Association of mannose binding lectin (MBL) gene
polymorphism and serum MBL concentration with
characteristics and progression of systemic lupus
R Takahashi, A Tsutsumi, K Ohtani, Y Muraki, D Goto, I Matsumoto, N Wakamiya, T Sumida
............................................................... ............................................................... .
Ann Rheum Dis 2005;64:311–314. doi: 10.1136/ard.2003.020172
Objective: To determine whether occurrence, characteristics,
and progression of systemic lupus erythematosus (SLE) are
associated with polymorphism of the mannose binding lectin
(MBL) gene and with serum MBL concentration.
Methods: Codon 54 MBL gene polymorphism of 147
patients with SLE and 160 healthy controls was determined
by polymerase chain reaction-restriction fragment length
polymorphism. Serum concentration of MBL was measured
by enzyme immunoassay. Fluctuations of serum MBL were
analysed with respect to disease characteristics and activity.
Results: Frequency of homozygosity for codon 54 minority
allele was 6% (9/147) in patients with SLE, and significantly
higher than in controls (p=0.0294, Fisher’s exact test). MBL
polymorphism in patients with SLE was not significantly
associated with disease characteristics or immunological
phenotypes. Patients homozygous for the B allele tended to
have a higher risk of infection during treatment. Levels of C3
and CH50 were slightly, but significantly, associated with
serum MBL concentration in patients with SLE homozygous
for the majority allele. During the course of SLE, serum MBL
concentration increased in 6/14 patients, and decreased in
7 after initiation of immunosuppressive treatment.
Conclusions: MBL gene polymorphism influences suscept-
ibility to SLE, but has no direct effect on disease character-
istics. Serum MBL levels fluctuate during the course of SLE in
individual patients. MBL genotyping may be useful in
assessing the risk of infection during treatment of SLE.
further combine to form a bouquet-like structure.1MBL
mediates lectin dependent activation of the complement
pathway,1and has an important role in host defence against
micro-organisms. People lacking this protein could develop
severe episodes of bacterial infections from early life.2Several
polymorphisms have been reported for the MBL gene, and a
large interindividual difference in serum MBL concentration
is caused by the possession of variant alleles. Codon 52, 54,
and 57 polymorphisms are all on exon 1 of the MBL gene,
and the presence of any of the minority alleles significantly
reduces serum MBL concentration. Furthermore, homozyg-
osity for minority alleles results in almost complete deficiency
of serum MBL.3This has been attributed to increased
degradation of the mutated protein.4
Recently, several studies have suggested that possession of
MBL minority alleles may be associated with occurrence of
annose binding lectin (MBL) is a molecule that shares
many features with C1q. MBL comprises a trimer of
three identical polypeptides, and several trimers
systemic lupus erythematosus (SLE).5 6It is known that C1q
deficiency is associated with severe symptoms of SLE.7Two
possible explanations for associations between MBL or C1q
deficiency and occurrence of SLE can be proposed: (a) MBL
and C1q can bind to and initiate uptake of apoptotic cells into
macrophages,8 9and abnormal clearance of apoptotic cells
caused by MBL or C1q deficiency may result in over-
expression of autoantigens; (b) viral infection is believed to
be one of the causes of SLE,10and MBL or C1q deficiency may
lead to more frequent infections.
This study was conducted on the premise that occurrence,
characteristics, and progression of SLE are associated with
polymorphism of the MBL gene and with serum MBL
concentration. To our knowledge, this is the first study that
has measured serum MBL concentration before and after
immunosuppressive treatment in patients with newly diag-
PATIENTS AND METHODS
Samples from 147 Japanese patients with SLE followed up at
our hospital, were used for the study. All patients fulfilled the
1997 American College of Rheumatology Classification
Criteria for SLE. Samples from 160 Japanese healthy
volunteers served as controls.
Genomic DNA was purified from peripheral blood leuco-
cytes using the DNAQuick DNA purification kit (Dainippon
Pharmaceuticals, Osaka, Japan), and stored at 230˚C. Typing
of the MBL gene allele was performed by polymerase chain
reaction-restriction fragment length polymorphism, accord-
ing to the method of Madsen et al.3The wild-type allele was
designated allele A, and codon 54 substitution (glycine to
aspartic acid) was designated allele B. Previous studies have
shown that codon 52 and 57 polymorphisms are not present
or extremely rare in the Japanese population.11Serum
concentration of MBL was measured by a specific enzyme
immunoassay using two rabbit polyclonal anti-MBL anti-
bodies as described previously.12
patients with SLE and healthy controls
Codon 54 genotypes of the MBL gene in
SLEHealthy controlsp Value
AA + AB138
(AA; 84, AB; 54)
(AA; 101, AB; 57)
Allele A, codon 54 wild type majority allele; allele B, codon 54 variant
p Value by Fisher’s exact test.
Fisher’s exact test was used to compare the frequencies of
genotypes AA/AB and BB, between disease and control
groups, and to compare clinical characteristics between
patients with genotypes AA/AB and those with BB. Mann-
Whitney’s U test was used to compare ages at diagnosis of
SLE between patients with genotypes AA/AB and those with
BB, and to compare serum MBL concentration between
patients and controls of the same genotype. Spearman’s rank
correlation test was used to compare serum MBL concentra-
tion and the levels of anti-DNA antibody, C3, C4, and CH50.
Values of p(0.05 were considered significant.
MBL gene genotypes were studied in patients with SLE and
healthy controls (table 1). Among 147 patients with SLE, 9
were homozygous for allele B, which was significantly
increased compared with controls (p=0.0294).
We analysed the difference in disease characteristics
among patients with SLE categorised by MBL genotypes.
Ages (mean (SD)) at diagnosis of SLE tended to be younger
in patients with allele B (AA: 32.5 (14.8); AB: 30.7 (15.2); BB:
23.4 (13.3)), but no significant differences were seen
(p=0.0681). Clinical characteristics, serological, and immu-
nological measures did not significantly differ between
genotype BB patients and other patients with SLE. This is
60 40 50
MBL concentration (× 102 ng/ml)
30 200 10
genotype AA patients with SLE. rs=0.253, p=0.0412 by Spearman’s
rank correlation test.
Relationship between serum MBL concentration and CH50in
CPA 500 mg div
1000 mg div
× 3 days
ADNA Ab (IU/ml)
s-MBL conc. (× 102 ng/ml)
CPA 500 mg div
1000 mg div
× 3 days
ADNA Ab (IU/ml)
s-MBL conc. (× 102 ng/ml)
CPA 500 mg div
1000 mg div
× 3 days
Onset of bacterial
Open squares, serum MBL concentrations (s-MBL ); closed squares, C reactive protein (CRP); open circles, anti-DNA antibody (ADNA Ab); closed
circles, SLE Disease Activity Index (SLEDAI); closed triangles: CH50. PSL, prednisolone; CPA, cyclophosphamide.
Fluctuation of serum MBL concentration and clinical variables during immunosuppressive treatment in patients with newly diagnosed SLE.
312Takahashi, Tsutsumi, Ohtani, et al
most probably because of the small size of the BB cohort.
However, incidence of infections requiring admission to
hospital was significantly higher in patients with genotype
BB than in other patients (genotype AA +AB; 35/132 patients,
BB; 5/8 patients, p=0.0287).
Serum MBL concentration reflected the MBL genotype of
the individual subject, in accordance with previous reports3
(data not shown). Among subjects with the same genotype,
patients with SLE tended to have a higher MBL concentration
than controls, but without statistical significance. The level of
CH50 was weakly but significantly associated with serum
MBL concentration in patients with SLE with genotype AA
(p=0.0412) (fig 1). In genotype AA patients, C3 was also
associated with serum MBL concentration, although C4 was
not (C3; p=0.0494, C4; p=0.4265). No significant relation-
ship between anti-DNA antibody titre and serum MBL was
found. In patients with other genotypes, no significant
association was seen between serum MBL concentration
and levels of anti-DNA antibody or complement components
(data not shown).
We studied fluctuation of serum MBL concentration
during immunosuppressive treatment in patients with newly
diagnosed SLE (fig 2). In patient 1 with genotype AA (fig 2A),
serum MBL increased in parallel with CH50after initiation of
Activity Index (SLEDAI) and anti-DNA antibody decreased.
In patient 2 with genotype AA (fig 2B), serum MBL
concentration decreased after initiation of methylpredniso-
lone pulse therapy, while CH50 increased. After CRP
decreased to normal levels, MBL gradually increased in
parallel with CH50. In patient 3 with genotype AA (fig 2C),
serum MBL did not show a clear trend, although disease
activity steadily decreased. In patient 4 with genotype AB
(fig 2D), serum MBL was low throughout, reflecting the MBL
genotype. When the serum MBL concentration before and
after immunosuppressive treatment was compared in 14
newly diagnosed patients, it increased in 6/14 patients
(genotype AA: 2, AB: 4), and decreased in 7 patients
(genotype AA: 5, AB: 2). There was no significant association
between increase or decrease of serum MBL concentration
and genotypes and clinical phenotypes in patients with SLE
(data not shown).
while the SLE Disease
Several studies have indicated that MBL gene polymorphism
influences susceptibility to SLE.5 6When the components of
the classical pathway of complement (C1q, C1r, C1s, C4, or
C2) are deficient, it has been suggested that abnormal
clearance of not only immune complexes13but also apoptotic
cells8contributes to the occurrence of SLE. It has been
indicated that inappropriate levels of apoptotic nuclei may be
a major source of autoantigens in SLE.14Recently, it was
reported that MBL can bind to apoptotic cells and initiate
their uptake by macrophages,9and thus, abnormal clearance
of apoptotic cells due to MBL deficiency may provide a source
of autoantigens in SLE. However, deficiency of MBL is not an
extremely high risk factor, in contrast with deficiencies of
other complement molecules such as C1q.7The precise
consequences of MBL deficiency for the onset and progres-
sion of SLE remain unclear. The lag time between occurrence
of the first symptom attributable to SLE and diagnosis of
definite SLE was reported to be significantly shorter for
variant allele carriers than in those with genotype AA.6
Therefore, the MBL gene may be a disease modifier locus
rather than a true SLE susceptibility locus. Although no
significant correlation between disease characteristics and
MBL genotypes was seen, genotype BB was significantly
associated with occurrence of infection in our patients, in
accord with a previous report.6MBL genotyping may help in
assessment of the risk of opportunistic infections in patients
The balance of MBL production and consumption deter-
mines serum MBL levels. As the presence of MBL deposits in
tissues of autoimmune patients has been demonstrated,15 16
we expected that MBL would be consumed during active
disease, and that serum MBL concentration might reflect
disease activity and pathological features of SLE in individual
patients. To test this hypothesis, we measured serum MBL
patients with newly diagnosed disease. As shown in fig 2,
serum MBL concentration did fluctuate during the course of
immunosuppressive treatment in patients with SLE, espe-
cially in genotype AA patients. In patients 1 and 2, the
increasing phase of serum MBL concentration may reflect the
decreased consumption of MBL while SLE activity gradually
decreased, and the decreasing phase may reflect reduced
production of MBL because MBL is an acute phase
inflammatory protein.17Thus, MBL levels appear to reflect
disease activity in some patients. The weak but significant
association between serum MBL concentration and serum C3
or CH50levels supports this view.
In conclusion, frequency of homozygosity for a minority
allele of the MBL gene was increased in patients with SLE
compared with controls, confirming previous studies. MBL
gene polymorphism may have no direct effect on disease
characteristics, but patients homozygous for the minority
allele had significantly more frequent episodes of infections.
Serum MBL levels did fluctuate during the course of SLE in
individual patients, although the mechanism of their
fluctuation and their consequences in SLE are unclear. The
value of serum MBL monitoring in clinical practice should be
determined in future studies.
R Takahashi, A Tsutsumi, Y Muraki, D Goto, I Matsumoto, T Sumida,
Division of Rheumatology, Department of Internal Medicine, Institute of
Clinical Medicine, University of Tsukuba, Japan
K Ohtani, N Wakamiya, Department of Microbiology, Asahikawa
Medical College, Japan
Correspondence to: Dr A Tsutsumi, 1-1-1 Tennodai Tsukuba-city,
Ibaraki 305-8575, Japan; firstname.lastname@example.org
Accepted 9 May 2004
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