Acute respiratory tract infections and mannose-binding lectin insufficiency during early childhood

Markers of early disease and prognosis in COPD

COPD is a complex disease with multiple pathological components, which we unfortunately tend to ignore when spirometry is used as the only method to evaluate the disorder. Additional measures are needed to allow a more complete and clinically relevant assessment of COPD. The earliest potential risk factors of disease in COPD are variations in the genetic background. Genetic variations are present from conception and can determine lifelong changes in enzyme activities and protein concentrations. In contrast, measurements in blood, sputum, exhaled breath, broncho-alveolar lavage, and lung biopsies may vary substantially over time. This review explores potential markers of early disease and prognosis in COPD by examining genetic markers in the α₁-antitrypsin, cystic fibrosis transmembrane conductance regulator (CFTR), and MBL-2 genes, and by examining the biochemical markers fibrinogen and C-reactive protein (CRP), which correlate with degree of pulmonary inflammation during stable conditions of COPD. Chronic lung inflammation appears to contribute to the pathogenesis of COPD, and markers of this process have promising predictive value in COPD. To implement markers for COPD in clinical practice, besides those already established for the α₁-antitrypsin gene, further research and validation studies are needed.

Pathway-specific complement activity in pigs evaluated with a human functional complement assay

BACKGROUND

The complement system is an important part of innate immunity. Complement deficiencies or inappropriate activation of complement may cause severe diseases. The complement functional test, Wielisa, assesses all three complement activation pathways in humans. It is important to have assays available to determine the functional complement activity in research animals. Since the pig is a relevant animal in experimental research, the aim of the present study was to evaluate the applicability of this human complement assay in pigs.

METHODS

Normal pig serum was serially diluted and assayed in the Wielisa test which is based on the activation of complement detected with an antibody against activated C9. The specificity of the three pathways was assessed using purified human MBL and mouse monoclonal antibodies against human C1q and pig factor D. Sera from 103 pigs and 38 newborn pigs were analyzed. Finally, functional activity of all pathways was assessed in vitro and in vivo in the absence and presence of complement inhibitors.

RESULTS

The detection antibody showed cross-reactivity against pig. Normal pig serum showed activity in all pathways however about 10-fold more serum was required to obtain values comparable to human serum. Anti-human C1q and anti-pig factor D antibodies abolished classical and alternative pathway activity, respectively. Sera with low lectin pathway activity reconstituted with purified human MBL, fully recovered this activity. No deficiencies were found in classical or alternative pathway, whereas the lectin pathway showed reduced activity in a substantial number of pigs, similar to the situation in humans. Finally, the assay was successfully used to evaluate and monitor inhibition of pig complement in vitro and in vivo.

CONCLUSIONS

The human complement Wielisa test can be used for functional evaluation of all complement pathways in pig serum.

Properdin deficiency associated with recurrent otitis media and pneumonia, and identification of male carrier with Klinefelter syndrome

Properdin is an initiator and stabilizer of the alternative complement activation pathway (AP). Deficiency of properdin is a rare X-linked condition characterized by increased susceptibility to infection with Neisseria meningitidis associated with a high mortality rate. We report properdin deficiency in a large Pakistani family. The index cases were found by screening for immunodeficiency due to a history of recurrent infections. This revealed absent AP activity, but normal classical and lectin pathway activity. Sequencing of the properdin gene (PFC) revealed a novel frameshift mutation. When all available relatives (n=24) were screened for the mutation, four affected males, four female carriers and a male heterozygous carrier were identified. He was subsequently diagnosed with Klinefelter syndrome. A questionnaire revealed a striking association between properdin deficiency and recurrent otitis media (P=0.0012), as well as recurrent pneumonia (P=0.0017). This study is the first to show a significant association between properdin deficiency and recurrent infections.

Mannose-binding lectin deficiency in a child with recurrent infections

We describe an 11 month old girl with mannose-binding lectin deficiency who presented with recurrent infections. Her mother and brother also were affected. Mannose-binding deficiency is common, and we suggest that testing for it should be included in the evaluation of children with increased susceptibility to infection.

A toll-like receptor 4 variant is associated with fatal outcome in children with invasive meningococcal disease

AIMS

Toll-like receptor 4 (TLR4) is the major endotoxin signalling receptor of the innate immune system and is required for efficient recognition of bacterial infections. Here, we analysed a possible association between the TLR4 variant Asp299Gly and disease outcome in children with invasive meningococcal disease.

METHODS

In total, 197 children with invasive meningococcal disease were analysed for the TLR4 Asp299Gly variant. Genotyping results were correlated with mortality, the frequency of ventilation support, application of inotropic substances, skin grafting, and limb loss.

RESULTS

The overall Asp299Gly allele frequency was 9.4%. Detection of a heterozygous Asp299Gly TLR4 mutation was significantly associated with fatal outcome (non-survivor group: 31.6% vs. survivor group: 12.1%; p = 0.021) and was even more pronounced in patients with disease onset less than 24 months of age (non-survivor group: 42.8% vs. survivor group: 10.2%; p = 0.006). In this age group, ventilation support was also more frequent in patients with the Asp299Gly genotype (37.5% vs. 6.2%).

CONCLUSION

Our data suggest that the heterozygous TLR4 Asp299Gly genotype is associated with an increased mortality in children with invasive meningococcal disease.

Exploring the role of polymorphisms in ficolin genes in respiratory tract infections in children

Ficolins are pattern-recognition molecules that appear to be relevant for innate immune defence against infections. The ficolin genes in Caucasians are polymorphic and genetic variations may have functional consequences, both in relation to function and concentration. Low levels of Ficolin-2 have been suggested to associate with recurrent respiratory tract infections (RTI), whereas data on Ficolin-3 are still very limited. We investigated the association between variation in genes encoding Ficolin-2 (FCN2) and Ficolin-3 (FCN3) and frequency of RTI during the first 4 years of life. The study population consisted of 900 children from a large, population-based birth cohort of Dutch children, followed prospectively from birth to 4 years of age. The number of RTI was assessed by annual parental questionnaires. Nine single nucleotide polymorphisms in FCN2 and two in FCN3, all based on functionality or haplotype-tagging characteristics, were determined and haplotypes constructed. We found that single nucleotide polymorphisms in FCN2 and FCN3 were not associated with increased risk of RTI during the first 4 years of life. No difference existed between haplotype-frequencies of FCN2 and FCN3 in children grouped according to the reported number of RTI. In conclusion, at a population level, genetic variation in ficolin genes FCN2 and FCN3 do not seem to contribute to the risk of RTI in Caucasian children.

Genetic and other factors determining mannose-binding lectin levels in American Indians: the Strong Heart Study

Background

Mannose-binding lectin (MBL) forms an integral part of the innate immune system. Persistent, subclinical infections and chronic inflammatory states are hypothesized to contribute to the pathogenesis of atherosclerosis. MBL gene (MBL2) variants with between 12 to 25% allele frequency in Caucasian and other populations, result in markedly reduced expression of functional protein. Prospective epidemiologic studies, including a nested, case-control study from the present population, have demonstrated the ability of MBL2 genotypes to predict complications of atherosclerosis,. The genetic control of MBL2 expression is complex and genetic background effects in specific populations are largely unknown.

Methods

The Strong Heart Study is a longitudinal, cohort study of cardiovascular disease among American Indians. A subset of individuals genotyped for the above mentioned case-control study were selected for analysis of circulating MBL levels by double sandwich ELISA method. Mean MBL levels were compared between genotypic groups and multivariate regression was used to determine other independent factors influencing MBL2 expression.

Results

Our results confirm the effects of variant structural (B, C, and D) and promoter (H and Y) alleles that have been seen in other populations. In addition, MBL levels were found to be positively associated with male gender and hemoglobin A1c levels, but inversely related to triglyceride levels. Correlation was not found between MBL and other markers of inflammation.

Conclusion

New data is presented concerning the effects of known genetic variants on MBL levels in an American Indian population, as well as the relationship of MBL2 expression to clinical and environmental factors, including inflammatory markers.

Surfactant protein A and D gene polymorphisms and protein expression in victims of sudden infant death

AIM

To investigate the innate immune components surfactant protein A (SP-A) and D (SP-D) in victims of sudden infant death syndrome (SIDS).

METHODS

Ten common single nucleotide polymorphisms (SNPs) in the exons of SP-A1, SP-A2 and SP-D genes were analysed in 42 cases of SIDS and 46 explained sudden infant deaths. SP-A and SP-D protein expression in tissue from the aerodigestive tract was semi-quantitatively evaluated by immunohistochemistry.

RESULTS

SP-D immunoreactivity was found in lungs and tissue from submandibular gland, palatine tonsils and duodenum. Positive SP-A immune staining was found exclusively in lung tissue. Neither the allele nor the haplotype distribution of the SP-A and SP-D genes was significantly different in SIDS compared to explained deaths. The most common SP-A haplotype, 6A2/1A0, tended to be overrepresented in the cases with low immunohistochemical SP-A expression (61%) compared to cases with high expression (49%), p = 0.08. The SP-D expression was not influenced by the 11 C/T or 160 A/G polymorphisms.

CONCLUSION

No significant association between the common genetic variants of SP-A and SP-D and SIDS is disclosed by the present study. However, low SP-A protein expression may possibly be determined by the 6A2/1A0 SP-A haplotype, this should be subject for further investigation.

Polymorphisms in the mannan-binding lectin gene are not associated with questionnaire-reported respiratory tract infections in children

BACKGROUND

Low mannan-binding lectin (MBL) levels, caused by MBL2 polymorphisms, are suggested to contribute to susceptibility to respiratory tract infections (RTIs), particularly early in life. Large-scale replication of previous associations is needed, however. We investigated the association between MBL2 polymorphisms and the frequency of RTI in a large population-based birth cohort of white children.

METHODS

The frequency of RTI was prospectively assessed by annual parental questionnaires until children were 4 years of age. Thirteen polymorphisms in MBL2 were determined in 987 Dutch children. Haplotypes, previously shown to be associated with functional levels of MBL, were constructed, and their associations with the frequency of RTI during year 1, year 2, and the first 4 years of life were assessed. High-producing, intermediate-producing, and deficient MBL2 genotypes were defined on the basis of exon 1 and Y/X promoter polymorphisms.

RESULTS

No differences were found between investigated polymorphisms and haplotype frequencies in the population as a whole or between the groups with frequent, moderately frequent, or no RTIs reported. Deficient MBL2 genotypes were not associated with an increased risk of RTI (odds ratio, 0.71 [95% confidence interval, 0.25 to 2.05]) during years 1-4 of life. This was also true when year 1 and year 2 were studied separately.

CONCLUSION

These results suggest that, at the population level, MBL2 polymorphisms do not contribute to the risk of questionnaire-reported RTI in white children.

Prevalence of atopic symptoms among blood donor carriers of mannose-binding lectin variant alleles

Mannose-binding lectin (MBL) is a C-type soluble collectin involved in the innate immune response. Carriers of MBL gene variant alleles (MBLva) have decreased plasma concentrations of MBL and increased susceptibility to bacterial and viral infections. The aim of the present study is to test the hypothesis that carriers of MBLva could have a different frequency of atopic symptoms as compared to wild-type carriers. A total of 385 consecutively enrolled Caucasian blood donors were studied. Blood specimens underwent genomic analysis and genotyping for MBLva by polymerase chain reaction (PCR). MBLva carrier status was associated with a reduced frequency of allergic rhinitis (OR 0.41 [95% CI 0.2 to 0.8], chi2 = 6.98, p =.008). No relationship was found between MBLva carrier status and asthma or atopic skin symptoms. MBLva might be one of the host-related genetic factors involved in atopic disorders, namely allergic rhinitis.

Mannose-binding lectin concentrations, MBL2 polymorphisms, and susceptibility to respiratory tract infections in young men

BACKGROUND

Mannose-binding lectin (MBL) is an important component of innate immunity, and its deficiency is associated with susceptibility to recurrent infections.

METHODS

This exploratory study investigated the association of serum MBL concentrations and MBL2 gene polymorphisms with respiratory tract infections in young men. We genotyped 6 single-nucleotide polymorphisms (SNPs) in the promoter region (alleles H/L, X/Y, and P/Q) and exon 1 (variant alleles B, C, and D and wild-type allele A) of the MBL2 gene by real-time polymerase chain reaction and measured serum MBL concentrations in 111 Finnish military recruits with asthma and 362 without.

RESULTS

An MBL level below the median concentration was a significant risk factor for infections (asthma status-adjusted odds ratio [OR], 2.5 [95% confidence interval {CI}, 1.4-4.5]). Among the 6 SNPs, there was a significant association between the promoter Y/Y genotype and infections (OR, 2.3 [95% CI, 1.2-4.4]) and a borderline significant association between exon 1 variant alleles and infections (OR, 1.7 [95% CI, 0.9-3.1]), after adjustment for asthma status.

CONCLUSION

These preliminary results suggest, for the first time, an association between MBL level and respiratory tract infections in young men and a possible association between infections and MBL2 polymorphisms.

Mannan-binding lectin (MBL) polymorphism and gastric cancer risk in Japanese population

BACKGROUND

Mannan-binding lectin (MBL) is believed to be an important constituent of the innate immune system. It has been reported that the codon 54 G/A polymorphism of exon-1 affects the MBL2 gene and alters its activity.

AIMS

We investigated the association between polymorphism of the MBL2 gene and gastric cancer risk as well as Helicobacter pylori infection in a Japanese population.

METHODS

The study cohort comprised 388 gastric cancer patients and 144 healthy volunteers. Polymorphism at codon 54 of exon 1 of the MBL2 gene was investigated by PCR-based restriction fragment length polymorphism analysis.

RESULTS

There was no significant difference in the distribution of the MBL2 genotype among the gastric cancer patients and healthy controls. However, the carrier of the A allele was more prevalent among patients with a more advanced stage gastric cancer [odds ratio (OR) 1.68, 95% confidence interval (CI) 1.05-2.67; P = 0.03] and also had an increased risk of gastric cancer among patients 65 years of age or younger (OR = 1.6, 95%CI = 1.01-2.52, <0.05).

CONCLUSION

The codon 54 polymorphism of the MBL2 gene is associated with more advanced phenotypes of gastric cancer and the risk of gastric cancer in Japanese patients 65 years of age or younger.

MBL2 single nucleotide polymorphism diversity among four ethnic groups as revealed by a bead-based liquid array profiling

In the present work we established a rapid, cost-effective and high-throughput method for genotyping using a multiplexed microsphere-based suspension array platform - Luminex xMAP which enabled us to analyze 3 SNPs in the MBL2 gene promoter and 5' UTR, and 3 coding SNPs exon 1 haplotypes, associated with different levels of MBL2 expression. Using this system MBL2 diversity in four different ethnic groups, namely, Asian (Japanese), Caucasian, Hispanic and African-American-assessed. Results showed significant variability in terms of allele, genotype, and haplotype distribution. Characteristic MBL haplotype patterns were defined for each ethnic group. A prevalence of haplotypes coding functional proteins capable of complement activation and pathogen opsonization was observed. Regardless of the significant diversity of individual haplotypes, a high, almost similar (25-28%) proportion of haplotypes associated with MBL deficiency was found in the four ethic groups. The proportion of individuals homozygous for the haplotypes resulting in complete MBL2 deficiency was also significant (2-10%). Considering the role of MBL2 in innate immunity and as a clinically relevant marker, the genotyping approach developed and the knowledge of the genetic variation in different ethnic groups will be relevant to future medical genetic studies.

Host's response in otitis media: understanding genetic susceptibility

Increasing evidence is emerging on genetic factors affecting host's response to infection in the middle ear. This review summarizes current knowledge on the field and on the contribution of nonspecific barriers, innate, and adaptive immunity. Better understanding of susceptibility to this very common disease will facilitate identification of high-risk individuals and optimization of prevention and treatment.

History of respiratory infections in the first 12 yr among children from a birth cohort

Respiratory infections are the most frequent health problem in childhood. There is little precise information on how many respiratory illness episodes can be expected in a normal child. This study was designed to create reference values for the frequency of respiratory infections as recordable by history. Respiratory illnesses were recorded in a prospective birth cohort of 1314 German children born in 1990 and tracked until age 12 yr (760 children). Parents recorded the child's illnesses in a diary and answered structured questions yearly up to age 12. Age of study subjects was categorized into infancy (0-2 yr), pre-school age (3-5 yr), and school age (6-12 yr). The mean cumulative number of respiratory infection episodes up to age 12 yr was 21.9 (s.d. 9.0) episodes. In infancy, the mean annual number was 3.4 (3.7) episodes; at pre-school age, 2.3 (2.6) episodes; and at school, age 1.1 (1.2) episodes. The mean cumulative time of episodes up to age 7 yr was 20.1 (15.2) wk. Forty-five percent of the infants in the upper episode incidence tertile continued to be in the upper tertile at school age. Based on a twofold standard deviation of the mean number, up to 11 respiratory infection episodes per year in infancy, 8 episodes per year at pre-school age, and 4 episodes per year at school age could be regarded as normal. Episodes within these reference values per se should not cause unwarranted concern or intervention because of suspected immunodeficiency.

An age-dependent association of mannose-binding lectin-2 genetic variants on HIV-1-related disease in children

BACKGROUND

Mannose-binding lectin (MBL) is part of the lectin pathway of complement activation against various pathogens; however, its role in innate immune responses against HIV-1 infection in children is unknown.

OBJECTIVE

This study evaluated the effects of mannose-binding lectin-2 (MBL2) alleles on HIV-1 disease progression and central nervous system (CNS) impairment in children.

METHODS

A cohort of 1037 HIV-1-infected children enrolled in Pediatrics AIDS Clinical Trial Group protocols P152 and P300 before the availability of effective antiretroviral therapy was genotyped for MBL2 and evaluated for disease progression.

RESULTS

Children with the homozygous variant MBL2-O/O genotype were more likely to experience rapid disease progression and CNS impairment than those with the wild-type AA genotype. The effects were predominantly observed in children younger than 2 years. In unadjusted Cox proportional hazards models, children younger than 2 years with MBL2-O/O experienced more rapid disease progression (O/O vs AA: relative hazard [RH], 1.54; 95% CI, 1.07-2.22; P = .02; O/O vs A/O: RH, 2.28; 95% CI, 1.09-4.79; P = .029). Similarly, children with MBL2-O/O were more likely to experience rapid progression to CNS impairment (O/O vs A/A: RH, 2.78; 95% CI, 1.06-2.69, P = .027; O/O vs A/O: RH, 1.69; 95% CI, 1.07-7.21; P = .035). The effects remained significant after adjustment for CD4(+) lymphocyte count, plasma HIV-1 RNA, and other genotypes.

CONCLUSIONS

MBL2-O/O genotypes, which result in lower expression of MBL, are associated with more rapid HIV-1-related disease progression, including CNS impairment, predominantly in children younger than 2 years. These data suggest that MBL2 variants are associated with altered HIV-1 disease progression, particularly in young children.

Mannose-binding lectin gene polymorphisms and the development of coal workers' pneumoconiosis in Japan

BACKGROUND

Infection, immunity and genetic factors play roles in the development of coal worker's pneumoconiosis (CWP) and progressive massive fibrosis (PMF). We investigate whether the genetic polymorphisms of mannose-binding lectin (MBL), one of the key molecules of innate immunity, is associated with the susceptibility to CWP.

METHOD

MBL2 polymorphisms (codon54, promoter -221, and -550) were assessed for 197 patients with CWP (119 with nodular CWP and 78 with PMF) and 153 unexposed regional controls. Serum MBL concentrations were measured in 119 CWP patients.

RESULTS

Three polymorphisms were in linkage disequilibrium for all study populations. The MBL2 genotype and haplotypes were associated with lower serum MBL levels. The frequency of such MBL2 genotype and haplotypes were significantly higher in patients with CWP compared to controls, whereas these distributions were not different between patients with nodular CWP and those with PMF.

CONCLUSION

MBL2 polymorphisms and haplotypes may be one of the genetic determinants for the susceptibility of CWP.

The role of mannose-binding lectin in susceptibility to infection in preterm neonates

Preterm neonates are susceptible to infection due to a combination of sub-optimal immunity and increased exposure to invasive organisms. Mannose-binding lectin (MBL) is a component of the innate immune system, which may be especially important in the neonatal setting. The objective of this study was to investigate the impact of MBL on susceptibility and severity of infection in preterm neonates during their first month of life. One hundred fifty eight preterm neonates were genotyped for MBL mutations by heteroduplex analyses. Consecutive serum MBL levels were measured by ELISA and clinical and laboratory data, including blood cultures, were collected for each baby. A third of the premature neonates had genetically determined MBL deficiency. In addition, MBL levels were also low in the first week of life and lower in neonates with a wild type genotype who were less than 28 wk gestation or a birth weight of less than 1000 g, thereby increasing the number of neonates with a low MBL level at birth. MBL deficiency was associated with an increased risk of sepsis (p < 0.01). This study indicates that MBL levels are low in neonates at birth and renders premature neonates to an increased risk of infection.

Genetic approach to pediatric septic shock

Septic shock is a complex and heterogeneous clinical syndrome, triggered by infection, and having significant morbidity and mortality in children. Emerging data indicate that the genetic make-up of the pediatric host may have a strong influence on the development and outcome of septic shock in children. Herein, we review this broad topic by focusing on pediatric-specific data (both recent and historical), as well as the broad topics of SNPs, genome-wide association studies and epigenetics. The historical and emerging data strongly suggest that a genetics-based perspective will need to be considered in future investigations and strategies aimed at improving the outcome of children with septic shock.

Mannose-binding lectin in HIV infection

Infection with HIV represents a significant global health problem, with high infection rates and high mortality worldwide. Treatment with antiretroviral therapy is inaccessible to many patients and efficacy is limited by development of resistance and side effects. The interactions of HIV with the human immune system, both innate and humoral, are complex and complicated by the profound ability of the virus to disable the host immune response. Mannose-binding lectin, a component of the innate immune system, has been demonstrated to play a role in host-virus interactions. This protein may have a key role in determining host susceptibility to infection, pathogenesis and progression of disease, and may contribute to the extensive variability of host response to infection. Further understanding and manipulation of the mannose-binding lectin response may represent a target for immunomodulation in HIV infection, which may, in conjunction with highly active antiretroviral therapy, allow development of a novel therapeutic approach to HIV infection.

Complex two-gene modulation of lung disease severity in children with cystic fibrosis

Although cystic fibrosis (CF) is a monogenic disease, its clinical manifestations are influenced in a complex manner. Severity of lung disease, the main cause of mortality among CF patients, is likely modulated by several genes. The mannose-binding lectin 2 (MBL2) gene encodes an innate immune response protein and has been implicated as a pulmonary modifier in CF. However, reports have been conflicting, and interactions with other modifiers have not been investigated. We therefore evaluated the association of MBL2 with CF pulmonary phenotype in a cohort of 1,019 Canadian pediatric CF patients. MBL2 genotypes were combined into low-, intermediate-, and high-expression groups based on MBL2 levels in plasma. Analysis of age at first infection with Pseudomonas aeruginosa demonstrated that MBL2 deficiency was significantly associated with earlier onset of infection. This MBL2 effect was amplified in patients with high-producing genotypes of transforming growth factor beta 1 (TGFB1). Similarly, MBL2 deficiency was associated with more rapid decline of pulmonary function, most significantly in those carrying the high-producing TGFB1 genotype. These findings provide evidence of gene-gene interaction in the pathogenesis of CF lung disease, whereby high TGF-beta1 production enhances the modulatory effect of MBL2 on the age of first bacterial infection and the rate of decline of pulmonary function.

Mannose-binding lectin deficiency is associated with early onset of polyarticular juvenile rheumatoid arthritis: a cohort study

Background

Mannose-binding lectin (MBL) is an innate immune protein. The aim of our study was to determine whether genetically determined MBL deficiency is associated with susceptibility to juvenile rheumatoid arthritis (JRA) and whether MBL2 genotypes are associated with JRA severity.

Methods

In a retrospective cohort study of 218 patients with polyarthritis (n = 67) and oligoarthritis (n = 151), clinical and laboratory disease variables were obtained by clinical examination and chart reviews. Healthy Caucasian adults (n = 194) served as control individuals. MBL2 gene mutations were determined by Taqman analysis to identify genotypes with high, medium and low expression of MBL. Functional MBL plasma concentrations were measured using enzyme-linked immunosorbent assay. Associations between clinical and laboratory variables and MBL2 genotypes were determined by Kruskal-Wallis and χ² tests.

Results

MBL2 genotype frequencies were similar in polyarthritis and oligoarthritis patients as compared with control individuals. MBL plasma concentrations were associated with the high, medium and low MBL genotype expression groups (P < 0.01). In polyarthritis patients, the presence of low-expressing (deficient) MBL2 genotypes was associated with early age at onset of disease (P = 0.03). In oligoarthritis patients, patients with low-expressing MBL2 genotypes were more often in remission (81%) than patients in the medium (54%) and high (56%) genotype groups (P = 0.02). The remaining clinical and laboratory variables, such as arthritis severity index, presence of radiographic erosions and antinuclear antibody positivity, were not associated with MBL2 genotypes.

Conclusion

Genetically determined MBL deficiency does not increase susceptibility to JRA, but MBL deficiency is associated with a younger age at onset of juvenile polyarthritis. On the other hand, MBL-deficient children with juvenile oligoarthritis are more often in remission. Therefore, MBL appears to play a dual role in JRA.

Mannose-binding lectin haplotypes influence Brucella abortus infection in the water buffalo (Bubalus bubalis)

A case-control study established that the haplotype pair HYA/HYA at the MBL (mannose binding lectin) locus of water buffalo is associated with resistance to Brucella abortus infection (P < 10(-7)) and the haplotype pairs LYD/LYD with susceptibility to the same pathogen (P < 10(-7)). The subjects included in the present study were tested twice-at a 1-month interval-for the presence of anti-B. abortus antibodies in the serum by agglutination, complement fixation and flow cytometry. Cases (335 subjects) included animals consistently positive to all these tests; controls (335 subjects) comprised animals exposed yet negative by the same tests. The serum from genetically resistant subjects displayed in vitro significantly higher antibacterial activity compared to the serum from genetically susceptible subjects, lending biological significance to the results from the association study. Inhibition of the antibacterial activity following heat treatment of the serum, addition of specific MBL inhibitors (EDTA, mannose, N-acetyl-D: -glucosamine) or anti-human MBL antiserum provide convincing evidence that the antibacterial activity present in the serum results from the interaction between MBL and B. abortus. A replication study (comprising 100 cases and 100 controls) confirmed the results from the original study.

Possible disease-modifying factors: the mannan-binding lectin pathway and infections in hereditary angioedema of children and adults

Introduction

Hereditary angioedema (HAE) is caused by mutations in the C1inh gene, leading to dysfunction of the C1-esterase inhibitor (C1-INH). C1-INH interacts with MASP-1 and MASP-2 proteases, participating in the mannan-binding lectin (MBL) pathway of complement activation. The aim of the study was to investigate the contribution of possible changes in MBL/MASP-2 complex activity and Helicobacter pylori, hepatitis B virus (HBV), and hepatitis C virus (HCV) infections to the severity and frequency of clinical symptoms of HAE.

Materials and Methods

The study was performed in 65 patients with HAE and 113 healthy persons. The parameters measured were C1-INH, C4, MBL concentration and MBL/MASP-2 complex activity, and serological markers of H. pylori, HBV, and HCV infection. Scores for the frequency and severity of HAE symptoms were determined.

Results

HAE scores were significantly higher in patients whose C1-INH activity did not exceed 10% than in patients with activity of 10-52% (p=0.016). No significant differences were found in the median levels of MBL concentration and MBL/MASP-2 complex activity between patients and the control group. There was a slight association between contact with H. pylori in patients and HAE symptom score (p=0.052, not significant). Adult patients showed a 2.6-times higher frequency of anti-HBc than the general population. HBV DNA was negative in anti-HBc(+) patients.

Conclusions

These results suggest that the MBL complement activation pathway itself does not contribute to the frequency of angioedema attacks. Infections with H. pylori and HBV may slightly influence the disease score (not significant).

Mannose-binding lectin enhances Toll-like receptors 2 and 6 signaling from the phagosome

Innate immunity is the first-line defense against pathogens and relies on phagocytes, soluble components, and cell-surface and cytosolic pattern recognition receptors. Despite using hard-wired receptors and signaling pathways, the innate immune response demonstrates surprising specificity to different pathogens. We determined how combinatorial use of innate immune defense mechanisms defines the response. We describe a novel cooperation between a soluble component of the innate immune system, the mannose-binding lectin, and Toll-like receptor 2 that both specifies and amplifies the host response to Staphylococcus aureus. Furthermore, we demonstrate that this cooperation occurs within the phagosome, emphasizing the importance of engulfment in providing the appropriate cellular environment to facilitate the synergy between these defense pathways.

Regional association-based fine-mapping for sodium-lithium countertransport on chromosome 10

BACKGROUND

Increased erythrocyte sodium-lithium countertransport (SLC) has been observed in patients with essential hypertension. Consistent evidence of genetic linkage was shown for SLC on chromosome 10, and a region of interest was localized between 26 and 56 Mb.

METHODS

This study surveyed single nucleotide polymorphisms (SNPs) in 54 genes that reside in the region of interest, and investigated their association with SLC and blood pressure. These SNPs were genotyped in 1,133 non-Hispanic white individuals from 255 pedigrees comprising the second phase of the Rochester Family Heart Study. The variance-components-based genetics software package SOLAR was used for evaluating whether an SNP contributed to a significant fraction of the trait heritability.

RESULTS

Of the 77 SNPs surveyed in this study across the region of interest, four SNPs were associated with SLC (P < 0.04), five SNPs were associated with blood pressure (P < 0.04), and two SNPs in mannose-binding lectin 2 (MBL2) were associated with both phenotypes. In general, the pairwise linkage disequilibrium among the genotyped SNPs was low.

CONCLUSIONS

This fine-mapping survey of genetic variation in a linkage region of interest provides overall support for association-mapping for SLC on chromosome 10. Genes significantly associated with systolic blood pressure and/or SLC in these families will be prioritized for future studies.

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.

MBL2 variants in relation to common childhood infections and atopy-related phenotypes in a large German birth cohort

Mannose-binding lectin (MBL) is considered an important component of innate immunity. Four functional MBL2 alterations in codons 52, 54, 57 and in the promoter at position c.1-290 are correlated with significantly lowered MBL serum levels. These variants have been associated with susceptibility to a variety of infectious agents as well as with various immunologic disorders including asthma. To reassess these observations, we analysed the four above mentioned MBL2 variants in 749 children, who were recruited by the German Multicenter Allergy Study and were prospectively evaluated for common respiratory childhood infections and atopy-related phenotypes from birth up to the age of 11 yr. We performed genotyping by melting curve analysis using fluorescence resonance energy transfer probes and the LightCycler. In contrast to previous studies, we found an association of MBL2 variants neither with the frequency of common respiratory childhood infections at any age nor with asthma or other atopy-related phenotypes. Our data suggest that MBL deficiency does not represent a pre-disposing factor for respiratory infections or atopic disorders in infants and children.

Mannose-binding lectin (MBL) genotype in relation to risk of nosocomial infection in pre-term neonates in the neonatal intensive care unit

Mannose-binding lectin (MBL) plays an important role in the innate immune response. Three alleles in the MBL gene, and one allele of the promoter, independently cause low serum MBL levels as compared with the wild-type. This study investigated the relationship between MBL genotype and the occurrence of nosocomial infection among neonates in a neonatal intensive care unit (NICU). Prospectively gathered information concerning nosocomial infection was available for 742 neonates from a recently performed surveillance study in an NICU. DNA was isolated from Guthriecards for a subgroup of 204 neonates who stayed in the NICU for > or =4 days. After a pre-PCR for the MBL gene in blood spots on Guthriecards, mutations were analysed by real-time PCR to detect six mutations in the MBL gene. An MBL genotype could be determined for 186 neonates. As compared to term neonates, genotypes encoding MBL-deficient haplotypes were significantly more prevalent among pre-term neonates. Forty-one of these neonates developed sepsis, with blood cultures yielding coagulase-negative staphylococci in 25 cases. Pneumonia occurred in 30 cases, with various causative organisms. No relationship was found between MBL genotype and the risk of nosocomial sepsis or pneumonia, even after correction for birth-weight, perhaps because of an insufficient correlation between genotype and the concentration of functional MBL. In addition, most bloodstream infections in the NICU were caused by coagulase-negative staphylococci, to which MBL binds poorly.

Serum mannose-binding lectin levels are linked with respiratory syncytial virus (RSV) disease

The innate immune response facilitates the quality of the adaptive immune response and is critical to an individual's susceptibility to infection and disease. Mannose-binding lectin (MBL) is a plasma protein with anti-microbial properties that binds a wide range of pathogens to flag them for immune destruction independent of antibodies. In this study, serum MBL levels were measured in 81 children <5 years old experiencing acute respiratory syncytial virus infection and in 40 control children to determine the association with disease severity. Almost 70% of all RSV-infected children had low to intermediate MBL levels (<500 ng/ml) compared to controls, and most of the <6 months old RSV interned patients had low to intermediate levels. No differences were detected in MBL levels between case and control children <1 month old. Analysis of the T-cell compartment in peripheral blood mononuclear cells (PBMC) from acute RSV-infected and control children showed that the percent CD4+ T cells was statistically lower in RSV-infected children > or =6 months old compared to controls, while the percent CD8+ T cells in RSV-infected and control PBMC was generally similar. These results suggest that low serum MBL levels may be a marker of RSV disease severity in children and that MBL may be important in limiting RSV disease pathogenesis.

Mannose binding lectin gene polymorphisms and asthma

BACKGROUND

Bronchial asthma is a chronic inflammatory disorder of the airways. Recently, it has been suggested that complement plays significant roles in asthma. Mannose-binding lectin (MBL) is one of the key molecules in complement activation pathways that are associated with several infectious and immune disorders.

SUBJECTS AND METHOD

To investigate whether MBL plays roles in asthma, we analysed MBL2 polymorphisms (allele B, H/L and Y/X) and plasma MBL levels in a Japanese adult population including 232 healthy controls and 579 asthmatics.

RESULTS

Although there was linkage disequilibrium among the three polymorphisms, each polymorphism significantly affects serum MBL levels independently. However, there were no significant differences between asthmatics and controls in MBL2 genotype distribution and in MBL concentrations [1.47+/-0.07(SE) mg/L for asthmatics and 1.66+/-0.14 mg/L for controls, P=0.2]. MBL levels and genotype have no significant relationship with serum IgE, pulmonary functions, and the severity of asthma.

CONCLUSION

Although plasma MBL levels depend on the MBL2 polymorphisms, these polymorphisms and plasma MBL levels are not associated with the asthma phenotype.

Association of polymorphisms in the mannose-binding lectin gene and pulmonary morbidity in preterm infants

Deficiency in the collectin mannose-binding lectin (MBL) increases the risk for pulmonary and systemic infections and its complications in children and adults. The aim of this prospective cohort study was to determine the genetic association of sequence variations within the MBL gene with systemic infections and pulmonary short- and long-term complications in preterm infants below 32 weeks gestational age (GA). Three single-nucleotide polymorphisms (SNPs) in the coding region and one SNP in the promotor region of MBL2 were genotyped by direct sequencing and with sequence-specific probes in 284 newborn infants <32 weeks GA. Clinical variables were comprehensively monitored. An association was found between two SNPs and the development of bronchopulmonary dysplasia (BPD), defined as persistent oxygen requirement at 36 weeks postmenstrual age, adjusting for covariates GA, grade of respiratory distress syndrome and days on mechanical ventilation (rs1800450 (exon 1 at codon 54, B variant): odds ratio dominant model (OR)=3.59, 95% confidence interval (CI)=1.62-7.98; rs7096206 (-221, X variant): OR=2.40, 95% CI=1.16-4.96). Haplotype analyses confirmed the association to BPD, and a single haplotype (frequency 56%) including all SNPs in their wild-type form showed a negative association with the development of BPD. We detected no association between the MBL gene variations and the development of early-onset infections or further pulmonary complications. Frequent variants of the MBL gene, leading to low MBL concentrations, are associated with the diagnosis of BPD in preterm infants. This provides a basis for potential therapeutic options and further genetic and proteomic analysis of the function of MBL in the resistance against pulmonary long-term complications in preterm infants.

Clinical and genetic risk factors for pneumonia in systemic lupus erythematosus

OBJECTIVE

To define the contribution of polymorphisms in genes encoding tumor necrosis factor (TNF), mannose-binding lectin (MBL), and Fcgamma receptor IIa (FCGR2A) as well as clinical factors, to the development of pneumonia in patients with systemic lupus erythematosus (SLE).

METHODS

We studied 282 SLE patients from a multiethnic cohort. Pneumonia events and clinical risk factors for pneumonia were identified through medical record review. Genotyping was performed for MBL (+223, +230, and +239), TNF (-308, -238, and +488), and FCGR2A (-131H/R) polymorphisms. Univariate analyses were performed to identify clinical and genetic risk factors for pneumonia. Covariates for multivariate analysis included sex, ethnicity, treatment with immunomodulators, and leukopenia.

RESULTS

Forty-two patients (15%) had at least 1 episode of pneumonia. Polymorphism of the TNF gene, particularly the -238A allele and a related haplotype, revealed the most striking and consistent association with pneumonia in univariate analyses. Results of multivariate analyses indicated an odds ratio (OR) for the TNF -238A allele of 3.5 (P = 0.007) and an OR for the related haplotype of 5.4 (P = 0.001). Male sex, treatment with immunomodulators, and leukopenia also influenced the risk of pneumonia.

CONCLUSION

These findings suggest that specific TNF variants may identify SLE patients who are at particularly high risk of developing pneumonia. Given the prevalence and excessive morbidity associated with pneumonia in SLE, these findings have clinical relevance and provide insight into the pathogenesis.

Lung cancer survival and functional polymorphisms in MBL2, an innate-immunity gene

BACKGROUND

The relationship among chronic inflammation, innate immunity, and cancer is well established. Mannose-binding lectin (MBL) is a key player in innate immunity. Five polymorphisms in the promoter and first exon of the MBL2 gene alter the expression and function of MBL in humans and are associated with inflammation-related disease susceptibility. These five polymorphisms create six well-characterized haplotypes that result in lower (i.e., LYB, LYC, HYD, and LXA) or higher (i.e., HYA and LYA) serum MBL concentrations. We investigated whether survival of patients with lung cancer was associated with these polymorphisms.

METHODS

We used a multivariable Cox proportional hazards model to study the association between MBL2 polymorphisms and their haplotypes and diplotypes in 558 white and 173 African American patients with non-small-cell lung cancer in the Baltimore, MD, area and lung cancer mortality. Smoking history and race were obtained from interviews, tumor stage was obtained from medical records, and cause of death was obtained from the National Death Index. All statistical tests were two-sided.

RESULTS

We found a statistically significant association between the X allele of the promoter Y/X polymorphism (which results in a lower serum MBL concentration) and improved lung cancer survival among white patients (risk ratio [RR] of death from lung cancer with X/X or X/Y genotype compared with Y/Y genotype = 0.61, 95% confidence interval [CI] = 0.46 to 0.81) but not among African American patients (RR = 1.11, 95% CI = 0.69 to 1.77). The associations among white patients were strongest in heavy smokers and were independent of stage. We also found a statistically significant interaction between the Y/X polymorphism and race for lung cancer survival (P(interaction) = .019). The MBL2 LXA haplotype and XA/B diplotype, which are also associated with low serum MBL levels, were statistically significantly associated with improved lung cancer survival among white patients.

CONCLUSION

The functional Y/X polymorphism of the innate-immunity gene MBL2 and MBL2 haplotypes and diplotypes appear to be associated with lung cancer survival among white patients.

The role of human innate immune factors in nasal colonization by Staphylococcus aureus

Staphylococcus aureus colonization of the human nares predisposes to sometimes severe auto-infection. To investigate whether genetic polymorphism affects the S. aureus carriage status, sequence variation in alpha-defensin and beta-defensin, and mannose-binding lectin (MBL) genes were determined for a group of volunteers (n=109) with known S. aureus nasal carriage status. DEFA1/3 expression was measured in a subset of the volunteers (n=32). None of the single nucleotide polymorphisms studied could clearly distinguish the (non) carriage groups. S. aureus carriers differed from non-carriers in baseline level of HNP1-3 peptide production (median: 218 versus 89mug/ml, P=0.016). No association between HNP1-3 levels and the individual sequence polymorphisms was documented. The combined copy numbers of DEFA1/A3 genes ranged from 5 to 23 per diploid genome. A linear correlation between combined copy numbers and HNP1-3 peptide concentrations in nasal secretions of non-carriers was noted (r(2)=0.8991). DEFA3 gene was absent in 25% of the individuals. MBL haplotype A was overrepresented in persistent S. aureus carriers (87% vs. 67%; P=0.038). In conclusion, defensin gene polymorphism, both in sequence and in gene copy numbers, does not seem to be involved in S. aureus carriage predisposition. However, MBL haplotypes do so significantly. Baseline HNP1-3 production is more the consequence of S. aureus colonization than a reason for the (non) carrier status.

Evidence of an association between mannose binding lectin codon 54 polymorphism and adenoidectomy and/or tonsillectomy in children

Mannose binding lectin (MBL) is a calcium-dependent lectin that plays an important role innate immunity by activating the complement pathway. There have been a number of studies describing an association between the MBL genotype and disease susceptibility. MBL deficiency has been described as one of the factors leading to a number of infections in children with recurrent upper respiratory tractus infections (URTI). We hypothesized that MBL deficiency may be associated with recurrent URTI, which requires adenoidectomy and/or adenotonsillectomy. In this study to clarify this hypothesis we investigated whether there may be an association between two low producing MBL variants and adenoidectomy and/or tonsillectomy due to recurrent URTI in children. Blood samples were collected, adenoidectomy and/or tonsillectomy due to recurrent URTI and 50 controls (mean age 80.53 +/- 32.62 months). In all patients and controls codon 54 and codon 57 polymorphisms of the MBL gene were analyzed. None of the subjects from the patient group and control group carried codon 57 polymorphism of the MBL gene. The frequency of low-level MBL genotypes (AB and BB) for codon 54 polymorphism in the patient group was found to be significantly higher compared to the control subjects (55.7% versus 14%) (p<0.001). This study shows that the presence of low-level MBL alleles is associated with adenoidectomy and/or tonsillectomy caused by recurrent URTI in children.

Low pretransplantation mannose-binding lectin levels predict superior patient and graft survival after simultaneous pancreas-kidney transplantation

Simultaneous pancreas-kidney transplantation (SPKT) is the treatment of choice for patients with type 1 diabetes and renal failure. However, this procedure is characterized by a high rate of postoperative infections, acute rejection episodes, and cardiovascular mortality. The lectin pathway of complement activation contributes to cardiovascular disease in diabetes and may play an important role in inflammatory damage after organ transplantation. This study therefore sought to determine how mannose-binding lectin (MBL), a major recognition molecule of the lectin pathway of complement activation, influences outcome after SPKT. MBL serum levels were determined in 99 and MBL genotypes in 97 consecutive patients who received an SPKT from 1990 through 2000 and related to patient and graft survival. At 12 yr, cumulative death-censored kidney graft survival was 87.5% in patients with an MBL level <400 ng/ml and 74.8% in the group with MBL levels >400 ng/ml (P = 0.021). Pancreas graft survival was significantly better in patients with low MBL levels (P = 0.016). MBL levels >400 ng/ml were associated with a hazard ratio of 6.28 for patient death (95% confidence interval 1.8 to 20.3; P = 0.003). Accordingly, survival was significantly better in recipients with MBL gene polymorphisms associated with low MBL levels. These findings identify MBL as a potential risk factor for graft and patient survival in SPKT. It is hypothesized that MBL contributes to the pathogenesis of inflammation-induced vascular damage both in the transplanted organs and in the recipient's native blood vessels.

Second-generation nanofiltered plasma-derived mannan-binding lectin product: process and characteristics

BACKGROUND AND OBJECTIVES

Mannan-binding lectin (MBL) is an important component of the innate immune defence; it binds to carbohydrate structures on pathogenic micro-organisms resulting in complement activation and opsonization. Individuals with low MBL levels are at risk of recurrent and severe infections. Substitution therapy with plasma-derived MBL is a promising treatment of diseases associated with MBL deficiency. A first-generation MBL product has been shown to be safe and well tolerated, and patients have benefited from MBL treatment. Following is a description of the development of a nanofiltered second-generation MBL product from Cohn fraction III, with the use of a new affinity matrix for MBL purification and the characteristics of this improved product.

MATERIALS AND METHODS

Carbohydrate-based gels were comparatively screened as affinity matrices. MBL was extracted from fraction III, and affinity purified on a Superdex 200 pg column. The eluted material underwent two virus reduction steps: filtration through Planova 20N and solvent/detergent treatment. It was further purified by anion-exchange and gel-filtration chromatography. The affinity eluate and the final MBL fraction were characterized by protein chemical, immunological, and functional assays.

RESULTS

In production scale, Superdex 200 pg was found to be superior to other carbohydrate-based matrices, and MBL was affinity purified from fraction III with a yield of 70%. The viral safety was increased by performing a nanofiltration of the affinity eluate through Planova 20N with a minimal loss of MBL. The purity of the final MBL fraction was 53% excluding the MBL-associated serine proteases (MASP). The product consisted of high-oligomeric MBL, with two dominating forms, and with MASP-1, -2, -3 and 19 kDa MBL-associated protein (MAp19). Only a few protein impurities were present, the major being alpha2-macroglobulin. MBL formed complexes with alpha2-macroglobulin bridged by MASP-1 covalently attached to the latter. The functional activity, assessed by mannan-binding activity and opsonic function, was intact, whereas half of the C4 activating capacity was lost during the production process.

CONCLUSION

A second-generation MBL process was developed with an average yield of 50%. It was possible to nanofilter the MBL-MASP complexes through Planova 20N with only a minor loss resulting in an increased safety profile of this MBL product.

Functional polymorphisms in the FCN2 gene are not associated with invasive pneumococcal disease

L-ficolin is a pattern-recognition molecule which binds lipoteichoic acid and Gram-positive bacteria and activates the lectin pathway of complement. Five common functional polymorphisms have recently been identified in the FCN2 gene which encodes L-ficolin: three promoter polymorphisms (at positions -986, -602 and -4) which affect serum L-ficolin concentration, and two non-synonymous polymorphisms (Thr236Met and Ala258Ser) which influence carbohydrate binding. We studied the frequencies of these polymorphisms in individuals with invasive pneumococcal disease (IPD) and a control group. Although the five FCN2 polymorphisms were each present in the UK Caucasian population studied, no significant associations were observed between the FCN2 polymorphisms and susceptibility to IPD. This is in contrast to mannose-binding lectin deficiency, which we have previously shown to be associated with increased susceptibility to IPD. Although we are unable to exclude small effects of FCN2 genetic variation on susceptibility to IPD, the result suggests that L-ficolin may not be critical for host defence against pneumococcal infection.

Anti-influenza A virus activities of mannan-binding lectins and bovine conglutinin

Mannan-binding lectin (MBL) and bovine conglutinin (BKg) belong to the collectin family, which is involved in first-line host defense against various infectious agents. We have previously reported that human MBL inhibited type A influenza viral hemagglutination, infection and spreading to adjacent cells without complement activation. In this study, we investigated the direct antiviral activities of bovine MBL, rabbit MBL and BKg. All collectins used in this study inhibited viral infectivity and hemagglutination at concentrations of 0.02-0.3 microg/ml. They also demonstrated inhibitory activity against viral spreading. Like human MBL, bovine MBL and BKg showed antiviral activities at their physiological concentrations. These results suggest that mammalian MBLs and BKg may inhibit the spread of influenza A virus through the bloodstream.

Genetic influences on mannan-binding lectin (MBL) and mannan-binding lectin associated serine protease-2 (MASP-2) activity

The lectin pathway of the complement system is activated when Mannan-binding lectin (MBL) in complex with MASP-2 binds microorganisms. Polymorphisms in both genes are responsible for low serum levels, which associate with increased risk of infection and autoimmune disease. The present study includes 1215 MBL measurements and 1214 MASP-2 activity measurements in healthy Danish adult twins. Total MASP-2 activity was estimated by C4 cleaving activity of samples diluted in an excess of MBL. Twin-twin correlations were higher in monozygotic (MZ) than in dizygotic (DZ) twins for both traits. Heritabilites of MBL levels and MASP-2 activity were estimated using structural equation modeling allowing assessment of the contribution of common genes affecting both traits. The estimated heritability was 0.77 [95% CI 0.64;0.91] for MBL levels and 0.75 [95% CI 0.59;0.81] for MASP-2 activity with the presence of additive genetic factors, shared environmental factors, and non-shared environmental factors. The genetic correlation, i.e., common genetic factors affecting MBL and MASP-2 activity was estimated to r(g) = 0.34 [0.25;0.42]. The data indicate a strong genetic influence for the serum levels of MBL and for MASP-2 activity with a significant genetic correlation between the two traits.