Lectin pathway of complement activation and relation with clinical complications in critically ill children

BACKGROUND

Critically ill children are susceptible to nosocomial infections, which contribute to adverse outcomes. Deficiencies in the innate immunity lectin pathway of complement activation are implicated in a child's vulnerability to infections in conditions such as cancer, but the role during critical illness remains unclear. We hypothesized that low on-admission levels of the pathway proteins are, in part, genetically determined and associated with susceptibility to infectious complications and adverse outcomes.

METHODS

We studied protein levels of mannose-binding lectin (MBL), H-ficolin and M-ficolin, three MBL-associated-serine proteases (MASPs) and MBL-associated protein (MAp44), and relation with functional genetic polymorphisms, in 130 healthy children and upon intensive care unit (ICU) admission in 700 critically ill children of a randomized study on glycemic control.

RESULTS

Levels of MASP-1, MASP-2, MASP-3, and MAp-44 were lower and the levels of M-ficolin were higher in ICU patients on admission than those in matched healthy controls. Only a low on-admission MASP-3 level was independently associated with risk of new ICU infections and prolonged ICU stay, after correcting for other risk factors. On-admission MASP-3 varied with age, illness severity, and genetic variation.

CONCLUSION

Low on-admission MASP-3 levels in critically ill children were independently associated with subsequent acquisition of infection and prolonged ICU stay. The biological explanation needs further investigation.

Polymorphisms in the MASP1 gene are associated with serum levels of MASP-1, MASP-3, and MAp44

INTRODUCTION

MASP-1 is the first protein in the activation of the lectin pathway and MASP-1 is, like its isoforms MASP-3 and MAp44, encoded by the MASP1 gene. Our aim was to explore associations between polymorphisms in MASP1 and corresponding concentrations of MASP-1, MASP-3, and MAp44 in plasma as well as the genetic contribution to the equilibrium between the three proteins.

METHODS

Fifteen SNPs were genotyped in the MASP1 gene in 350 blood donors. Corresponding plasma concentrations of MASP-1, MASP-3, and MAp44 were measured.

RESULTS

A total of 10 different SNPs showed associations with the concentration of one or some of the three proteins (rs113938200, rs190590338, rs35089177, rs3774275, rs67143992, rs698090, rs72549154, rs72549254, rs75284004, rs7625133), and several of these were in strong linkage. SNPs located in the mutually exclusive splice region had opposite effects on the protein concentrations. Being e.g. homozygote for the minor allele of rs3774275 was associated with an increase in median concentration of 13% in MASP-1(P=0.03), 29% in MAp44 (P<0.001), and a decrease in MASP-3 of 26% (P<0.001) compared to homozygosis for the major allele. Heterozygosis of rs113938200 (p.Asn368Asp in MAp44) was associated with a reduced MAp44 concentration of 61% (P=0.005). Rs190590338 located in the promoter region was associated in the heterozygote form with an increased MASP-1 concentration of 35% (P = 0.002). A multivariate linear regression model including sex, age, M- and H-ficolin, MBL, and the 15 SNPs explained 20-48% of the variation in the concentration of the three proteins and the SNPs investigated contributed with the most explanatory power (12-23%).

DISCUSSION

The present study described 10 SNPs, which were associated with the concentration of one or some of the three proteins originating from the MASP1 gene and in a multivariate model it was shown that the SNPs contributed with the most explanatory power to the protein concentrations.

Plasma TNF-α levels are higher in early pregnancy in patients with secondary compared with primary recurrent miscarriage

PROBLEM

Specific pro-inflammatory cytokine profiles in plasma may characterize women with recurrent miscarriage (RM) but the dynamics of the cytokine profiles with progressing pregnancy is largely unknown.

METHOD OF STUDY

Plasma was repeatedly sampled in the first trimester from 47 RM patients. The concentrations of five cytokines including tumour necrosis factor alpha (TNF-α) were measured. TNF-α levels were correlated to carriage of five TNFA promoter polymorphisms.

RESULTS

TNF-α levels increased (P = 0.014) with progressing pregnancy, with higher levels in secondary than primary RM (P = 0.042) but with no significant impact on outcome. Carriage of TNFA -863C and TNFA -1031T was associated with higher TNF-α levels, and the former was found more often in secondary than primary RM (P < 0.02).

CONCLUSION

Plasma TNF-α levels increase during early pregnancy in RM women regardless of outcome, but are higher in secondary than primary RM, which may be partly genetically determined.

A modest but significant effect of CGB5 gene promoter polymorphisms in modulating the risk of recurrent miscarriage

Objective

To confirm the effect of single nucleotide polymorphisms (SNPs) in chorionic gonadotropin beta (CGB) genes in modulating the susceptibility to recurrent miscarriage (RM) in Danes and in a meta-analysis across Danes and the discovery samples from Estonia and Finland.

Design

Case-control association study, restriction fragment length polymorphism genotyping, resequencing.

Setting

Fertility clinics at the Rigshospitalet, Copenhagen, and Aalborg Hospital, Aalborg, Denmark.

Patient(s)

Four hundred fifty Danish women and men from couples with RM and 119 women with children and no miscarriages in new study. A total of 634 women and men from RM couples and 314 female controls in a combined study of Estonians, Finns, and Danes.

Intervention(s)

None.

Main Outcome Measure(s)

Distribution of CGB5 and CGB8 allele and haplotype frequencies in patients and controls.

Result(s)

For the majority of studied SNPs, the allelic and haplotypic distribution differed statistically between the Danish and the previous Estonian-Finnish sample. In Danes, two CGB5 promoter SNPs (c5-155; c5-142) exhibited a nonsignificant trend for higher allele frequency in fertile women compared with RM patients. The meta-analysis of results from three populations confirmed a modest but significant effect on carriage of c5-155C (odds ratio = 0.64; 95% confidence interval [CI] 0.44–0.94) and c5-142A (odds ratio = 0.66; 95% CI, 0.45–0.94) variants in reducing the risk of RM. None of the investigated genetic variants in the CGB8 gene was associated with RM.

Conclusion(s)

Carriage of particular variants in the promoter of the CGB5 gene seems to protect against RM. No common genetic variants in CGB5 and CGB8 were associated with increased RM susceptibility in the studied North European populations.

Susceptibility to leprosy is associated with M-ficolin polymorphisms

PURPOSE

Mycobacterium leprae exploits complement activation and opsonophagocytosis to infect phagocytes. M-ficolin is encoded by the FCN1 gene and initiates the lectin pathway on monocyte surfaces. We investigated FCN1 promoter polymorphisms that could be responsible for the high interindividual variability of M-ficolin levels and for modulating leprosy susceptibility.

METHODS

We genotyped rs2989727 (-1981 G > A), rs28909068 (-791 G > A), rs10120023 (-542 G > A), rs17039495 (-399 G > A), rs28909976 (-271IndelT), rs10117466 (-144C > A) and rs10858293 (+33 T > G) in 400 controls and 315 leprosy patients from Southern Brazil, and in 296 Danish healthy individuals with known M-ficolin levels.

RESULTS

Ten haplotypes were identified with sequence-specific PCR and/or haplotype-specific sequencing. We found evidence for a protective codominant additive effect of FCN1*-542A-144C with leprosy in Euro-Brazilians (P=0.003, PBf =0.021, OR=0.243 [CI95% =0.083-0.71]), which was independent of age, ethnic group and gender effects (P=0.029). There was a trend for a positive association of the -399A variant in Afro-Brazilians (P=0.022, PBf =0.154, OR=4.151 [CI95% =1.115-15.454], as well as for a negative association of the FCN1*3A haplotype with lepromatous leprosy, compared with less severe forms of the disease (P=0.016, PBf =0.112, OR=0.324 [CI95% =0.123-0.858]). Danish individuals with this haplotype presented M-ficolin levels higher than the population average of circa 1,000 ng/ml, and -542A-144C, which is able to modify the recognition of transcription factors in silico, occurred in individuals with levels under the 25 percentil (P=0.031).

CONCLUSIONS

Our data provide the first evidence that FCN1 polymorphisms are associated with leprosy. M-ficolin may represent a novel key to understand the immunopathogenesis of M. leprae infection.

Non-synonymous polymorphisms in the FCN1 gene determine ligand-binding ability and serum levels of M-ficolin

BACKGROUND

The innate immune system encompasses various recognition molecules able to sense both exogenous and endogenous danger signals arising from pathogens or damaged host cells. One such pattern-recognition molecule is M-ficolin, which is capable of activating the complement system through the lectin pathway. The lectin pathway is multifaceted with activities spanning from complement activation to coagulation, autoimmunity, ischemia-reperfusion injury and embryogenesis. Our aim was to explore associations between SNPs in FCN1, encoding M-ficolin and corresponding protein concentrations, and the impact of non-synonymous SNPs on protein function.

PRINCIPAL FINDINGS

We genotyped 26 polymorphisms in the FCN1 gene and found 8 of these to be associated with M-ficolin levels in a cohort of 346 blood donors. Four of those polymorphisms were located in the promoter region and exon 1 and were in high linkage disequilibrium (r(2)≥0.91). The most significant of those were the AA genotype of -144C>A (rs10117466), which was associated with an increase in M-ficolin concentration of 26% compared to the CC genotype. We created recombinant proteins corresponding to the five non-synonymous mutations encountered and found that the Ser268Pro (rs150625869) mutation lead to loss of M-ficolin production. This was backed up by clinical observations, indicating that an individual homozygote of Ser268Pro would be completely M-ficolin deficient. Furthermore, the Ala218Thr (rs148649884) and Asn289Ser (rs138055828) were both associated with low M-ficolin levels, and the mutations crippled the ligand-binding capability of the recombinant M-ficolin, as indicated by the low binding to Group B Streptococcus.

SIGNIFICANCE

Overall, our study interlinks the genotype and phenotype relationship concerning polymorphisms in FCN1 and corresponding concentrations and biological functions of M-ficolin. The elucidations of these associations provide information for future genetic studies in the lectin pathway and complement system.

Prognosis by C-reactive protein and matrix metalloproteinase-9 levels in stable coronary heart disease during 15 years of follow-up

BACKGROUND AND AIM

Elevated CRP and matrix metalloproteinase-9 associate with increased risk of cardiovascular events, possibly because these plasma proteins mark vulnerable atherosclerotic plaques. We tested the hypothesis that levels of C-reactive protein (CRP) and matrix metalloproteinase-9 associate with prognosis in patients with stable coronary heart disease.

METHODS AND RESULTS

We measured baseline plasma CRP and matrix metalloproteinase-9 in 1090 patients with stable coronary heart disease and as the primary composite endpoint detected incident unstable angina, myocardial infarction and any death during 15 years of follow-up. CRP above versus below the median of 3.0 mg/L was associated with an increased cumulative incidence of unstable angina, myocardial infarction and any death combined (log-rank p < 0.0001). CRP above versus below the median had a corresponding hazard ratio of 1.5(95% CI, 1.3-1.8) after age adjustment, of 1.4(1.2-1.6) after multifactorial adjustment, and of 1.4(1.2-1.6) after multifactorial adjustment including degree of coronary disease. In contrast, matrix metalloproteinase-9 above versus below the median was not associated with risk of unstable angina, myocardial infarction and death.

CONCLUSIONS

Elevated CRP, but not elevated matrix metalloproteinase-9, associates with increased risk of unstable angina, myocardial infarction and death in patients with stable coronary heart disease.

Structural and functional analysis of rare missense mutations in human chorionic gonadotrophin β-subunit

Heterodimeric hCG is one of the key hormones determining early pregnancy success. We have previously identified rare missense mutations in hCGβ genes with potential pathophysiological importance. The present study assessed the impact of these mutations on the structure and function of hCG by applying a combination of in silico (sequence and structure analysis, molecular dynamics) and in vitro (co-immunoprecipitation, immuno- and bioassays) approaches. The carrier status of each mutation was determined for 1086 North-Europeans [655 patients with recurrent miscarriage (RM)/431 healthy controls from Estonia, Finland and Denmark] using PCR-restriction fragment length polymorphism. The mutation CGB5 p.Val56Leu (rs72556325) was identified in a single heterozygous RM patient and caused a structural hindrance in the formation of the hCGα/β dimer. Although the amount of the mutant hCGβ assembled into secreted intact hCG was only 10% compared with the wild-type, a stronger signaling response was triggered upon binding to its receptor, thus compensating the effect of poor dimerization. The mutation CGB8 p.Pro73Arg (rs72556345) was found in five heterozygotes (three RM cases and two control individuals) and was inherited by two of seven studied live born children. The mutation caused ∼50% of secreted β-subunits to acquire an alternative conformation, but did not affect its biological activity. For the CGB8 p.Arg8Trp (rs72556341) substitution, the applied in vitro methods revealed no alterations in the assembly of intact hCG as also supported by an in silico analysis. In summary, the accumulated data indicate that only mutations with neutral or mild functional consequences might be tolerated in the major hCGβ genes CGB5 and CGB8.

MAp19, the alternative splice product of the MASP2 gene

The lectin pathway of complement is a central part of innate immunity, but as a powerful inducer of inflammation it needs to be tightly controlled. The MASP2 gene encodes two proteins, MASP-2 and MAp19. MASP-2 is the serine protease responsible for lectin pathway activation. The smaller alternative splice product, MAp19, lacks a catalytic domain but retains two of three domains involved in association with the pattern-recognition molecules (PRMs): mannan-binding lectin (MBL), H-ficolin, L-ficolin and M-ficolin. MAp19 reportedly acts as a competitive inhibitor of MASP-2-mediated complement activation. In light of a ten times lower affinity of MAp19, versus MASP-2, for association with the PRMs, much higher serum concentrations of MAp19 than MASP-2 would be required for MAp19 to exert such an inhibitory activity. Just four amino acid residues distinguish MAp19 from MASP-2, and these are conserved between man, mouse and rat. Nonetheless we generated monoclonal rat anti-MAp19 antibodies and established a quantitative assay. We found the concentration of MAp19 in serum to be 217 ng/ml, i.e., 11nM, comparable to the 7 nM of MASP-2. In serum all MASP-2, but only a minor fraction of MAp19, was associated with PRMs. In contrast to previous reports we found that MAp19 could not compete with MASP-2 for binding to MBL, nor could it inhibit MASP-2-mediated complement activation. Immunohistochemical analyses combined with qRT-PCR revealed that both MAp19 and MASP-2 were mainly expressed in hepatocytes. High levels of MAp19 were found in urine, where MASP-2 was absent.

Promoter polymorphisms in the chitinase 3-like 1 gene influence the serum concentration of YKL-40 in Danish patients with rheumatoid arthritis and in healthy subjects

Introduction

The present study investigates the association between single nucleotide polymorphisms (SNPs) in the chitinase 3-like 1 (CHI3L1) gene and serum concentrations of YKL-40 in Danish patients with rheumatoid arthritis (RA) and healthy controls as well as the association with RA in the Danish population. The CHI3L1 gene is located on chromosome 1q32.1 and encodes the YKL-40 glycoprotein. YKL-40 concentrations are elevated in the serum of patients with RA compared to healthy subjects, and YKL-40 has been suggested to be an auto-antigen and may play a role in development of RA and in inflammation.

Methods

Eight SNPs in the CHI3L1 gene and promotor were genotyped in 308 patients with RA and 605 controls (healthy blood donors) using TaqMan allele discrimination assays. Serum concentrations of YKL-40 were determined by an enzyme-linked immunosorbent assay (ELISA).

Results

We found significant association between the serum concentrations of YKL-40 and polymorphism in the CHI3L1 gene among both patients with RA and controls. The g.-131(C > G) polymorphism (rs4950928) was most strongly associated with age adjusted serum concentrations of YKL-40 in patients with RA (P < 2.4e-8) and controls (P < 2.2e-16). No significant allelic- or genotypic association with RA was found in this Danish cohort.

Conclusions

We suggest that the g.-131(C > G) promoter polymorphism has a substantial impact on serum concentrations of YKL-40 in patients with RA and healthy subjects. However, the polymorphism does not seem to confer risk to RA itself. The effect of CHI3L1 polymorphism on clinical outcome or the response to treatment in patients with RA remains to be investigated.

The presence of HLA-antibodies in recurrent miscarriage patients is associated with a reduced chance of a live birth

Anti-paternal HLA-antibodies are considered a harmless phenomenon during most pregnancies, whereas their role in recurrent miscarriage (RM) patients is disputed. In contrast to primary RM, patients with secondary RM have carried a fetus to term pregnancy prior to a series of miscarriages, which increases the chance that allogeneic fetal cells appear in the maternal circulation. This study investigates the frequency of HLA-antibodies in secondary RM, primary RM patients and parous controls and analyzes whether the presence of HLA-antibodies in early pregnancy is associated with pregnancy outcome. Sera from women with secondary RM (n=56), primary RM (n=13) and parous controls (n=24) were tested for HLA-antibodies using an ELISA assay and complement dependent cytotoxicity. Samples were taken at gestational week 4-5 in 62 (90%) of the patients. HLA-antibodies were significantly more frequent in secondary RM patients with a boy prior to the miscarriages (62%) compared to secondary RM patients with a firstborn girl (29%, p=0.03), primary RM patients (23%, p=0.02) and parous controls (25%, p=0.005). Forty-one percent of HLA-antibody positive pregnant RM patients had a live birth compared to 76% of HLA-antibody negative RM patients, p=0.006 (adjusted OR: 0.22 (0.07-0.68), p=0.008). In conclusion, HLA-antibodies are significantly more frequent in secondary RM patients with a firstborn boy than in other RM patients and controls. The presence of these antibodies in early pregnancy is associated with a reduced chance of a live birth. Further exploring this association may increase our understanding of maternal acceptance of the fetal allograft.

Complement Factor MASP-2 is activated after acute myocardial ischemia in human (116.28)

Acute blockage of coronary artery results in myocardial injury manifested in clinical situations such as myocardial infarction (MI). Following ischemia, inflammation is provoked and may be related to the clinical outcomes. We studied the acute inflammatory response immediately following myocardial ischemia in human. Our results showed that in acute MI patients circulation levels of complement factor MASP-2 were significantly reduced comparing with those of healthy individuals or of coronary artery disease (CAD) patients without acute MI. This reduction was not due to genetic polymorphism of MASP-2 in acute MI patients. We hypothesized that MASP-2 was activated after acute myocardial ischemia, and tested this in cardiac patients undergoing surgically induced transient global heart ischemia. Our results showed that MASP-2 was significantly reduced in coronary circulation after global heart ischemia and was independently correlated with the post-operative increase of the myocardial injury marker, cardiac Troponin I. These data suggested that MASP-2 is activated in human acute heart ischemia and associated with myocardial injury.

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) genotypes in colorectal cancer

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) are key factors of the lectin pathway of complement activation. Polymorphisms of the MBL2 and MASP-2 genes affect serum levels of MBL and MASP-2. In patients with colorectal cancer (CRC), the MBL and MASP-2 serum levels are increased and high MASP-2 levels are associated with recurrence and poor survival, whereas low MBL levels predict post-operative pneumonia. It is not known whether these associations are genetically based. In this study, the MBL and MASP-2 genotypes are investigated in 593 patients with CRC and 348 healthy controls. The potential association between genetic profile and infections, recurrence and survival is evaluated. Four single-nucleotide polymorphisms (SNPs) of MBL2 were analysed using TaqMan assays, with characterization of MBL2 wildtype A, variants B, C and D and alleles H/L, Y/X and P/Q. The SNP D120G for MASP-2 was determined. Serum levels of MBL and MASP-2 were measured. The MBL2 and MASP-2 genotype distribution was similar among patients with CRC and healthy controls and MBL2 genotype significantly associated with MBL concentration in serum (P<0.0001). No significant association between MBL2/MASP-2 genotype and post-operative infectious complications (P=0.33 and 0.22), recurrent cancer or survival (P=0.74 and P=0.61 respectively) was found. Thus, the increased serum levels of MBL and MASP-2 found in patients with CRC are not explained for by genetic profiles. In contrast to what has been demonstrated for serum levels of MBL and MASP-2, the genotypes do not predict disease course of the CRC patients.

Mannose-binding lectin genotype and phenotype in patients with type 2 diabetes and myocardial infarction: a report from the DIGAMI 2 trial

OBJECTIVE

The present study characterizes mannose-binding lectin (MBL), an activator of the complement system and thereby important for inflammatory activation, in patients with diabetes and myocardial infarction.

RESEARCH DESIGN AND METHODS

Serum (S)-MBL was determined at hospital admission in 387 patients with type 2 diabetes (median age 70 years; 68% male) with myocardial infarction, and genotyping was performed in 287 patients. Cardiovascular events (cardiovascular mortality and nonfatal myocardial infarction or stroke) were recorded during 2.5 years.

RESULTS

Median S-MBL was 1,212 μg/l (interquartile range [IQR] 346-2,681 μg/l). Of the subjects, 54% in the geno- and phenotype subgroup had a high-coding MBL genotype (median S-MBL=2,658 μg/l [IQR 1,715-3,829]) and 46% a low-coding MBL genotype (373 μg/l [100-765]). S-MBL did not correlate with age, BMI, creatinine clearance, glucose, or A1C. Cardiovascular events occurred in 136 (35%) patients. S-MBL did not predict events in univariable analyses (hazard ratio 0.93 [95% CI 0.85-1.01]; P=0.09). In unadjusted analyses, the risk of events was lower in patients with a high genotype and S-MBL above the median for their genotype (0.49 [0.26-0.92]; P=0.026) than for patients with a low genotype and S-MBL below the median for their genotype. The prediction capacity of the geno- and phenotype model was of borderline significance in adjusted Cox regression.

CONCLUSIONS

Patients with type 2 diabetes and myocardial infarction have MBL genotypes that are similar to those known in the general population. The combination of a low-coding MBL genotype with a low S-MBL appears to be prognostically unfavorable, but the association is blunted by traditional risk markers.

Hereditary thrombophilia and recurrent pregnancy loss: a retrospective cohort study of pregnancy outcome and obstetric complications

BACKGROUND

The association among hereditary thrombophilia, recurrent pregnancy loss (RPL) and obstetric complications is yet uncertain. The objective of the study was to assess the prognostic value of the factor V Leiden (FVL) and prothrombin (PT) mutations for the subsequent chance of live birth for women with RPL.

METHODS

Pregnancy outcome was recorded in a retrospective cohort of 363 women with a minimum of three consecutive pregnancy losses (early miscarriage, late miscarriage or stillbirth/neonatal death) who were not treated with anticoagulation therapy.

RESULTS

Of the 363 women, 29 were FVL-mutation carriers and 6 were PT-mutation carriers. The unadjusted live birth rate was 45.7% in FVL/PT carriers versus 63.4% in FVL/PT non-carriers, P = 0.04. The adjusted odds ratio for live birth in FVL/PT carriers was 0.48 (95% CI = 0.23-1.01), P = 0.05. Among the obstetric complications, only excessive bleeding was found to be associated with FVL/PT mutations.

CONCLUSIONS

In the unadjusted analysis, FVL and PT mutations have a negative prognostic impact on the live birth rate in women with RPL; however, when adjusting for significant covariates, the results no longer reach statistical significance. Strong conclusions on the association between obstetric complications and hereditary thrombophilia cannot be drawn from this study. Whether anticoagulation therapy would improve the prognosis in women with RPL and FVL/PT mutations remains to be documented in large randomized controlled trials.

H-Y antibody titers are increased in unexplained secondary recurrent miscarriage patients and associated with low male : female ratio in subsequent live births

BACKGROUND

The birth of a boy is significantly more common than a girl prior to secondary recurrent miscarriage (SRM) and is associated with a poorer chance of a subsequent live birth. Children born after SRM are more likely to be girls. High-titer antisera specific for male antigens (H-Y) have been shown to arrest development of male bovine embryos efficiently. We consequently questioned the role of H-Y antibodies in women with SRM.

METHODS

Serum samples from patients with unexplained SRM (n = 84), unexplained primary recurrent miscarriage (PRM) (n = 12) and healthy women (n = 37) were obtained. The samples were taken during pregnancy (gestational weeks 4-5) for 77 (80%) of the patients. Enzyme-linked immunosorbent assay was used to detect immunoglobulin G antibodies that specifically recognized any of the five recombinant H-Y proteins (EIF1AY, RPS4Y1, ZFY, DDX3Y and UTY) and their H-X homologs.

RESULTS

H-Y-specific antibodies were more frequent in SRM patients (46%) compared with female controls (19%, P = 0.004) and PRM patients (8%, P = 0.01). The presence of H-Y antibodies in early pregnancy was associated with a low male: female birth ratio among the subsequent live births, as only 12% of children born to H-Y antibody-positive patients were boys compared with 44% boys born to H-Y antibody negative patients (P = 0.03).

CONCLUSIONS

The high frequency of H-Y antibody-positive SRM patients and the association between the presence of these antibodies in early pregnancy and the low number of male offspring, suggest that maternal immune responses against H-Y antigens can cause pregnancy losses. Further exploring these mechanisms may increase our understanding of unexplained SRM.

KEL*02 alleles with alterations in and around exon 8 in individuals with apparent KEL:1,-2 phenotypes

BACKGROUND AND OBJECTIVES

Antibodies to antigens in the Kell blood group system, especially anti-KEL1, are involved in both haemolytic disease of the newborn and foetus and haemolytic transfusion reactions. Correct typing results are important and discrepancies between serologic and genetic typing must be resolved. Here, we describe the investigation of three healthy individuals who were initially phenotyped as KEL:1,-2.

MATERIALS AND METHODS

Antigen typing was performed by standard serological techniques and by flow cytometric analysis. The KEL*01/02 polymorphism was tested by an allele-discrimination TaqMan assay as well as by PCR with allele-specific primers and PCR-RFLP. DNA sequencing of the KEL coding region was also performed.

RESULTS

Two KEL*02N alleles with mutated splice sites around exon 8 were identified: intron 7 -1g>c (novel) and intron 8 +1g>t (previously reported in one case of K(0)). In the third sample, a missense mutation in exon 8, 787G>A (novel) predicting Gly263Arg, was detected on a KEL*02 allele and associated with dramatically weakened KEL2 antigen expression.

CONCLUSION

Resolution of discrepant phenotype/genotype results identified silencing mutations in or around exon 8. A combination of molecular and serologic methods has the potential to improve the quality of test results and was required to ensure both the accurate KEL2 antigen status and KEL*01 zygosity of these individuals.

The impact of anti-HY responses on outcome in current and subsequent pregnancies of patients with recurrent pregnancy losses

Women pregnant with a male fetus often generate cellular and humoral immune responses against male-specific minor histocompatibility (HY) antigens-however, the importance of these responses for pregnancy outcome is unclear. Epidemiologic studies have shown that the birth of a boy compared with a girl prior to a series of miscarriages significantly reduces the chance of a subsequent live birth and pregnancies with boys have an increased risk of placental abruption. This paper aims to review the current knowledge about the impact of anti-HY immunity on pregnancy outcome in terms of miscarriage and placental abruption. Our knowledge primarily comes from studies of the impact on pregnancy outcome of HLA class II alleles known to restrict CD4 T cell mediated anti-HY responses among 358 secondary recurrent miscarriage (SRM) patients and 203 of their children born prior to the miscarriages and investigation of these HLA alleles in 8 patients with recurrent severe placental abruptions. The chance of a subsequent live birth in SRM patients with firstborn boys compared to firstborn girls was significantly lower in women with HY-restricting HLA class II alleles [OR: 0.17 (0.1-0.4), p=0.0001]. Most patients with recurrent placental abruptions had firstborn boys and significantly more of these patients carried HLA haplotypes with HY-restricting class II alleles compared with controls (p=0.009). These findings are strongly indicative of aberrant maternal immune reactions against fetal HY antigens playing a role in recurrent miscarriage and placental abruption. We propose pathogenetic pathways for these conditions that in our view best explain the findings.

Sepsis in acute myeloid leukaemia patients receiving high-dose chemotherapy: no impact of chitotriosidase and mannose-binding lectin polymorphisms

Infections after chemotherapy often cause significant morbidity in patients with acute myeloid leukaemia (AML). Chitotriosidase (CHIT) and mannose-binding lectin (MBL) are part of the innate immune system. Polymorphism in the CHIT-coding gene (CHIT1) may be associated with Gram-negative sepsis in children with AML, and polymorphism in the MBL-coding gene (MBL2) seems to modify the risk of infections in several patient groups. The purpose of this study was to investigate the possible associations between polymorphisms in CHIT1, MBL2 and sepsis in adult patients treated with high-dose chemotherapy for AML. We included 190 patients treated with 526 cycles of chemotherapy. The follow-up period was 6 months from the diagnosis of AML. Prophylactic antibiotics were not used. We identified 604 febrile episodes with 246 episodes of sepsis. Thirty-two patients (17%) either died from infection or infection was a major concomitant factor for death. No significant associations between CHIT1 polymorphism and sepsis (P = 0.85) or death caused by sepsis (P = 0.14) were found. Furthermore, no significant associations between MBL2 polymorphism and sepsis (P = 0.76) or death caused by sepsis (P = 0.24) were observed. The severe and long-lasting neutropenia and mucositis after chemotherapy may explain why the MBL system does not protect against sepsis in patients with AML. Replacement therapy with recombinant MBL is not likely to decrease the risk of sepsis in patients with AML.

Study of the structure and impact of human leukocyte antigen (HLA)-G-A, HLA-G-B, and HLA-G-DRB1 haplotypes in families with recurrent miscarriage

A 14-base pair (bp) long insertion (ins)/deletion (del) polymorphism in exon 8 in the 3'-untranslated region of the human leukocyte antigen (HLA)-G gene is suggested to affect transcription of the gene. Carriage of the G14bp ins is associated with low levels of soluble HLA-G and increases the risk of recurrent miscarriage (RM). Due to existence of strong linkage disequilibrium (LD) in the HLA region, the primary susceptibility genes for RM in the HLA-G region have not yet been identified. HLA-A, -B, -DRB1, and -G14bp polymorphisms were investigated in 29 Caucasian families with two or more siblings suffering unexplained RM. Strong positive LD was detected between the G14bp ins and HLA-A*01, -A*11, -A*31, -B*08, and DRB1*03, whereas strong negative LD was found between G14bp ins and HLA-A*02, -A*03, and -A*24. The frequency of haplotypes with HLA-G14bp ins inherited from the mother was significantly increased in probands with RM (p = 0.05). The increased compatibility between probands and their mothers for maternal G14 ins positive haplotypes suggests that maternal-fetal compatibility for chromosomal segments adjacent to HLA-G locus is a risk factor for female offspring to experience RM in their later reproductive life.

MAp44, a human protein associated with pattern recognition molecules of the complement system and regulating the lectin pathway of complement activation

Essential effector functions of innate immunity are mediated by complement activation initiated by soluble pattern recognition molecules: mannan-binding lectin (MBL) and the ficolins. We present a novel, phylogenetically conserved protein, MAp44, which is found in human serum at 1.4 microg/ml in Ca(2+)-dependent complexes with the soluble pattern recognition molecules. The affinity for MBL is in the nanomolar range (K(D) = 0.6 nM) as determined by surface plasmon resonance. The first eight exons of the gene for MAp44 encode four domains shared with MBL-associated serine protease (MASP)-1 and MASP-3 (CUB1-EGF-CUB2-CCP1), and a ninth exon encodes C-terminal 17 aa unique to MAp44. mRNA profiling in human tissues shows high expression in the heart. MAp44 competes with MASP-2 for binding to MBL and ficolins, resulting in inhibition of complement activation. Our results add a novel mechanism to those known to control the innate immune system.

Activation of the complement system in human nonalcoholic fatty liver disease

Activation of the innate immune system plays a major role in nonalcoholic fatty liver disease (NAFLD). The complement system is an important component of innate immunity that recognizes danger signals such as tissue injury. We aimed to determine whether activation of the complement system occurs in NAFLD, to identify initiating pathways, and to assess the relation between complement activation, NAFLD severity, apoptosis, and inflammatory parameters. Liver biopsies of 43 obese subjects with various degrees of NAFLD and of 10 healthy controls were analyzed for deposition of complement factors C1q, mannose-binding lectin (MBL), C4d, activated C3, and membrane attack complex (MAC)-associated C9. Furthermore, hepatic neutrophil infiltration, apoptosis, and pro-inflammatory cytokine expression were quantified. Whereas complement activation was undetectable in the liver of healthy subjects, 74% of the NAFLD patients showed hepatic deposition of activated C3 and C4d. C1q as well as MBL accumulation was found in most activated C3-positive patients. Strikingly, 50% of activated C3-positive patients also displayed MAC-associated C9 deposition. Deposition of complement factors was predominantly seen around hepatocytes with macrovesicular steatosis. Subjects showing accumulation of activated C3 displayed increased numbers of apoptotic cells. Importantly, hepatic neutrophil infiltration as well as interleukin (IL)-8 and IL-6 expression was significantly higher in patients showing activated C3 deposition, whereas patients with C9 deposition additionally had increased IL-1beta expression. Moreover, nonalcoholic steatohepatitis (NASH) was more prevalent in patients showing hepatic C9 or activated C3 deposition.

CONCLUSION

There is widespread activation of the complement system in NAFLD, which is associated with disease severity. This may have important implications for the pathogenesis and progression of NAFLD given the function of complement factors in clearance of apoptotic cells, hepatic fibrosis, and liver regeneration.

Polymorphisms in mannan-binding lectin (MBL)-associated serine protease 2 affect stability, binding to MBL, and enzymatic activity

Mannan-binding lectin-associated serine protease 2 (MASP-2) is an enzyme of the innate immune system. MASP-2 forms complexes with the pattern recognition molecules mannan-binding lectin (MBL), H-ficolin, L-ficolin, or M-ficolin, and is activated when one of these proteins recognizes microorganisms and subsequently cleaves complement factors C4 and C2, thus initiating the activation of the complement system. Missense polymorphisms of MASP-2 exist in different ethnic populations. To further characterize the nature of these, we have produced and characterized rMASP-2s representing the following naturally occurring polymorphisms: R99Q, D120G, P126L, H155R, 156_159dupCHNH (CHNHdup), V377A, and R439H. Only very low levels of CHNHdup were secreted from the cells, whereas quantities similar to wild-type MASP-2 were found intracellularly, indicating that this mutation results in a misfolded protein. We found that D120G and CHNHdup could not associate with MBL, whereas R99Q, P126L, H155R, V377A, R439H, and wild-type MASP-2 bound equally well to MBL. Accordingly, when D120G and CHNHdup were mixed with MBL, no activation of complement factor C4 was observed, whereas R99Q, P126L, and V377A cleaved C4 with an activity comparable to wild-type MASP-2 and H155R slightly better. In contrast, the R439H variant was deficient in this process despite its normal binding to MBL. This variant was also not able to autoactivate in the presence of MBL and mannan. We find the R439H variant is common in Sub-Saharan Africans with a gene frequency of 10%. Our results indicate that individuals with different types of MASP-2 defects may be identified through genotyping.

Effects of infectious mononucleosis and HLA-DRB1*15 in multiple sclerosis

BACKGROUND

Both human leukocyte antigen (HLA)-DRB1*15 and Epstein-Barr virus infection presenting as infectious mononucleosis (IM) are recognized as risk factors for multiple sclerosis (MS). However, their combined effect and possible interaction on MS risk is not known.

OBJECTIVE

To assess the association between HLA-DRB1*15 and risk of MS in persons with and without IM.

METHODS

We compared the prevalence of DRB1*15 in MS patients with (n = 76) and without (n = 1,836) IM with the corresponding distributions in blood donors with (n = 62) and without (n = 484) IM histories. This allowed us to estimate the relative risk of MS associated with DRB1*15 in the presence and absence, respectively, of previous IM. We then estimated the interaction between DRB1*15 and IM as the ratio of the two individual odds ratios.

RESULTS

In IM-naïve individuals, DRB1*15 carried a 2.4-fold (95% confidence interval [CI], 2.0-3.0) increased MS risk. In contrast, among persons with IM history, DRB1*15 was associated with a 7.0-fold (95% CI, 3.3-15.4) increased MS risk. Thus, the MS risk conferred by HLA-DRB1*15 was 2.9 (95% CI, 1.3-6.5)-fold stronger in the presence than in the absence of IM. Combined with previous results, this result indicates that DRB1*15-positive persons with a history of IM may be at a 10.0-fold (95% CI, 6.0-17.9) increased risk of MS compared with persons who are DRB1*15 and IM-naïve.

CONCLUSION

DRB1*15 and IM may act in synergy causing MS.

Multifactorial etiology of recurrent miscarriage and its scientific and clinical implications

A considerable proportion of recurrent miscarriage (RM) cases are caused by recurrent chromosomally abnormal conceptions. However, in younger patients and patients with multiple miscarriages, maternal causes seem to dominate. No single biomarker with a high predictive value of maternally caused RM has been identified. Non-genetic biomarkers in RM may not reflect conditions in the pregnant uterus and we rarely know whether they are causes or consequences of miscarriage. Studies of genetic biomarkers are probably the best way to reveal the pathophysiological mechanisms behind RM. Epidemiological and genetic studies suggest that RM due to maternal causes has a multifactorial background. The risk of RM in each patient is probably determined by the interaction of many genetic variants and environmental factors but only few of these have so far been identified. The genetic biomarkers for RM can probably be classified into three groups: (1) variants associated with excessive inflammatory responses and autoimmunity; (2) variants of importance for insulin and androgen sensitivity and turn-over, and (3) variants associated with thrombophilia. Identification of these markers will require whole genome association studies comprising thousands of individuals. Acknowledgement of the multifactorial background for RM has important implications for the management of patients in clinical practice.

Association between Mannose-Binding Lectin and Vascular Complications in Type 1 Diabetes

Complement activation and inflammation have been suggested in the pathogenesis of diabetic vascular lesions. We investigated serum mannose‐binding lectin (MBL) levels and polymorphisms in the MBL gene in type 1 diabetic (T1DM) patients with and without diabetic nephropathy and associated macrovascular complications. Polymorphisms in the MBL gene and serum MBL levels were determined in 199 T1DM patients with overt nephropathy and 192 T1DM patients with persistent normoalbuminuria matched for age, sex and duration of diabetes as well as in 100 healthy control subjects. The frequencies of high and low expression MBL genotypes were similar in patients with T1DM and healthy controls. High MBL genotypes were significantly more frequent in diabetic patients with nephropathy than in the normoalbuminuric group, and the risk of having nephropathy, given a high MBL genotype, assessed by odds ratio was 1.52 (1.02–2.27), P = 0.04. Median serum MBL concentrations were significantly higher in patients with nephropathy than in patients with normoalbuminuria [2306 µg/l (IQR 753–4867 µg/l) versus 1491 µg/l (IQR 577–2944), P = 0.0003], and even when comparing patients with identical genotypes, serum MBL levels were higher in the nephropathy group than in the normoalbuminuric group. Patients with a history of cardiovascular disease had significantly elevated MBL levels independently of nephropathy status [3178 µg/l (IQR 636–5231 µg/l) versus 1741 µg/l (IQR 656–3149 µg/l), P = 0.02]. The differences in MBL levels between patients with and without vascular complications were driven primarily by pronounced differences among carriers of high MBL genotypes (P < 0.0001). Our findings suggest that MBL may be involved in the pathogenesis of microvascular and macrovascular complications in type 1 diabetes and that determination of MBL status might be used to identify patients at increased risk of developing these complications.

Mannan-binding lectin MBL2 gene polymorphism in chronic hepatitis C: association with the severity of liver fibrosis and response to interferon therapy

Hepatitis C virus (HCV) is a major cause of hepatic disease and of liver transplantation worldwide. Mannan-binding lectin (MBL), encoded by the MBL2 gene, can have an important role as an opsonin and complement activating molecule in HCV persistence and liver injury. We assessed the MBL2 polymorphism in 102 Euro-Brazilian patients with moderate and severe chronic hepatitis C, paired for gender and age with 102 HCV seronegative healthy individuals. Six common single nucleotide polymorphisms in the MBL2 gene, three in the promoter (H/L, X/Y and P/Q) and three in exon 1 (A, the wild-type, and B, C or D also known as O) were evaluated using real-time polymerase chain reaction with fluorescent hybridization probes. The concentration of MBL in plasma was measured by enzyme-linked immunosorbent assay. The frequency of the YA/YO genotype was significantly higher in the HCV patients compared with the controls (P = 0.022). On the other hand, the genotypes associated with low levels of MBL (XA/XA, XA/YO and YO/YO) were decreased significantly in the patients with severe fibrosis (stage F4), when compared with the patients with moderate fibrosis (stage F2) (P = 0.04) and to the control group (P = 0.011). Furthermore, MBL2 genotypes containing X or O mutations were found to be associated with non-responsiveness to pginterferon and ribavirin treatment (P = 0.023). MBL2 polymorphisms may therefore be associated not only with the development of chronic hepatitis C, but also with its clinical evolution and response to treatment.

Indications of anti-HY immunity in recurrent placental abruption

PROBLEM

Placental abruption is a potential life-threatening condition for both the fetus and the mother, being significantly more common in pregnancies with male fetuses. The pathogenesis of placental abruption remains unknown. However, some recent reports point toward a maternal immune response against the fetus as a possible mechanism. No data exist concerning special characteristics of patients suffering recurrent placental abruptions.

METHOD OF STUDY

Identification of all patients with recurrent placental abruption in a retrospective review of 881 consecutive Caucasian women seen in our tertiary centre for recurrent pregnancy losses between 1986 and 2005. The HLA, DRB1, DRB3, 4, 5 and DQB1 genotypes of patients were compared with relevant controls.

RESULTS

Eight patients were identified with recurrent placental abruption. The patients had a total of 22 abruptions; 18 (82%) in which the fetus died. Seven patients (88%) had first-born boys, and 15 abruptions (68%) involved male fetuses. All patients with a first-born boy, except one, had HLA-class II alleles known to restrict CD4+ T-cell responses against male-specific minor histocompatibility (HY)-antigens (HLA-DRB1*15, HLA-DRB3*0301 and HLA-DQB1*05). Haplotypes with these HLA-alleles constituted 64% of the patients' haplotypes compared to 28% of those of the controls (p=0.009). Furthermore, 43% of the patients were homozygous for these haplotypes compared to 5% of controls (p=0.023).

CONCLUSION

We have found that recurrent placental abruption is exclusively almost preceded by the birth of a boy and the majority of patients have HLA-class II known to restrict CD4 T-cell reactions against HY-antigens. This indicates that maternal immunological responses against HY-antigens play a role in recurrent placental abruption.