocytes did not proliferate on mannan stimulation (P < 0.0001). Homozygous or compound heterozygous MBL mutations in the exon 1 and promoter occurred in 12 patients with cellular or humoral immune reactivity to mannan as compared with only 1 nonreactive patient (P < 0.0001).

CONCLUSIONS

A subgroup of CD patients is characterized by ASCA positivity, T-cell proliferation on mannan stimulation, and mutations in the MBL gene that result in MBL deficiency. Thus, we propose that enhanced mannan exposure stimulates specific immune responses in a subgroup of CD patients with genetically determined low MBL concentrations. This enhanced exposure contributes to the generation of ASCA.

Interleukin-1 receptor antagonist VNTR-polymorphism in inflammatory bowel disease

Both genetic and environmental factors have been implicated in the etiology of inflammatory bowel diseases (IBD) i.e., Crohn's disease (CD) and ulcerative colitis (UC). Polymorphisms in cytokine genes are likely to influence an individual's predisposition to IBD. In intron 2 of the interleukin-1 receptor antagonist (IL-1ra) gene, a variable number of an 86-bp tandem repeat (VNTR) polymorphism leads to the existence of five different alleles. In order to analyze the association between certain IL-1ra VNTR-alleles and IBD, we investigated the IL-1ra genotype and allele frequencies in 342 unrelated IBD patients and in 401 healthy control individuals. CD patients were also genotyped for the three main associated variants in the NOD2/CARD15 gene. In the IBD group, a significant decrease in the frequency of IL-1ra allele 1 (P=0.048) compared to controls was observed. The frequency of IL-1ra genotype 1/1 was significantly lower in the IBD population vs the control group (P=0.018). Analysis of the CD population without NOD2 homozygotes and compound heterozygotes revealed a more significant decrease in IL-1ra genotype 1/1 compared to controls (P=0.038). These results support the hypothesis that the IL-1ra VNTR-polymorphism could be among the genetic factors that are of importance in IBD susceptibility.