Mannose binding lectin (MBL) in autoimmunity and its role in systemic lupus erythematosus (SLE)

Mannose binding lectin (MBL) is an important element of the innate immune system. MBL binding leads to activation and cleavage of C3 and C4 suggesting the role of MBL pathway for opsonization and/ phagocytosis. The role of adaptive immune response in development of pathogenic autoantibodies in various autoimmune diseases is well understood. The link between innate and acquired immunity is helpful for understanding the immunopathogenesis of autoimmune diseases. Evidence that innate immune system could lead to autoimmunity is growing with the major recent concept of autoimmune disease pathogenesis is related to impaired apoptotic cell clearance. MBL have been demonstrated to facilitate clearance of apoptotic cells in vivo and in vitro. Low MBL serum levels resulting in impaired apoptotic clearance have shown to enhance the risk for infection and high MBL serum levels and high MBL activity have been associated with inflammatory autoimmune diseases like Systemic Lupus Erythematosus (SLE) that in turn results in to tissue damage and finally leads to organ damage. Serum MBL levels fluctuate during the course of SLE disease activity and MBL genotypes have been found to be useful in assessing the risk of infection during immunosuppressive treatment the majority of the SLE patients receive. This review focuses on the genetic and molecular characteristics of MBL and discusses MBL disease association in autoimmunity with special emphasis on SLE.

Analysis of evolutionarily conserved innate immune components in coral links immunity and symbiosis

Reef-building corals are representatives of one of the earliest diverging metazoan lineages and are experiencing increases in bleaching events (breakdown of the coral-Symbiodinium symbiosis) and disease outbreaks. The present study investigates the roles of two pattern recognition proteins, the mannose binding lectin Millectin and a complement factor C3-like protein (C3-Am), in the coral Acropora millepora. The results indicate that the innate immune functions of these molecules are conserved and arose early in evolution. C3-Am is expressed in response to injury, and may function as an opsonin. In contrast, Millectin expression is up-regulated in response to lipopolysaccharide and peptidoglycan. These observations, coupled with localization of Millectin in nematocysts in epidermal tissue, and reported binding of pathogens, are consistent with a key role for the lectin in innate immunity. Furthermore, Millectin was consistently detected binding to the symbiont Symbiodinium in vivo, indicating that the Millectin function of recognition and binding of non-self-entities may have been co-opted from an ancient innate immune system into a role in symbiosis.

Effects of mannose-binding lectin polymorphisms on irinotecan-induced febrile neutropenia

OBJECTIVE

Mannose-binding lectin (MBL) is important in the innate immune response. MBL2 gene polymorphisms affect MBL expression, and genotypes yielding low MBL levels have been associated with an elevated risk for infections in hematological cancer patients undergoing chemotherapy. However, these reported associations are inconsistent, and data on patients with solid tumors are lacking. Here, we investigated the effects of MBL2 genotypes on irinotecan-induced febrile neutropenia in patients with solid tumors.

PATIENTS AND METHODS

Irinotecan-treated patients were genotyped for the MBL2 gene. Two promoter (-550 H/L and -221 X/Y) and three exon polymorphisms (52 A/D, 54 A/B, and 57 A/C) were determined, together with known risk factors for irinotecan-induced toxicity. Neutropenia and febrile neutropenia were recorded during the first course.

RESULTS

Of the 133 patients, 28% experienced severe neutropenia and 10% experienced febrile neutropenia. No associations were found between exon polymorphisms and febrile neutropenia. However, patients with the H/H promoter genotype, associated with high MBL levels, experienced significantly more febrile neutropenia than patients with the H/L and L/L genotypes (20% versus 13% versus 5%). Moreover, patients with the HYA haplotype encountered significantly more febrile neutropenia than patients without this high MBL-producing haplotype (16% versus 4%). In the subgroup with wild-type exon polymorphisms (A/A), patients with the high MBL promoter phenotype had the highest incidence of febrile neutropenia, regardless of known risk factors.

CONCLUSION

Patients with high MBL2 promoter genotypes and haplotypes seem more at risk for developing febrile neutropenia. If confirmed, these preliminary findings may contribute to more individualized approaches of irinotecan treatment.

Involvement of lectin pathway activation in the complement killing of Giardia intestinalis

Giardia intestinalis (syn. G. lamblia, G. duodenalis) is a flagellated unicellular eukaryotic microorganism that commonly causes diarrheal disease throughout the world. In humans, the clinical effects of Giardia infection range from the asymptomatic carrier state to a severe malabsorption syndrome possibly due to different virulence of the Giardia strain, the number of cysts ingested, the age of the host, and the state of the host immune system at the time of infection. The question about how G. intestinalis is controlled by the organism remains unanswered. Here, we investigated the role of the complement system and in particular, the lectin pathway during Giardia infections. We present the first evidence that G. intestinalis activate the complement lectin pathway and in doing so participate in eradication of the parasite. We detected rapid binding of mannan-binding lectin, H-ficolin and L-ficolin to the surface of G. intestinalis trophozoites and normal human serum depleted of these molecules failed to kill the parasites. Our finding provides insight into the role of lectin pathway in the control of G. intestinalis and about the nature of surface components of parasite.

Essential role of mannose-binding lectin-associated serine protease-1 in activation of the complement factor D

The complement system is an essential component of innate immunity, participating in the pathogenesis of inflammatory diseases and in host defense. In the lectin complement pathway, mannose-binding lectin (MBL) and ficolins act as recognition molecules, and MBL-associated serine protease (MASP) is a key enzyme; MASP-2 is responsible for the lectin pathway activation. The function of other serine proteases (MASP-1 and MASP-3) is still obscure. In this study, we generated a MASP-1- and MASP-3-deficient mouse model (Masp1/3-/-) and found that no activation of the alternative pathway was observed in Masp1/3-/- serum. Mass spectrometric analysis revealed that circulating complement factor D (Df) in Masp1/3-/- mice is a zymogen (pro-Df) with the activation peptide QPRGR at its N terminus. These results suggested that Masp1/3-/- mice failed to convert pro-Df to its active form, whereas it was generally accepted that the activation peptide of pro-Df is removed during its secretion and factor D constitutively exists in an active form in the circulation. Furthermore, recombinant MASP-1 converted pro-Df to the active form in vitro, although the activation mechanism of pro-Df by MASP-1 is still unclear. Thus, it is clear that MASP-1 is an essential protease of both the lectin and alternative complement pathways.

L-ficolin (ficolin-2) insufficiency is associated with combined allergic and infectious respiratory disease in children

We previously reported an association between relative L-ficolin deficiency and recurrent respiratory infections co-existing with allergic disorders in children. To confirm and extend this preliminary finding, we performed a prospective study on children of a similar age (mean 8.9 years) designed to establish whether the principal relationship was with infection or allergy. Serum L-ficolin values in healthy children were normally distributed with a mean value of 3838 ng/ml. L-ficolin concentrations were generally lower in patients with asthma and/or allergic rhinitis with (mean 3413 ng/ml; p=0.02) or without (3512 ng/ml; p<0.07) respiratory infections, but not in patients with respiratory infections without allergic disease (3623 ng/ml; p=0.2). The lower average values in the group comprised of children with respiratory allergy and infections were largely due to a high proportion of very low values: 18.3% had values below 2150 ng/ml compared to only 5.5% of healthy controls (OR=3.9; p=0.01). This relationship was not apparent in the groups characterized by allergy without infection or infections without allergy. An association between mannan-binding lectin (MBL) insufficiency and recurrent respiratory infections was also confirmed. One of the patients was MASP-2 deficient, evidenced both by MASP2 genotyping and by lectin pathway activity measurement. In conclusion, L-ficolin may confer some protection from microorganisms that exacerbate allergic inflammation in the lung and its relative deficiency may contribute to enhanced susceptibility to respiratory infections. MBL insufficiency and MASP-2 deficiency are risk factors for recurrence of infections independently of allergic disease.

Multiple routes of complement activation by Mycobacterium bovis BCG

Mycobacterium tuberculosis is the leading cause of infectious disease in humans in the world. It evades the host immune system by being phagocytosed by macrophages and residing intracellularly. Complement-dependent opsonisation of extracellular mycobacteria may assist them to enter macrophages. This work examines in detail the mechanisms of complement activation by whole mycobacteria using Mycobacterium bovis BCG as a model organism. M. bovis BCG directly activates the classical, lectin and alternative pathways, resulting in fixation of C3b onto macromolecules of the mycobacterial surface. Investigation into the classical pathway has shown direct binding of human C1q to whole mycobacteria in the absence of antibodies. Most human sera contain IgG and IgM-anti-(M. bovis BCG), and pre-incubation with human immunoglobulin enhances C1q binding to the bacteria. Therefore classical pathway activation is both antibody-independent and dependent. The bacteria also activate the alternative pathway in an antibody-independent manner, but Factor H also binds, suggesting some regulation of amplification by this pathway. For the lectin pathway we have demonstrated direct binding of both MBL and L-ficolin from human serum to whole mycobacteria and subsequent MASP2 activation. H-ficolin binding was not observed. No M. bovis BCG cell surface or secreted protease appears likely to influence complement activation. Together, these data provide a more detailed analysis of the mechanisms by which M. bovis BCG interacts with the complement system.

Association between mannose-binding lectin and HIV infection and progression in a Chinese population

Mannose-binding lectin (MBL) is a circulating pattern recognition molecule involved in the innate immune system that mediates phagocytosis and activates complement by binding to a carbohydrate extremity. Some MBL genetic polymorphisms result in deficient protein levels and increased susceptibility to infection. The objective of this study was to investigate the association between MBL2 exon 1 polymorphisms, serum levels of normal MBL, and HIV-1 infection and progression in a Chinese population. A total of 1075 adult patients infected with HIV-1 (532 male and 543 female) were recruited. The genotype of 145 patients was determined and the genotype frequencies compared with healthy population controls. The disease status of patients was evaluated for different MBL2 genotypes and normal MBL serum levels. MBL2 exon 1 polymorphisms (A/O or O/O) were significantly more common in HIV-1-infected patients than in the healthy controls. Patients in clinical categories B/C with severe diseases were significantly more likely to have one variant allele. There was a statistical relationship between MBL2 genotypes and MBL serum levels. In addition, higher CD4(+) T cell counts and ratios of CD4(+) T cells:CD8(+) T cells were observed in patients with medium MBL levels than with low or high MBL levels. Patients with mild diseases were also more likely to have medium MBL levels than high levels. Analysis of MBL levels with respect to sex yielded differences. Median MBL levels were substantially higher in males than in females in HIV-1-infected patients. Lower CD4(+) T cell counts were detected in males with low MBL levels, but the opposite was observed in females. Our results suggest that genetic polymorphisms resulting in MBL deficiency are associated with increased susceptibility to HIV-1 infection and disease progression in the studied population. Moreover, serum circulating levels of normal MBL in HIV-1-infected patients could be an important auxiliary biological marker in association with CD4(+) T cell counts in the evaluation of HIV-1 disease progression. The sex differences in the regulation of MBL serum levels during infection merit further exploration.

A novel measurement method for activation of the lectin complement pathway via both mannose-binding lectin (MBL) and L-ficolin

Mannose-binding lectin (MBL), L-ficolin and H-ficolin are human serum lectins, all of which form complexes with MBL-associated serine proteases (MASP). The lectin-MASP complexes bind to the surface of microbes, leading to activation of the lectin pathway of complement. Enzyme-linked immunosorbent assays (ELISA) of the lectin pathway activity reported so far determined the activity via either MBL or L-ficolin, but an assay of activity via plural host defense lectins has not been established. To measure the lectin pathway activation mediated by plural lectins simultaneously, we developed an ELISA system in which N-acetylglucosamine-pentamer conjugated to dipalmitoylphosphatidylethanolamine (GN5-DPPE) was employed as a ligand for the lectins. In our ELISA system, both purified MBL and L-ficolin isolated from serum diluted in a buffer containing high ionic NaCl bound to GN5-DPPE and activated C4. Purified H-ficolin was not capable of binding to GN5-DPPE. MBL and L-ficolin in MBL-sufficient serum also bound to GN5-DPPE and activated C4. Mannose and N-acetylgalactosamine inhibited binding of MBL and L-ficolin to GN5-DPPE, respectively. MBL-deficient serum that had been depleted of L-ficolin did not exhibit C4 activation, but addition of both or either purified MBL and/or L-ficolin to the serum restored the activation in a dose-dependent manner. Thus, C4 cleaving activity could be evaluated with the co-existence of MBL and L-ficolin in vitro. In conclusion, we propose a novel method using GN5-DPPE for investigating the MBL- and L-ficolin-dependent lectin pathway and anticipate that this method will be useful in innate immunity and clinical research.

Paths reunited: Initiation of the classical and lectin pathways of complement activation

Understanding the structural organisation and mode of action of the initiating complex of the classical pathway of complement activation (C1) has been a central goal in complement biology since its isolation almost 50 years ago. Nevertheless, knowledge is still incomplete, especially with regard to the interactions between its subcomponents C1q, C1r and C1s that trigger activation upon binding to a microbial target. Recent studies have provided new insights into these interactions, and have revealed unexpected parallels with initiating complexes of the lectin pathway of complement: MBL-MASP and ficolin-MASP. Here, we develop and expand these concepts and delineate their implications towards the key aspects of complement activation via the classical and lectin pathways.

MBL2, FCN1, FCN2 and FCN3-The genes behind the initiation of the lectin pathway of complement

Mannose-binding lectin (MBL) and the ficolins (Ficolin-1, Ficolin-2 and Ficolin-3) are soluble collagen-like proteins that are involved in innate immune defence. They bind sugar structures or acetylated compounds present on microorganisms and on dying host cells and they initiate activation of the lectin complement pathway in varying degrees. Common variant alleles situated both in promoter and structural regions of the human MBL gene (MBL2) influence the stability and the serum concentration of the protein. Although not as thoroughly investigated as the MBL2 gene polymorphisms the ficolin genes (FCNs) also exhibit genetic variations affecting both the serum concentration, stability and binding capacity of the corresponding proteins. Epidemiological studies have suggested that the genetically determined variations in MBL serum concentrations influence the susceptibility to and the course of different types of diseases, while the importance of the ficolins in general and the genetic variation in the FCNs genes in particular is still largely unresolved. This overview will summarize the current molecular knowledge of the human MBL2, FCN1, FCN2 and FCN3 genes.

Interactions of ficolin and mannose-binding lectin with fibrinogen/fibrin augment the lectin complement pathway

Ficolin and mannose-binding lectin (MBL) are animal lectins that are involved in innate immunity by initiating the lectin complement pathway. Here, we report that interactions between these lectins and fibrinogen/fibrin augment the lectin pathway. An ELISA revealed that recombinant mouse ficolin A (rFcnA), rMBL-A and rMBL-C bind to fibrinogen in a dose-dependent manner. Affinity Western blotting showed that these lectins bind to the A alpha- and B beta-chains of fibrinogen and the alpha- and beta-chains of fibrin, but not to the gamma-chain, and that rMBL-A and rMBL-C preferentially bind to the alpha- and beta-chains. The C4 deposition activity on Fbg-coated plates was observed by using mouse serum, and the deposition on GlcNAc-coated plates was enhanced by fibrinogen supplementation and further enhanced by the addition of thrombin. Similar effects of fibrinogen and fibrin were observed in the bindings of these lectins to a Gram-positive pathogen, Staphylococcus aureus, and in the subsequent C3 deposition on the bacteria. In particular, the lectin pathway, through MBLs, seemed to synchronize with blood coagulation. Therefore, it is suggested that the lectin pathway collaborates with the coagulation system in the first-line host defense against pathogens under conditions such as injury and inflammation.

Two factors of the lectin pathway of complement, l-ficolin and mannan-binding lectin, and their associations with prematurity, low birthweight and infections in a large cohort of Polish neonates

Ficolins and one collectin, mannan-binding lectin (MBL), are the only factors known to activate the lectin pathway (LP) of complement. There is considerable circumstantial evidence that MBL insufficiency can increase susceptibility to various infections and influence the course of several non-infectious diseases complicated by infections. Much less information is available concerning l-ficolin. We report the results of a prospective study to investigate any association between either MBL deficiency or l-ficolin deficiency with prematurity, low birthweight or perinatal infections in a large cohort of Polish neonates, representing an ethnically homogenous population (n=1832). Cord blood samples were analysed to determine mbl-2 gene variants, MBL concentrations and MBL-MASP-2 complex activities (MBL-dependent lectin pathway activity) as well as l-ficolin levels. Median concentrations of l-ficolin and MBL were 2500 and 1124 ng/ml, respectively, while median LP activity was 272 mU/ml. After genotyping, 60.6% of babies were mbl-2 A/A, 35.4% were A/O and 4% were O/O genotypes. We found relative l-ficolin deficiency to be associated with prematurity, low birthweight and infections. l-Ficolin concentration correlated with gestational age and with birthweight, independently of gestational age. Preterm deliveries (<38 weeks) occurred more frequently among neonates with low LP activity but not with those having low serum MBL levels. Similarly, no association of serum MBL deficiency with low birthweight was found, but there was a correlation between LP activity and birthweight. Genotypes conferring very low serum MBL concentrations were associated with perinatal infections, and high-MBL-conferring genotypes were associated with prematurity. Our findings suggest that l-ficolin participates in host defence during the perinatal period and constitute the first evidence that relative l-ficolin deficiency may contribute to the adverse consequences of prematurity. Some similar trends were found with facets of MBL deficiency, but the observed relationships were weaker and less consistent.

Humoral pattern recognition molecules: mannan-binding lectin and ficolins

Innate immunity comprises a sophisticated network of molecules, which recognize pathogens, and effector molecules, working together to establish a quick and efficient immune response to infectious agents. Complement activation triggered by mannan binding lectin (MBL) or ficolins represents a beautiful example of this network Both MBL and ficolins recognize specific chemical structures on the surface of antigens and pathogens, thus bind to a broad variety of pathogens. Once bound further complement deposition is achieved through a cascade of proteolytic reactions. MBL and ficolin induced complement activation is critical for adequate anti-bacterial, anti-fungal and anti-viral responses. This is well illustrated by numerous and convincing studies that demonstrate associations between MBL deficiency and infections. Recent work has also highlighted that MBL and ficolins recognize self-structures, thus extending the role of these molecules beyond the traditional view of first line defense molecules. It appears that MBL deficiency may modulate the prognosis of inflammatory and autoimmune diseases. What is known about the mechanisms behind this broad scope of activities of MBL and ficolins is discussed in this chapter.

Deficiency of mannose-binding lectin greatly increases antibody response in a mouse model of vaccination

Mannose-binding lectin (MBL), a pattern recognition innate immune molecule, selectively binds distinct chemical patterns, including carbohydrates expressed on Group B streptococcus (GBS). MBL interacts with IgM, resulting in the activation of MBL-associated serine proteases (MASPs), thus is initiating a lectin complement pathway. Complement proteins and IgM modulate production of antigen specific antibody. In this study, we investigated the relative effect of MBL in antibody response against tetanus toxoid-conjugated GBS polysaccharide vaccines (GBS PS-TT) by comparing wild type and null mice for MBL, complement 3 (C3), IgM, MBL/C3, and MBL/IgM. We found that GBS PS specific IgG response was upregulated in MBL deficient mice following immunization with GBS PS-TT but not GBS PS. B1 cells were expanded in peritonium but not in spleen of MBL null mice. The mechanisms of heightened IgG response in MBL null mice were related to C3, and share the same pathway with IgM.

Mannan-binding lectin (MBL) in two chicken breeds and the correlation with experimental Pasteurella multocida infection

The present study is the first demonstration of an association of the genetic serum Mannan-binding lectin (MBL) concentration with bacterial infections in chickens. The genetic serum MBL concentration was determined in two chicken breeds, and the association with the specific Pasteurella multocida humoral immune response during an experimental infection was examined. Furthermore, we examined the association of the genetic serum MBL concentration with systemic infection. The chickens with systemic infection had a statistically significant lower mean serum MBL concentration than the rest of the chickens, suggesting that MBL plays an important role against P. multocida. A statistically significant negative correlation was found between the specific antibody response and the genetic serum MBL concentration for both breeds. This indicates that MBL in chickens is capable of acting as the first line of defence against P. multocida by diminishing the infection before the adaptive immune response takes over.

Disease associations of mannose-binding lectin & potential of replacement therapy

Mannose-binding lectin (MBL) is an important component of the immune defence able to bind to repeating mannose based structural patterns typical of microbial surface (bacteria, viruses, fungi, parasites) leading to opsonization and phagocytosis, and activation of the complement pathway resulting in lysis of the pathogen. MBL thus plays a very important role in the first line of host immune response. MBL deficiency has been implicated in susceptibility and modulating the severity in viral, bacterial, fungal, and protozoan infections. High MBL levels, on the contrary might be helpful to intracellular organisms, which take the advantage of C3 opsonization and C3 receptor on monocytes/macrophages to enter their host. MBL replacement therapy to help patients with MBL deficiency has undergone phase I clinical trials. Phase II and III trials and production of recombinant MBL for replacement therapy are currently underway.

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).

Ficolins: structure, function and associated diseases

Innate immunity relies upon the ability of a few pattern recognition molecules to sense molecular markers. Ficolins are humoral molecules of the innate immune systems which recognize carbohydrate molecules on pathogens, apoptotic and necrotic cells. Three ficolins have been identified in humans: L-ficolin, H-ficolin and M-ficolin (also referred to as ficolin-2, -3 and -1, respectively). They are soluble oligomeric defence proteins with lectin-like activity and they are structurally similar to the human collectins, mannan-binding lectin (MBL) and surfactant protein A and D. Upon recognition of the infectious agent, the ficolins act through two distinct routes: initiate the lectin pathway of complement activation through attached serine proteases (MASPs), and a primitive opsonophagocytosis thus limiting the infection and concurrently orchestrating the subsequent adaptive clonal immune response. Recently a lot of reports showed that dysfunction or abnormal expressions of ficolins may play crucial roles in the pathogenesis of human diseases including: (1) infectious and inflammatory diseases, e.g., recurrent respiratory infections; (2) apoptosis, and autoimmune disease; (3) systemic lupus erythematosus; (4) IgA nephropathy; (5) clinical syndrome of preeclampsia; (6) other diseases associated factor e.g. C-reactive protein. Precise identification of ficolins functions will provide novel insight in the pathogenesis of these diseases and may provide novel innate immune therapeutic options to treat disease progression. This review discusses the structures, functions, and clinical implications of ficolins and summarizes the reports on the roles of ficolins in human diseases.

Biological variation in circulating levels of mannan-binding lectin (MBL) and MBL-associated serine protease-2 and the influence of age, gender and physical exercise

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) are central components of the MBL pathway of complement activation, and may have potential as clinical biomarkers in colorectal cancer (CRC). Prior to clinical usage, knowledge of the biological variations of the molecules is needed. We here investigate variations of MBL and MASP-2 in healthy persons over time and in relation to gender, age and physical activity. MBL and MASP-2 concentrations were determined in serum from healthy adults over a 3-week period and this was repeated 6 months later (n = 32); during a 24-h period (n = 16); and in relation to physical exercise (n = 14). Concentrations in serum and plasma were compared (n = 198). No significant variation over 6 months and no circadian variation was found for MBL (P = 0.39 and P = 0.34 respectively) or MASP-2 (P = 0.54 and P = 0.55). Physical exercise did not affect the levels (P > 0.8). Serum and plasma levels were only marginally different, and were independent of age and gender. Circulating levels of MBL and MASP-2 are stable over time in healthy individuals, which is advantageous for their potential application as biomarkers.

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.

Complement activating soluble pattern recognition molecules with collagen-like regions, mannan-binding lectin, ficolins and associated proteins

Mannan-binding lectin (MBL), L-ficolin, M-ficolin and H-ficolin are all complement activating soluble pattern recognition molecules with recognition domains linked to collagen-like regions. All four may form complexes with four structurally related proteins, the three MBL-associated serine proteases (MASPs), MASP-1, MASP-2 and MASP-3, and a smaller MBL-associated protein (MAp19). The four recognition molecules recognize patterns of carbohydrate or acetyl-group containing ligands. After binding to the relevant targets all four are able to activate the complement system. We thus have a system where four different and/or overlapping patterns of microbial origin or patterns of altered-self may be recognized, but in all cases the signalling molecules, the MASPs, are shared. MASP-1 and MASP-3 are formed from one gene, MASP1/3, by alternative splicing generating two different mRNAs from a single primary transcript. Similarly MASP-2 and MAp19 are both generated from one gene, MASP-2/MAp19, by alternative splicing. A number of non-synonymous polymorphisms of the four recognition molecules and of the MASPs are known, and the implications of these alterations are being studied. The clinical impact of deficiencies will be discussed.