Mannose-binding lectin and rheumatoid arthritis in southern Chinese

Mannose-Binding Lectin Gene Variants as Disease Susceptibility Biomarkers in Rheumatoid Arthritis

Background: Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease characterized by progressive destruction of peripheral joints. About 1% of the human population worldwide is suffering from this disease. The pathophysiology of RA is largely being influenced by immune dysregulation. Mannose-binding lectin (MBL), an acute-phase protein, has been reported to play an important role in pathogenesis of RA by the activation of complement pathway. Various studies documented the established the role of MBL in pathogenesis of various autoimmune diseases, including RA. MBL protein is encoded by gene MBL2, mapped on chromosome 10q11.2-q21. Objective: Both MBL serum levels and activity are mainly determined genetically by its variants. So considering the putative clinical role of MBL2, this case-control association study was designed to assess its six functional variants in a northwestern Indian cohort. Methods: Genetic typing of six MBL2 variants was done by amplification refractory mutation system-polymerase chain reaction. Data were analyzed using suitable statistical tools. Results: Significant difference has been observed in genotypic and allelic distribution between cases and controls for rs11003125. Comparison of allelic distribution for rs1800450 showed significantly high prevalence of A allele in cases than controls. Conclusion: These results indicate that MBL2 variants may act as plausible marker for susceptibility toward RA. Keeping this in view, it is pertinent to screen these variants in other population groups of India.

At Early Rheumatoid Arthritis Stage, the Infectious Spectrum Is Driven by Non-Familial Factors and Anti-CCP Immunization

Background/Objectives: Patients with rheumatoid arthritis (RA) are prone to develop infections. Methods: Accordingly, 195 untreated early (e)RA patients and 398 healthy controls were selected from women in Tatarstan's cohort to study infectious history in the anamnesis (four criteria) and in the previous year (16 criteria). Information about annual infections was collected face-to-face from year to year by a qualified rheumatologist/general practitioner and included the active use of information from medical records. Results: In the anamnesis, tuberculosis, and pneumonia, and in the previous year, respiratory tract infections, skin infections, and herpes simplex virus reactivation incidence were reported to be increased in eRA patients, as well as the event number and duration of acute and chronic tonsillitis. Moreover, more bacterial-suspected upper respiratory infections and urinary tract infections were retrieved in sporadic eRA patients as compared to familial eRA patients. An elevated immunization against CCP prevented respiratory tract infection in those with HSV exacerbation. Finally, associations were retrieved between infection (event number/delay) and RA indices: (i) chronic tonsillitis exacerbations with disease activity and health assessment (HAQ) in familial eRA; (ii) bacterial-suspected upper respiratory infections with the number of swollen and tender joints in sporadic eRA; and (iii) HSV exacerbation with inflammation in eRA patients with negative/low response against CCP. Here, we demonstrate the complex nature of the interplay of RA with specific infections. Conclusions: For the first time, differences in the patterns of annual trivial infections and their links with RA indices were found in cohorts of familial and sporadic cases of the disease. Additionally, for the first time, we identified a remarkable relationship between early RA and exacerbations of chronic tonsillitis, as well as tuberculosis in the patient's history. Altogether, this study supports the existence of a complex interplay between infections and RA at onset driven by familial status and the presence of anti-CCP Ab at elevated levels.

Interplay of Environmental, Individual and Genetic Factors in Rheumatoid Arthritis Provocation

In this review, we explore systemization of knowledge about the triggering effects of non-genetic factors in pathogenic mechanisms that contribute to the development of rheumatoid arthritis (RA). Possible mechanisms involving environmental and individual factors in RA pathogenesis were analyzed, namely, infections, mental stress, sleep deprivation ecology, age, perinatal and gender factors, eating habits, obesity and smoking. The non-genetic factors modulate basic processes in the body with the impact of these factors being non-specific, but these common challenges may be decisive for advancement of the disease in the predisposed body at risk for RA. The provocation of this particular disease is associated with the presence of congenital loci minoris resistentia. The more frequent non-genetic factors form tangles of interdependent relationships and, thereby, several interdependent external factors hit one vulnerable basic process at once, either provoking or reinforcing each other. Understanding the specific mechanisms by which environmental and individual factors impact an individual under RA risk in the preclinical stages can contribute to early disease diagnosis and, if the factor is modifiable, might be useful for the prevention or delay of its development.

Effect of mannose-binding lectin gene polymorphisms on the risk of rheumatoid arthritis: Evidence from a meta-analysis

BACKGROUND

The effect of mannose-binding lectin (MBL) gene polymorphisms on susceptibility of rheumatoid arthritis (RA) were evaluated in ethnically different populations, whereas the results were always inconsistent.

MATERIALS AND METHODS

Fourteen articles involving 36 datasets were recruited to evaluate the association between MBL gene polymorphisms and rheumatoid arthritis in a meta-analysis. The random or fixed effect models were used to evaluate the pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs).

RESULTS

Stratified analysis by ethnicities was conducted and the result revealed that rs1800450 (T vs C, OR = 1.32, 95% CI: 1.04-1.67, P < .05) and MBL-A/O (T vs C, OR = 1.20, 95% CI: 1.08-1.34, P < .001) were strongly associated with RA in Brazilian populations. In addition, the significant relationship between rs11003125 (T vs C, OR = 1.16, 95% CI: 1.06-1.26, P < .05) with RA were also observed in East Asian populations. Meanwhile, the inverse associations between rs5030737 with RA in East Asians and rs1800450 with RA in Indians were acquired. However, no association between any MBL polymorphism with RA susceptibility was confirmed in Caucasians.

CONCLUSIONS

The structural polymorphisms in exon 1 of MBL gene may significantly contribute to susceptibility and development of RA in Brazilian and Indian populations, whereas the functional polymorphisms in the promoter region were more likely to associate with RA in East Asians.

Mannan-Binding Lectin Attenuates Inflammatory Arthritis Through the Suppression of Osteoclastogenesis

Mannan-binding lectin (MBL) is a vital element in the host innate immune system, which is primarily produced by the liver and secreted into the circulation. Low serum level of MBL is reported to be associated with an increased risk of arthritis. However, the underlying mechanism by which MBL contributes to the pathogenesis of arthritis is poorly understood. In this study, we investigated the precise role of MBL on the course of experimental murine adjuvant-induced arthritis (AIA). MBL-deficient (MBL^−/−) AIA mice showed significantly increased inflammatory responses compared with wild-type C57BL/6 AIA mice, including exacerbated cartilage damage, enhanced histopathological features and high level of tartrate-resistant acid phosphatase (TRAP)-positive cells. MBL protein markedly inhibited the osteoclast formation from human blood monocytes induced by receptor activator of nuclear factor-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) in vitro. Mechanistic studies established that MBL inhibited osteoclast differentiation via down-regulation of p38 signaling pathway and subsequent nuclear translocation of c-fos as well as activation of nuclear factor of activated T-cells c1 (NFATc1) pathway. Importantly, we have provided the evidence that concentrations of MBL correlated negatively with the serum levels of amino-terminal propeptide of type I procollagen (PINP) and C-terminal telopeptide of type I collagen (β-CTX), serum markers of bone turnover, in patients with arthritis. Our study revealed an unexpected function of MBL in osteoclastogenesis, thus providing new insight into inflammatory arthritis and other bone-related diseases in patients with MBL deficiency.

Cardiovascular risk and mannose binding lectin in patients with rheumatoid arthritis from southern Brazil

BACKGROUND

Mannose binding lectin (MBL) appears to be involved in susceptibility to rheumatoid arthritis (RA), in the inflammatory process and in the genesis of atherosclerotic disease.

OBJECTIVE

To study the association of MBL serum levels and its genotypic variation with carotid arteries intimal thickness (IMT) in RA patients from Southern Brazil.

METHODS

MBL serum levels, MBL2 genotyping and IMT were investigated in 90 RA patients along with their demographic, clinical and laboratory profile. MBL levels and MBL2 genotyping were evaluated in 90 healthy controls.

RESULTS

A significant lower MBL serum concentration was observed in patients with RA in relation to controls (528 ng/mL vs 937.5 ng/mL, p = 0.05, respectively). The median IMT in RA patients was 0.59 mm (0.51 to 0.85 mm). There was no correlation between levels of MBL with disease activity, erythrocyte sedimentation rate, autoantibodies presence or IMT (p = NS). A weak and negative correlation was found between MBL and CRP levels (Rho = -0.24; p = 0.02;). The MBL2 variant at codon 54 (variant B) and HYPA haplotype were the most frequently observed in the RA sample (67.5% and 31.7%). MBL2 wild type (A/A) were associated with lower IMT when compared with heterozygotes (A/O; p = 0.04) and low producers (O/O; p = 0.05). In addition, high producers genotypes had lower levels of CRP when compared with medium (p = 0.04) or with low producers (p = 0.05).

CONCLUSION

RA patients had lower MBL levels than controls. MBL were negatively associated with CRP serum levels; low MBL genotypes producers increased thickness of the IMT than high producers.

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

Antibodies to mannose binding lectin in patients with systemic lupus erythematosus

Deficiency of mannose binding lectin (MBL), a C-type lectin with structural similarities to C1q, has been shown to predispose to the development of systemic lupus erythematosus (SLE). Some patients have low serum MBL levels which cannot be explained by either structural gene mutations or promoter polymorphisms. The objective of this study was to detect the presence of autoantibodies against MBL and to evaluate their relationship to serum MBL levels. Anti-MBL antibodies of IgM and IgG classes from consecutive SLE patients (n 1/4 135) and healthy subjects (n 1/4 50) were measured by an in-house ELISA. Using the 90th percentile of controls as a cutoff, more SLE patients [23.7% (32/135)] were found to have IgG anti-MBL antibodies than normal controls [10.0% (5/50)] (P 1/4 0.04). The same trend was observed when ethnicity was taken into account by analysing Caucasians alone (n 1/4 90). IgM anti-MBL antibodies were only found in two SLE patients (2/22, 9.1%) who had no concomitant IgG anti-MBL antibodies. Serum levels of IgG anti-MBL antibodies were found to correlate with serum MBL levels (r 1/4 0.55, P 1/4 0.049). However, the levels of anti-MBL antibodies did not correlate with overall disease activity. Thus the production of anti-MBL antibodies is likely to be a specific antigen-driven process. Its role in lupus pathogenesis remains to be elucidated.

Mannose-binding lectin polymorphisms and rheumatoid arthritis: A short review and meta-analysis

Mannose-binding lectin (MBL) is a pattern recognition receptor of the lectin pathway of complement system. MBL binds to carbohydrates on microorganism's surfaces leading to complement activation, opsonization and phagocytosis. Polymorphisms in the MBL gene (MBL2) are associated with variations on MBL serum levels and with the susceptibility to various infectious and autoimmune diseases. The involvement of the lectin pathway in rheumatoid arthritis (RA) has been demonstrated by several studies and although MBL has been considered to have a dual role in the pathogenesis of the disease, the association between MBL and RA remains inconclusive. In an attempt to clarify this relationship, we developed this short review summarizing accumulated evidences in regard to MBL and RA and a meta-analysis to evaluate the influence of MBL2 polymorphisms on the susceptibility to RA. Among a total of 217 articles that were identified following a predefined search strategy on PubMed, Scopus, Scielo, EMBASE and Cochrane databases, only 13 met all inclusion criteria and were included in the meta-analysis. Data assessment was conducted by three independent investigators and presented in odds ratio (OR) and 95% confidence intervals (CIs) using forest plot charts. Both heterogeneity and publication bias were analyzed. The results of the meta-analysis evidenced that MBL2 low producing OO and XX genotypes do not confer higher risk to RA, even when data were analyzed according to cohort's ethnicity. Further studies are needed in order to clarify the importance of other genes of the lectin pathway in the pathogenesis of RA.

Meta-analysis of functional MBL polymorphisms. Associations with rheumatoid arthritis and primary Sjögren's syndrome

OBJECTIVE

The aim of this study was to determine whether functional mannose-binding lectin gene (MBL) polymorphisms are associated with the susceptibility to rheumatoid arthritis (RA) or primary Sjögren's syndrome (pSS).

METHODS

A meta-analysis was conducted to investigate the potential association of RA or pSS with MBL polymorphisms, including the codon 54 (allele B), codon 57 (allele C), and codon 52 (allele D) variants of exon 1, and the - 550 (allele L) and - 221 (allele X) promoter variants.

RESULTS

A total of 12 comparative studies, including eight RA (1623 patients and 1671 controls) and four pSS (280 patients and 516 controls) studies, were included in the meta-analysis. The meta-analysis revealed no association between the MBL B allele and RA in the overall study population (odds ratio [OR] 0.991, 95 % confidence interval [CI] 0.726-1.355, p = 0.957). However, the meta-analysis showed significant associations between the MBL D, H, and X alleles and RA in the overall population (OR 1.708, 95 % CI 1.077-2.707, p = 0.023; OR 1.936, 95 % CI 1.218-3.078, p = 0.005; OR 1.582, 95 % CI 1.216-2.057, p = 0.001, respectively). An association was found between the MBL B allele and pSS in the overall study population (OR 0.691, 95 % CI 0.541-0.917, p = 0.010). Stratification by ethnicity indicated a trend toward an association between the B allele and pSS in European populations, but no association in Asian populations (OR 0.689, 95 % CI 0.465-1.021, p = 0.063; OR 0.896, 95 % CI 0.311-2.562, p = 0.838, respectively).

CONCLUSION

This meta-analysis demonstrated an association between the MBL D, L, and X alleles and the risk of RA. It also demonstrated an association between the MBL B allele and the susceptibility to pSS, suggesting a protective role of the MBL B allele against the development of pSS.

Elevated Serum Mannose-Binding Lectin Levels Are Associated with Poor Outcome After Acute Ischemic Stroke in Patients with Type 2 Diabetes

The activation of the complement system may be involved in the pathology of stroke and type 2 diabetes (T2DM). We therefore evaluated the long-term prognostic value of early measurement of serum mannose-binding lectin (MBL) levels, an activator of the complement system, in Chinese T2DM with acute ischemic stroke (AIS). Serum MBL levels were determined in T2DM patients with AIS (N = 188). The adjudicated end points were 1-year functional outcomes and mortality. The prognostic value of MBL was compared with the National Institutes of Health Stroke Scale score and with other known outcome predictors. Patients with an unfavorable outcomes and nonsurvivors had significantly increased MBL levels on admission (P < 0.0001 and P < 0.0001). Multivariate logistic regression analysis adjusted for common risk factors showed that MBL was an independent predictor of functional outcome (odds ratio (OR) = 8.99, 95% CI 2.21-30.12) and mortality (OR = 13.22, 95% CI 2.05-41.21). The area under the receiver operating characteristic curve of MBL was 0.75 (95% CI 0.68-0.83) for functional outcome and 0.85 (95% CI 0.80-0.90) for mortality. In type 2 diabetic patients with stroke, high levels of MBL predict future functional outcomes and mortality. This indicated that the elevated MBL levels may play a significant role in the pathology of the subsequent damage and that the pathways leading to complement activation warrant further exploration as potential therapeutic targets to improve the prognosis for these patients.

Elevated plasma CL-K1 level is associated with a risk of developing disseminated intravascular coagulation (DIC)

Collectin kidney 1 (CL-K1) is a recently identified collectin that is synthesized in most organs and circulates in blood. CL-K1 is an innate immune molecule that may play a significant role in host defense. As some collectins also play a role in coagulation, we hypothesized that an effect of CL-K1 may be apparent in disseminated intravascular coagulation (DIC), a gross derangement of the coagulation system that occurs in the setting of profound activation of the innate immune system. DIC is a grave medical condition with a high incidence of multiple organ failure and high mortality and yet there are no reliable biomarkers or risk factors. In our present study, we measured plasma CL-K1 concentration in a total of 659 specimens, including 549 DIC patients, 82 non-DIC patients and 27 healthy volunteers. The median plasma CL-K1 levels in these cohorts were 424, 238 and 245 ng/ml, respectively, with no significant difference in the latter two groups. The incidence of elevated plasma CL-K1 was significantly higher in the DIC patients compared to the non-DIC patients, resulting in an odds ratio of 1.929 (confidence interval 1.041-3.866). Infection, renal diseases, respiratory diseases, and cardiac diseases were more frequently observed in the DIC group than in the non-DIC group. In the DIC group, vascular diseases were associated with elevated plasma CL-K1 levels while age and acute illness had little effect on plasma CL-K1 levels. Independent of DIC, elevated plasma CL-K1 levels were associated with respiratory disease and coagulation disorders. These results suggest that specific diseases may affect CL-K1 synthesis in an organ dependent manner and that elevated plasma CL-K1 levels are associated with the presence of DIC. Further investigations in cohorts of patients are warranted. We propose that elevated plasma CL-K1 may be a new useful risk factor and possibly biomarker for the prediction of developing DIC.

Mannose binding lectin and susceptibility to rheumatoid arthritis in Brazilian patients and their relatives

Introduction

Rheumatoid arthritis (RA) is a commonly occurring systemic inflammatory auto immune disease and is believed to be associated with genetic factors. The innate immune complement protein Mannose binding lectin (MBL) and their MBL2 genetic variants are associated with different infectious and autoimmune diseases.

Methods

In a Brazilian cohort, we aim to associate the functional role of circulating MBL serum levels and MBL2 variants in clinically classified patients (n = 196) with rheumatoid arthritis including their relatives (n = 200) and ethnicity matched healthy controls (n = 200). MBL serum levels were measured by ELISA and functional MBL2 variants were genotyped by direct sequencing.

Results

The exon1+54 MBL2*B variant was significantly associated with an increased risk and the reconstructed haplotype MBL2*LYPB was associated with RA susceptibility. Circulating serum MBL levels were observed significantly lower in RA patients compared to their relatives and controls. No significant contribution of MBL levels were observed with respect to functional class, age at disease onset, disease duration and/or other clinical parameters such as nodules, secondary Sjögren syndrome, anti-CCP and rheumatoid factor. Differential distribution of serum MBL levels with functional MBL2 variants was observed in respective RA patients and their relatives.

Conclusions

Our results suggest MBL levels as a possible marker for RA susceptibility in a Brazilian population.

Association of MASP-2 levels and MASP2 gene polymorphisms with rheumatoid arthritis in patients and their relatives

Background

Mannan-binding lectin-associated serine protease 2 (MASP-2) is a key protein of the lectin pathway of complement. MASP-2 levels have been associated with different polymorphisms within MASP2 gene as well as with the risk for inflammatory disorders and infections. Despite its clinical importance, MASP-2 remains poorly investigated in rheumatoid arthritis (RA).

Methods

In this case-control study, we measured MASP-2 serum levels in 156 RA patients, 44 patient relatives, and 100 controls from Southern Brazil, associating the results with nine MASP2 polymorphisms in all patients, 111 relatives, and 230 controls genotyped with multiplex SSP-PCR.

Results

MASP-2 levels were lower in patients than in controls and relatives (medians 181 vs. 340 or 285 ng/ml, respectively, P<0.0001). Conversely, high MASP-2 levels were associated with lower susceptibility to RA and to articular symptoms independently of age, gender, ethnicity, smoking habit, anti-CCP and rheumatoid factor positivity (OR = 0.05 [95%CI = 0.019–0.13], P<0.0001 between patients and controls; OR = 0.12, [95%CI = 0.03–0.45], P = 0.002 between patients and relatives; OR = 0.06, [95%CI = 0.004–0.73], P = 0.03 between relatives with and without articular symptoms). MASP2 haplotypes *2A1 and *2B1-i were associated with increased susceptibility to RA (OR = 3.32 [95%CI = 1.48–7.45], P = 0.004). Deficiency-causing p.120G and p.439H substitutions were associated with five times increased susceptibility to articular symptoms in relatives (OR = 5.13 [95%CI = 1.36–20.84], P = 0.02). There was no association of MASP-2 levels or MASP2 polymorphisms with autoantibodies, Sjögren's syndrome, nodules and functional class.

Conclusions

In this study, we found the first evidence that MASP-2 deficiency might play an important role in the development of RA and articular symptoms among relatives of RA patients.

Association of MIF-173G/C and MBL2 codon 54 gene polymorphisms with rheumatoid arthritis: a meta-analysis

The aim of this study was to evaluate the association between macrophage migration inhibitory factor (MIF) -173G/C (rs755622), mannose-binding lectin (MBL2) exon 1 codon 54 (rs1800450) gene polymorphisms and rheumatoid arthritis (RA) susceptibility in ethnically different populations. A meta-analysis was conducted (allelic contrast, the additive model, the dominant model and the recessive model) on the MIF-173G/C polymorphism across five studies (four European and one Asian studies), and the MBL2 codon 54 polymorphism with five studies (four Asian and one European studies), respectively. Meta-analysis indicated an association between the MIF-173G/C in all study subjects in allelic contrast (OR=1.19, 95%CI: 1.05-1.35, P=0.001), the additive model (OR=1.68, 95CI: 1.13-2.49, P=0.001), the dominant model (OR=1.17, 95CI: 1.01-1.35, P=0.003), the recessive model (OR=1.63, 95CI: 1.10-2.42, P=0.001). While stratified by ethnicity with European populations, an association was found in allelic contrast (OR=1.20, 95CI: 1.04-1.38, P=0.002), the additive model (OR=1.85, 95CI: 1.19-2.88, P=0.001), the dominant model (OR=1.20, 95CI: 1.02-1.41, P=0.003). With respect to MBL2 codon 54 polymorphism and RA, no association was found in all study subjects in all comparisons, but there was an association while stratified by ethnicity with Asian populations in the dominant model (OR=1.50, 95CI: 1.01-2.23, P=0.007). In conclusion, the present study suggests that the MIF-173G/C polymorphism is associated with RA susceptibility, but the MBL2 codon 54 polymorphism is not associated with RA.

Relevance of the lectin pathway of complement in rheumatic diseases

Due to its importance both in the clearance of pathogens that contribute as rheumatic etiological agents and in the disposal of apoptotic bodies and potential autoimmune initiators, deficiencies of the components of the lectin pathway of complement have been found to increase susceptibility and modulate the severity of most rheumatic disorders. This chapter introduces the general aspects of the structure, function, and genetics of lectin pathway components and summarizes current knowledge of the field regarding rheumatic diseases predisposition and modulation.

Mannose binding lectin and macrophage migration inhibitory factor gene polymorphisms in Turkish children with cardiomyopathy: no association with MBL2 codon 54 A/B genotype, but an association between MIF -173 CC genotype

Myocardial inflammation is one of the commonest mechanisms in cardiomyopathy (CMP). Mannose binding lectin (MBL) is a key molecule in innate immunity, while macrophage migration inhibitory factor (MIF) is a constitutive element of the host defenses. We investigated the possible association between polymorphisms of MBL2 and MIF genes and CMP in Turkish children. Twenty-children with CMP and 30 healthy controls were analyzed for codon 54 A/B polymorphism in MBL, and -173 G/C polymorphism in MIF genes by using PCR-RFLP methods. No significant difference was found between genotypes and alleles of MBL2 gene codon 54 A/B polymorphism in patients and controls (p>0.05). However, serum uric acid levels was found higher in dilated CMP patients with AA genotype. Frequency of MIF -173 CC genotype was significantly higher in patients (p<0.05), and sodium levels were higher in patients with MIF -173 CC genotype. This study is the first to investigate the MBL and MIF gene polymorphisms in Turkish children with CMP. We conclude that CC genotype of MIF (-173) polymorphism may be a risk factor for CMP patients. However, further studies with larger samples are needed to address the exact role of this polymorphism in CMP.

Mannose-binding lectin gene polymorphisms in Brazilian patients with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a disease with unknown etiology but it is probably multifactorial. RA susceptibility is related to genetic, hormonal, immunologic, and environmental factors. Mannose-binding lectin (MBL) is an important protein of the human innate immune system, encoded by the MBL2 gene. Polymorphisms in MBL2 were associated with several diseases, and may be an important factor in RA susceptibility. We analyzed 3 MBL2 gene polymorphisms in 322 Brazilian patients with RA and 345 ethnically matched healthy controls.

METHODS

MBL2 gene variants were analyzed through polymerase chain reaction sequencing.

RESULTS

Considering MBL2 B, C, and D alleles separately, a significant difference in both genotypic and allelic frequencies, particularly concerning frequency of the C allele, was observed comparing European-derived and African-derived individuals (European-derived patients 0.022 vs African-derived patients 0.205; European-derived controls 0.029 vs African-derived controls 0.144; both p < 0.001). We also analyzed MBL2 genotype in relation to extraarticular manifestations. Considering MBL2 variants together, we found an increased frequency of the OO genotype among patients with rheumatoid nodules (p = 0.031), although this association lost significance after Bonferroni correction.

CONCLUSION

Our findings suggest an association of MBL2 genotypes with some clinical manifestations of RA, but more studies are needed to clarify the actual role of MBL in RA.

Mannan Binding Lectin (MBL) genotypes coding for high MBL serum levels are associated with rheumatoid factor negative rheumatoid arthritis in never smokers

Introduction

Previous studies have provided inconsistent results on whether variants in the MBL2 gene, coding for the complement-activating mannan-binding lectin (MBL) protein, associate with rheumatoid arthritis (RA). We re-evaluated this in context of the main environmental and genetic risk factors (smoking, HLA-DRB1 'shared epitope' (SE), PTPN22*620W), which predispose to rheumatoid factor (RF) and/or anti-citrullinated-protein antibody (ACPA)-positive RA.

Methods

In this population-based EIRA study, rheumatoid factor (RF), ACPA, smoking, SE and PTPN22*620W status was determined in incident RA cases and matched controls. MBL-high (n = 1330) and MBL-low (n = 1257) genotypes predicting MBL levels were constructed from four promoter and exon-1 polymorphisms in the MBL2 gene. Odds ratios with 95% confidence interval (OR, 95% CI) were calculated by logistic regression. In extended families (n = 316), previously reported data were re-analyzed, considering RF and smoking.

Results

MBL-high genotypes tended to be associated with RF-negative (OR = 1.20, 95% CI 0.96-1.51) but not RF-positive (OR = 1.00, 95% CI 0.83-1.20) RA. Results divided by ACPA status did not differ. When stratified for smoking, MBL-high genotype was strongly associated with RF-negative RA in never smokers (OR = 1.82, 95% CI 1.24-2.69) but not in ever smokers (OR = 0.96, 95% CI 0.73-1.30). In never smokers, the association was observed in both the RF-negative/ACPA-negative (OR = 1.67, 95% CI 1.10-2.55) and RF-negative/ACPA-positive subgroups (OR = 3.07, 95% CI 1.37-6.89), and remained on an SE/PTPN22*620W negative background. In the extended families, the reported association between high MBL and RA was in fact confined to never smokers.

Conclusions

High MBL may predispose to RF-negative RA but only in individuals who have never smoked. This illustrates the importance of phenotypic subgrouping in genetic studies.

Protective molecules and their cognate antibodies: new players in autoimmunity

Impairment of the clearance of apoptotic material seems to contribute to autoantigen exposure, which can initiate or maintain an autoimmune response in predisposed individuals. Complement component C1q, Creactive protein (CRP), serum amyloid P (SAP), mannose-binding lectin (MBL), apolipoprotein A-1 (Apo A-1) and long pentraxin 3 (PTX3) are molecules involved in the removal of apoptotic bodies and pathogens, and in other antiinflammatory pathways. For this reason they have been called "protective" molecules. C1q has a key role in the activation of the complement cascade and acts as a bridging molecule between apoptotic bodies and macrophages favouring phagocytosis. In addition to other functions, CRP, SAP and MBL bind to the surface of numerous pathogens as well as cellular debris and activate the complement cascade, thus stimulating their clearance by immune cells. The role of PTX3 is more controversial. In fact, PTX also promotes the clearance of microorganisms, but the activation of the complement cascade through C1q and removal of apoptotic material can be either stimulated or inhibited by this molecule. Antibodies against protective molecules have been recently reported in systemic lupus erythematosus and other autoimmune rheumatic diseases. Some of them seem to be pathogenetic and others protective. Thus, protective molecules and their cognate antibodies may constitute a regulatory network involved in autoimmunity. Dysregulation of this system might contribute to the development of autoimmune diseases in predisposed individuals.

Mannose-binding lectin gene (MBL-2) polymorphism in oral lichen planus

TNF-α may be associated with the etiopathogenesis of oral lichen planus (OLP), and it has been suggested that polymorphism of mannose-binding lectin (MBL) increases the in vitro production of TNF- α. The aim of the present study was to assess the relevance of genetic diversity of MBL in OLP. The study sample comprised 90 individuals, 45 OLP patients and 45 healthy volunteers. MBL-2 gene was amplified using real-time PCR. Frequency of A/A genotype was 55.6% in OLP and 53.3% in healthy volunteers. Likewise, A/0 heterozygote genotype was found in 42.2% and 35.6%; 2.2% and 11.1%, had the recessive 0/0 genotype respectively. Frequencies of the "A" and "0" alleles were 77% and 23% in the OLP group and 71.2% in control group. There were no statistically significant differences regarding genotype frequency (p = 0.546) or allele frequency (p = 0.497). In conclusion, no significant association was found between polymorphism of MBL-2 gene and OLP.

Mannose-binding lectin polymorphisms and recurrent respiratory tract infection in Chinese children

In order to establish the reference value of mannose-binding lectin (MBL) serum level in children and to investigate the correlation between the polymorphisms of MBL2 gene and serum MBL level in healthy Chinese of Han ethnic group and in children of Chinese Han ethnic group with recurrent respiratory tract infections (RRTI), the concentration of oligomerized MBL was measured by enzyme-linked immunosorbent assay, and MBL2 gene polymorphisms were analyzed by restriction fragment length polymorphism of polymerase chain reaction and polymerase chain reaction-sequence specific primer. The median MBL levels in the 470 normal children were 2536 ng/ml, and the P(2.5)-P(97.5) was 161-5,070 ng/ml. Our research showed that two promoter polymorphisms at -550, -221 of start codon and coding variants at codon 54 of MBL2 gene affected the protein level significantly and the most frequent genotype in Hans is HYPA/HYPA. Our results also showed that serum MBL level was significantly lower in recurrent respiratory tract infections patients compared with healthy controls (Z, -3.04, P = 0.002). The frequency of the promoter LXP haplotype and the B allele was significantly higher in RRTI patients than in controls (chi (2) 4.05, P < 0.05; OR 1.63, 95%CI 1.01 approximately 2.62; chi (2) 4.27, P < 0.05; OR 1.94, 95%CI 1.02 approximately 3.68).

CONCLUSION

We have established that the reference value of serum MBL level in Chinese aged between 0 and 6 years (161-5,070 ng/ml), and we found that LXP and the B are risk factors for RRTI.

Mannose-binding lectin polymorphisms are not associated with rheumatoid arthritis--confirmation in two large cohorts

OBJECTIVES

In RA, conflicting results have been described on the association between genotypes of the complement factor mannose-binding lectin (MBL) and disease susceptibility and severity. This might be due to underpowerment of previous research work and the fact that no confirmation cohorts were used. Therefore a different approach is warranted.

METHODS

MBL2 gene polymorphisms were determined in two RA cohorts (378 and 261 cases) and 648 controls. Considering MBL polymorphisms, cases and controls were categorized in groups of high, intermediate and low MBL production. The total sample size allows detection of a potential association between RA susceptibility and MBL groups with an odds ratio of 1.37 (alpha < 0.05; 1-beta > 0.8). Disease severity as defined by the need for anti-TNF therapy was also analysed for possible associations with MBL groups.

RESULTS

There was no difference in the frequencies between MBL genotypes of RA cases and controls that are associated with high (cases 54.4%, controls 57.0%), intermediate (cases 28.9%, controls 27.5%) or low (cases 16.7%, controls 15.5%) MBL production. Furthermore, there was no association between MBL groups and disease severity.

CONCLUSIONS

MBL genotype groups are not associated with RA disease susceptibility or severity in this large study including a confirmation cohort. Compared with previous smaller studies these results add to more definite conclusions.

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.

Lack of association between mannose-binding lectin gene polymorphisms and juvenile idiopathic arthritis in a Han population from the Hubei province of China

Many studies have reported that polymorphisms of the mannose-binding lectin (MBL) gene are associated with autoimmune disease. Here, we investigate the relationship between MBL gene polymorphisms and susceptibility to juvenile idiopathic arthritis (JIA) in a Han-nationality population from the Hubei province of China. PCR-restriction fragment length polymorphism was used to investigate polymorphisms of codons 54 and 57 in exon 1 of the MBL gene in 93 patients with JIA and 48 control children. Neither group showed codon 57 polymorphisms. There was no significant difference in the genotypic frequencies of codon 54 between patients with JIA and healthy controls (wild type, 71.0% versus 75.0%, respectively; heterozygous type, 25.8% versus 25.0%, respectively; and homozygous type, 3.2% versus 0.0%, respectively). In addition, no association was found between the subgroups of patients with JIA and control individuals. Our results provide no evidence for a relationship between MBL gene mutation and susceptibility to JIA.

Genetic association study between mbl2 and asthma phenotypes in Chinese children

Mannose-binding lectin (MBL), a member of the innate immune system, initiates complement deposition on microbial surfaces. MBL deficiency is associated with severe respiratory infections. Polymorphisms in the MBL gene (mbl2) were associated with the susceptibility and severity of autoimmune diseases. This study investigated whether mbl2 polymorphisms at positions -550 and -221 and at codon-54 are associated with asthma phenotypes in Chinese children. Asthmatics aged 5-18 yr and non-allergic controls were eligible, and their plasma total and allergen-specific immunoglobulin E (IgE) concentrations were measured by micro-particle immunoassay and fluorescent enzyme immunoassay. mbl2 polymorphisms were genotyped by restriction fragment length polymorphism. Three hundred and seventeen asthmatic children and 140 controls were recruited, with their mean (s.d.) log-transformed plasma total IgE being 2.61 (0.61) and 1.77 (0.77), respectively (p < 0.0001). Polymorphisms at -550 and codon-54 (p < 0.0001 for both) but not at -221 (p = 0.534) of mbl2 were significantly associated with plasma MBL concentrations. mbl2 genotypes were not associated with asthma, atopy, sensitization to individual aeroallergens or spirometric variable. Subjects with LYB haplotype had the lowest plasma MBL concentrations (p < 0.0001), but two- and three-loci mbl2 haplotypes were also not associated with asthma diagnosis. However, patients with LY and LYB haplotypes were less likely to be atopic (p = 0.006 and 0.031). Subjects with LY and LYA were also less likely to be sensitized to cockroach (p = 0.035 and 0.047). The latter three associations became insignificant when adjusted for multiple comparisons. Despite the importance of MBL in innate immunity, our mbl2 polymorphisms only show weak association with asthma and atopy in children.

Mannose-Binding Lectin: Clinical Implications for Infection, Transplantation, and Autoimmunity

Mannose-binding lectin (MBL) is a recognition molecule of the lectin pathway of complement and a key component of innate immunity. MBL variant alleles have been described in the coding region of the MBL gene, which are associated with low MBL serum concentration and impaired MBL structure and function. Both high and low serum levels of functional MBL have been associated with a variety of diseases and disease complications. Functioning as double-edged sword, low MBL serum levels have been shown to enhance the risk for infections. On the other hand, high MBL serum levels and high MBL activity have been associated with inflammatory diseases, transplant rejection, and diabetic nephropathy. Underscoring the Jekyll-and-Hyde character of MBL, both high and low serum MBL levels are associated with several aspects of autoimmune diseases. This review provides a general outline of the genetic and molecular characteristics of MBL and discusses MBL-disease association and its consequence in infection, transplantation, and autoimmunity.

Autoimmune pancreatitis and complement activation system

OBJECTIVES

Autoimmune pancreatitis is characterized by increased serum level of IgG4, but its pathogenesis has not been fully elucidated. Because this disease is occasionally associated with decreased levels of complements, we sought to clarify which complement activation system was operating in its active state.

METHODS

We measured serum levels of complements, mannose-binding lectin, and circulating immune complex in patients with autoimmune pancreatitis, patients with chronic pancreatitis, and healthy controls.

RESULTS

We found high serum circulating immune complex values, which decreased significantly after corticosteroid therapy. In patients with autoimmune pancreatitis, elevated levels of circulating immune complex, as determined by C1q assay, were significantly associated with increased serum levels of IgG1 and decreased levels of C4, as well as with a tendency toward decreased levels of C3. There were no significant differences in the serum levels of mannose-binding lectin or in the frequency of a mutant allele of mannose-binding lectin between patients with autoimmune pancreatitis and those with chronic calcifying pancreatitis. Furthermore, corticosteroid therapy had no effect on the level of mannose-binding lectin.

CONCLUSIONS

Autoimmune pancreatitis exhibits a high serum circulating immune complex values in its active state, which links to a complement activation system with a classic pathway rather than the mannose-binding lectin pathway or alternative pathways.

Protective Molecules–C-Reactive Protein (CRP), Serum Amyloid P (SAP), Pentraxin3 (PTX3), Mannose-Binding Lectin (MBL), and Apolipoprotein A1 (Apo A1), and Their Autoantibodies: Prevalence and Clinical Significance in Autoimmunity

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.

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.

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.

Role for Innate Immunity in Rheumatoid Arthritis

Innate immunity is the first line of defense against pathogenic microorganisms (bacteria, viruses, fungi, and parasites). After a long period of neglect, innate immunity is again recognized as a key mechanism not only in preventing invasion of the body by microorganisms, but also in contributing to the pathogenesis of autoimmune and inflammatory diseases by deviating the immune response or promoting the emergence of a regulatory response. The many factors involved in innate immunity often act in parallel or in alternation to generate adaptive immune responses. Innate immune responses are specific for groups of molecules or macromolecules found in components of microorganisms, usually the cell wall. The cellular and protein effectors of innate immunity are found in the rheumatoid synovium, and an increasing body of evidence indicates that they are directly involved in joint inflammation and in destruction of the joint cartilage and bone. In addition, they may have regulatory effects on inflammation and immunity. Whether innate immune mechanisms are causes or consequences of inflammation, and whether they regulate or amplify adaptive immune responses, they constitute a target of choice for new antiinflammatory and immunoregulating treatment strategies.

Modulating effects of mannose binding lectin genotype on arterial stiffness in children after Kawasaki disease

Systemic arterial stiffness is increased in patients after Kawasaki disease (KD). Recently, associations between mannose-binding lectin (MBL) gene mutation and coronary complications in infants with KD and atherosclerosis in adults have been reported. We tested the hypothesis that MBL genotype modulates arterial stiffness in children after KD. Seventy-one KD patients (42 with and 29 without coronary aneurysms), aged 9.5 +/- 3.7 y, and 41 age-matched controls were studied. We determined and compared their blood pressure, brachioradial arterial stiffness as determined by pulse wave velocity (PWV), fasting total cholesterol, serum MBL level, and MBL genotype. Additionally, the modulating effects of different MBL expression genotypes [high level (HL) versus intermediate or low level (IL/LL)] on arterial stiffness in different groups were assessed. The MBL genotype distributions did not differ between patients and controls (p = 0.41) or between patients with and without coronary aneurysms (p = 0.42). Patients with IL/LL expression genotypes had significantly faster PWV than those with HL expression genotypes (7.93 +/- 1.38 m/s versus 6.67 +/- 2.28 m/s, p = 0.027). This genotype-modulating effect is more pronounced in patients without (HL 8.86 +/- 0.77 m/s versus IL/LL 6.48 +/- 2.32 m/s, p = 0.02) than those with (HL 7.50 +/- 1.41 m/s versus IL/LL 6.80 +/- 2.28 m/s, p = 0.32) coronary aneurysms. Multiple linear regression analysis identified age (beta = 0.26, p = 0.012), being a Kawasaki patient (beta = 0.22, p = 0.015), and MBL IL/LL genotype subgroup (beta = 0.20, p = 0.03) as significant determinants of arterial stiffness in the entire cohort. In conclusion, MBL genotype modulates arterial stiffness, an important cardiovascular risk factor, in children after KD.

The potential role of mannan-binding lectin in the clearance of self-components including immune complexes

Mannan-binding lectin (MBL) is a pattern recognition receptor in the innate immune system. It recognizes certain sugar residues arranged in a pattern that enables MBL to bind with sufficient strength. Such sugar patterns are common on the surface of many microorganisms, and MBL has therefore been considered to be an agent that can discriminate between self and nonself. There is, however, increasing evidence supporting that MBL, like many membrane-bound C-type lectin-like receptors, also helps to dispose of various outworn or abnormal body components. Most self-components are protected with sialic acid or galactose that disrupt the pattern of the sugars that MBL can bind, but MBL may be significantly involved in the elimination of self-components that have lost these protective terminal residues. The role of MBL in the clearance of invading pathogens has previously been thoroughly reviewed. Here, we review some findings that support the notion that MBL may contribute to noninflammatory removal of immune complexes and abnormal cells by the reticuloendothelial system. Defects in this clearance mechanism may cause an accumulation of potentially dangerous self-components, thereby increasing the likelihood of chronic inflammation and autoimmunity.

The natural history and prognosis of rheumatoid arthritis: association of radiographic outcome with process variables, joint motion and immune proteins

OBJECTIVE

The purposes of the present study were: 1) to investigate how the long-term course of outcome and inflammatory variables could be described in individual patients and suitably summarized in groups of patients; 2) to investigate the associations between outcome and inflammatory variables on the basis of the defined summary measures; and 3) to investigate new prognostic aspects of RA by means of frozen sera and DNA specimens.

PATIENTS AND METHODS

During the period 1966-78, 685 Danish Caucasian patients with RA, classified according to the 1958 American Rheumatism Association (ARA) criteria, were admitted to the Department of Rheumatology of Aarhus University Hospital. For scientific purposes all patients went through the same examination programme, including biochemical variables, clinical evaluation of 68 diarthrodial joints, and radiographic evaluation of 46 diarthrodial joints. Since 1987, data from these patients have been organized in a database. The data are arranged according to onset of disease. This thesis is based on about 600,000 data-points from 257 patients.

RESULTS

The thesis is based on six studies. The first study shows that early symptomatic improvement of RA during gold treatment was stable over several years, but when evaluated radiographically, the condition continued to deteriorate. In the second study, six main types of radiographic progression were identified: (a) a rare type with no radiographic progression at all (<1%); (b) a type with a slow or moderate onset, but an increasing progression rate (exponential growth type) (9%); (c) a linear type (30%); (d) a type with a moderate to fast onset, and a stable progression rate (the square root type) (11%); (e) a type with a fast onset, but a later decreasing progression rate (the first order kinetics type) (30%) and (f) a type characterized by slow onset, then acceleration and later deceleration (the sigmoid type) (20%). The fact that there was a systematic progression was used to define a system of radiographic events, which could be used as outcome measures in prediction models of the long-term course of RA. The third study shows that low serum levels of the complement-activating serum lectin, mannan (mannose) binding protein (lectin) (MBP = MBL), are associated with a higher erythrocyte sedimentation rate (ESR) (p=0.006), joint swelling score (JS score) (p=0.019), limitation of joint motion score (LM score) (p=0.027), and annual increase in radiographic destruction score (R score) (p=0.053). The fourth study demonstrated a highly significant association between summary measures of inflammatory variables and radiographic outcome, as defined in the second study, indicating that the degree of inflammation is important for the development of destructive joint damage in RA. The fifth study showed that MBL-insufficient patients (two defective structural MBL alleles, or one defective allele combined with a low-expression variant of the normal allele) had a relative risk of a severe radiographic event of 3.1 compared with the MBL competent group (p<0.0001). The sixth study showed that the relative risk (RR) of early interleukin (IL)-1alpha auto-antibodies (aAb) positive patients developing serious radiographic joint destruction was significantly lower than for IL-1alpha aAb-negative patients, RR=0.29 (p=0.04). In rheumatoid factor (RF) positive patients RR was only 0.18 (p=0.02). Patients who seroconverted >2 years after the onset of RA showed the most aggressive development of joint erosion, with RR of serious radiographic joint destruction of 2.56 (p=0.048). Other factors investigated in subgroups of the patients were HLA-DR4, chemokine receptor 5 (CCR 5) genotypes. IL-6 aAb, vascular endothelial growth factor (VEGF) aAb, and interferon (IFN)-gamma aAb. About 80% of the patients were HLA-DR4 positive, indicating the importance of HLA-DR4 as a predisposing factor for RA. There was no association between IL-6 aAb and radiographic outcome, or CCR5 genotypes and radiographic outcome. VEGF aAb and IFN-gamma aAb were quantitatively unimportant.

CONCLUSION

In spite of a general improvement in single measures of inflammatory variables, and a general deterioration in radiographic outcome of RA, there is a highly significant association between summary measures of inflammatory variables and radiographic outcome. The progression of radiographic damage in RA follows mathematical patterns. A new method of evaluating the long-term radiographic outcome by means of Kaplan-Meier plots is demonstrated. It is shown that MBL and IL-1alpha aAb are predictors of the prognosis of RA and may play important roles in the pathogenesis of RA.

Serum mannose-binding lectin levels and mbl2 gene polymorphisms in different age and gender groups of southern Chinese adults

Mannose-binding lectin (MBL) is an acute-phase serum protein, and its inherited deficiency has been shown to predispose to infections. The developmental profile of serum MBL in preterm infants has been demonstrated previously. To determine the profiles of serum MBL levels and mbl2 polymorphisms over age and genders in an adult population, samples from 689 southern Chinese (age range 16-57 years; 382 males and 307 females) were studied using enzyme-linked immunosorbent assay and high-throughput genotyping of mbl2. Serum MBL levels maintained within a narrow range from age groups of 16-20 years old to 31-40 years old (mean of 2050-2160 micro g/l) and declined to a mean of 1466 micro g/l in the last age group 41-57 years old. No significant differences were found in the distributions of mbl2 haplotypes (YA, XA and YB) among all these age groups. Between gender groups, no significant imbalance of MBL profile in terms of serum MBL levels and distribution of mbl2 haplotypes was found. Results suggest an important role of circulating MBL in first-line host defence because MBL maintains at fairly constant levels after childhood and no gender influence on the MBL profile.

Approaches to identifying genetic predictors of clinical outcome in rheumatoid arthritis

Predicting which patients with rheumatoid arthritis (RA), at presentation, are likely to suffer a severe disease course based on genotype data would be a major clinical advance. It would ensure that patients at highest risk of a severe outcome could be targeted with early aggressive therapies. With a better understanding of interactions between genotype and drug response it would be possible to prescribe treatments most likely to be efficacious and safe for specific patient subgroups. While a clear genetic component has been demonstrated in RA severity, the identification of genetic factors poses a challenge to researchers in the field. Initiatives such as the SNP Consortium and advances in genotyping technology have facilitated the investigation of genetic factors in both disease susceptibility and severity. However, several other factors, such as the availability of suitable longitudinal cohorts, definition of outcome measures, study design, selection of genetic markers, and statistical power, will all contribute to the likely success of genetic studies. Several strategies that have been applied in the pursuit of genetic predictors of clinical outcome in RA. While some encouraging results have been generated, it has so far been difficult to quantify the predictive value of genetic markers and extrapolate the results from genetic studies to clinic patients. Establishing high quality prospective inception cohorts, a more systemic approach to defining suitable outcome measures, and understanding the effects of treatment, will be critical to the eventual identification of good predictive genetic markers.

Disease-associated mutations in human mannose-binding lectin compromise oligomerization and activity of the final protein

Deficiency of human mannose-binding lectin (MBL) caused by mutations in the coding part of the MBL2 gene is associated with increased risk and severity of infections and autoimmunity. To study the biological consequences of MBL mutations, we expressed wild type MBL and mutated MBL in Chinese hamster ovary cells. The normal MBL cDNA (WT MBL-A) was cloned, and the three known natural and two artificial variants were expressed in Chinese hamster ovary cells. When analyzed, WT MBL-A formed covalently linked higher oligomers with a molecular mass of about 300-450 kDa, corresponding to 12-18 single chains or 4-6 structural units. By contrast, all MBL variants formed a dominant band of about 50 kDa, with increasingly weaker bands at 75, 100, and 125 kDa corresponding to two, three, four, and five chains, respectively. In contrast to WT MBL-A, variant MBL formed noncovalent oligomers containing up to six chains (two structural units). MBL variants bound ligands with a markedly reduced capacity compared with WT MBL-A. Mutations in the collagenous region of human MBL compromise assembly of higher order oligomers, resulting in reduced ligand binding capacity and thus reduced capability to activate complement.

The role of mannose-binding lectin in health and disease

Mannose-binding lectin (MBL) is a pattern recognition molecule of the innate immune system. It belongs to the collectin family of proteins in which lectin (carbohydrate-recognition) domains are found in association with collagenous structures. In man, these proteins include serum MBL, lung surfactant protein A (SP-A) and lung surfactant protein D (SP-D). MBL binds to a range of sugars including N-acetyl-D-glucosamine, mannose, N-acetyl-mannosamine, fucose and glucose. This permits the protein to interact with a wide selection of viruses, bacteria, yeasts, fungi and protozoa decorated with such sugars. Unlike the other collectins, MBL bound to microbial surfaces is able to activate the complement system in an antibody and C1-independent manner. This activation is mediated by complexes of MBL with a serine protease called MBL-associated serine protease 2 (MASP-2), which specifically cleaves C4 and C2 to create a C3 convertase enzyme. MBL may also interact directly with cell surface receptors and thereby promote opsonophagocytosis by a complement-independent pathway. It has been suggested that MBL plays an important role in the first hours/days of any primary immune response to a sugar decorated pathogen. This provides the host with a first-line of defence before the adaptive immune system becomes operative and in humans may be particularly important between 6 and 18 months of age when the adaptive system is still immature. MBL deficiency is one of the most common human immunodeficiencies and arises primarily from three single point mutations in exon 1 of the MBL-2 gene. These mutations result in a failure to assemble fully functional multimeric protein. Several studies have shown that deficiency of MBL increases the overall susceptibility of an individual to infectious disease. The most striking example of this is the association of acute respiratory tract infections with MBL deficiency in early childhood. In contrast, there is evidence that for some intracellular parasites MBL deficiency may be protective and this might explain the high frequency of MBL mutations in sub-Saharan Africa and South America. Increasingly, there is evidence that the association between MBL levels and disease is complex. For example, the protein appears to influence the severity of several diseases. The mechanism whereby MBL exerts such effects is unclear but one possibility is through a dose-dependent modulation of pro-inflammatory cytokines.

Absence of association between mannose-binding lectin gene polymorphisms and HIV-1 infection in a Colombian population

Mannose-binding lectin (MBL) is a calcium-dependent lectin shown to play an important role in innate immunity to infection by activating the classical complement pathway and phagocytosis. In vitro studies have shown that MBL is able to bind to the gp120 HIV-1 surface antigen, and variants of the gene are associated with increased risk of HIV infection among Scandinavians. We investigated the association of genetic MBL variants and HIV-1 infection in 278 Colombian HIV-infected and control individuals. MBL genotype frequencies were similar for both groups, and no association was detected between MBL alleles B, C, and D and susceptibility to HIV-1 infection ( P=1.0). Since there is a well-documented link between the tested MBL alleles and very low MBL serum concentration, these results do not support the hypothesis that MBL levels are a risk factor for HIV-1 infection in Colombia.

Mannose binding lectin (MBL) polymorphisms associated with low MBL production in patients with dermatomyositis

One theory for the pathophysiology of photosensitive autoimmune skin diseases is that photoinduction of tumor necrosis factor alpha (TNFalpha) secretion leads to keratinocyte apoptosis and translocation of previously sequestered cellular antigens that then activate the immune system. We previously found an association of the overproducing TNFalpha-308 A variant with adult dermatomyositis and with subacute cutaneous lupus erythematosus. Here we focused on mannose binding lectin (MBL), which is one of several proteins involved in clearance of apoptotic cells and could thereby lessen photosensitive autoimmunity. We examined three variant MBL polymorphisms associated with decreased MBL protein (Asp54, Glu57, and the LX promoter polymorphism) in adult dermatomyositis, subacute cutaneous lupus erythematosus, and discoid lupus, and controls. The variant Asp54 allele was positively associated with adult dermatomyositis in a dose-responsive fashion (p=0.0004), as was the Glu57 allele (p=0.004). None of the three variant MBL alleles considered individually was significantly associated with either subacute cutaneous lupus erythematosus or discoid lupus. In adult dermatomyositis patients homozygous for the wild-type TNFalpha-308G allele (GG), i.e., presumably without elevated TNFalpha production, 69% had at least two of the MBL polymorphisms, versus 20% of healthy GG controls (p=0.0011). Combinations of low-producing MBL variants were over-represented in adult dermatomyositis in a dose-responsive fashion (p=0.0002). In adult dermatomyositis patients with one variant TNFalpha-308 A allele (GA), 46% had at least two MBL polymorphisms, versus 7% of GA controls (p=0.0077). Thus, low-producing MBL genes are very strongly associated with adult dermatomyositis. Our model is that genetic polymorphisms leading to overproduction of apoptotic keratinocytes and then impaired clearance of these cells contribute to the pathogenesis of adult dermatomyositis, a photoinduced autoimmune skin disease.

Mannan-binding lectin and its role in innate immunity

Mannan-binding lectin (MBL) is a plasma collectin (C-type lectin with a collagen-like domain) and is considered an important component of innate immunity. Circulating MBL is genetically determined for the major part, but plasma concentration is also markedly influenced by nongenetic factors. The carbohydrate-binding ability of MBL can be inhibited by simple sugars like mannose, fucose and N-acetylglucosamine, but its greatest avidity appears to be for repeating mannose-based structural patterns typical of microbial surfaces. By this means, MBL can bind to a wide variety of bacteria and other microbes, neutralizing them and/or opsonizing them by activating complement using the recently discovered lectin pathway of complement activation. Individual humans differ 1000-fold in MBL concentration, and individuals with low circulating MBL appear to be more vulnerable to infections in a number of clinical settings, especially when combined with secondary immune deficiency. The best evidence that MBL deficiency or insufficiency is physiologically relevant comes from a rapidly expanding literature of clinical studies. MBL insufficiency appears to be a significant risk factor for infections in infants, and for individuals of any age undergoing chemotherapy or post-transplant immunosuppression. Moreover, MBL appears to have a significant influence on the course of certain chronic diseases like rheumatoid arthritis and cystic fibrosis. Replacement therapy with a plasma-derived product is safe and seems promising, while recombinant MBL provides hope for large-scale therapeutic applications. Randomized clinical trials of MBL therapy, which are now on the horizon, should provide unambiguous evidence for the physiological significance of MBL in innate immunity.

IL-6 in autoimmune disease and chronic inflammatory proliferative disease

Interleukin 6 (IL-6), which was originally identified as a B-cell differentiation factor, is now known to be a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several disease processes. The expression of constitutively high levels of IL-6 in transgenic mice results in fatal plasmacytosis, which has been implicated in human multiple myeloma. Increased IL-6 levels are also observed in several diseases, including rheumatoid arthritis (RA), systemic-onset juvenile chronic arthritis (JCA), osteoporosis, and psoriasis. IL-6 is critically involved in experimentally induced autoimmune disease, such as antigen-induced arthritis (AIA), and experimental allergic encephalomyelitis. All these clinical data and animal models suggest that IL-6 plays critical roles in the pathogenesis of autoimmune diseases. Here we review the evidence for the involvement of IL-6 in the pathophysiology of autoimmune diseases and chronic inflammatory proliferative diseases (CIPD) and discuss the possible molecular mechanisms of its involvement.