close

Вход

Забыли?

вход по аккаунту

?

IgG and IgA antibodies to the collagen-like region of C1q in rheumatoid vasculitis.

код для вставкиСкачать
1646
IgG AND IgA ANTIBODIES TO THE COLLAGEN-LIKE
REGION OF Clq IN RHEUMATOID VASCULITIS
C. E. H. SIEGERT, M. R. DAHA, E. A. M. V A N
DER
VOORT, and F. C. BREEDVELD
We investigated the presence of IgG and IgA
antibodies to Clq in serum samples from 80 patients
with rheumatoid arthritis (RA), 31 patients with rheumatoid vasculitis, and 80 healthy controls. IgG and IgA
antibodies to Clq, as measured by enzyme-linked immunosorbent assay, were found in <5% of the sera
from RA patients and from healthy controls. In contrast, IgG and IgA antibodies to Clq were found in 29%
and 61%, respectively, of the sera from patients with
rheumatoid vasculitis. The occurrence of IgA antibodies
to Clq has not been previously demonstrated. These
results also demonstrate that IgG antibodies to Clq do
not occur exclusively in systemic lupus erythematosus
patients: Sera of patients with rheumatoid vasculitis
frequently contain IgG or IgA antibodies to Clq, which
contribute to immune complex formation.
Clq when Clq is bound to a solid phase ( 1 4 ) . The
recently reported associations between the presence
of circulating IgG antibodies to Clq and the occurrence of nephritis and dermatitis in SLE patients
suggest that these antibodies are of pathogenetic significance ( 5 ) .
In the present study, we investigated the occurrence of antibodies to Clq in rheumatoid vasculitis,
another disease known to be associated with circulating immune complexes (IC) (6). Since disease activity
in patients with rheumatoid vasculitis is reported to be
associated with the presence of IgA-containing IC (7),
we also investigated the presence of IgA antibodies
to Clq.
Monomeric IgG in serum samples from patients
with systemic lupus erythematosus (SLE) has been
shown to bind Clq (1). There is evidence that sera
from patients with systemic lupus erythematosus contain IgG antibodies directed against C lq, in particular,
antibodies against the collagen-like region (CLR) of
Patients. Serum samples from 31 patients with rheumatoid vasculitis and 80 patients with rheumatoid arthritis
(RA) were investigated. All patients fulfilled the American
Rheumatism Association criteria for classic or definite RA
(8). Active rheumatoid vasculitis was defined on a clinical
basis, by the presence of typical digital or nailfold infarcts,
cutaneous ulceration, or neuropathy. In 27 of these patients,
vlsculitis was also demonstrated histologically by skin or
muscle biopsy. Sixteen of the rheumatoid vasculitis patients
were women and 15 were men; their mean age was 65 years
(range 39-85). Ninety-seven percent of the rheumatoid vasculitis patients and 58% of the RA patients were positive for
rheumatoid factor (RF) by the latex agglutination serum test.
Serum samples from 80 healthy controls were also investigated. The serum samples were stored at -20°C.
Antibodies. Mouse monoclonal antibodies (MAb)
against human IgG (HB43) and IgM (HB57)(American Type
Culture Collection, Rockville, MD) were used. Mouse MAb
against human IgA (4E8) and F(ab’), fragments of rabbit
anti-human C l q and rabbit anti-human F(ab’), ( K light chain)
were isolated in our laboratories. Mouse MAb anti-CLR of
From the Departments of Rheumatology and Nephrology,
University Hospital, Leiden, The Netherlands.
Supported in part by the Dutch League Against Rheumatism.
C. E. H. Siegert, MD: Trainee, Internal Medicine, Department of Rheumatology; M. R. Daha, PhD: Professor, Internal
Medicine, Department of Nephrology; E. A. M. van der Voort:
Technician, Department of Rheumatology; F. C. Breedveld, MD:
Professor, Department of Rheumatology.
Address reprint requests to C. E. H. Siegert, MD, University Hospital, Department of Rheumatology, Building 1, C2-Q, PO
Box 9600,2300 RC Leiden, The Netherlands.
Submitted for publication November 15, 1989; accepted in
revised form May 21, 1990.
Arthritis and Rheumatism, Vol. 33, No. 11 (November 1990)
PATIENTS AND METHODS
1647
IgG AND IgA ANTIBODIES TO THE CLR OF Clq
C l q and anti-globular head (anti-GH) of C l q were kindly
provided by Dr. R. Hoekzema (Central Laboratory of the
Netherlands Red Cross Blood Transfusion Service, Amsterdam, The Netherlands) (9). All antibodies were conjugated
with biotin.
Detection of IgA and IgG binding activity to solidphase Clq. C l q was isolated from human plasma by sequential chromatography on Bio-Rex 70 (Bio-Rad, Richmond,
CA) and Bio-Gel A5 (Bio-Rad) coupled to rabbit IgG,
following a modification of a method previously described
(10). The purified C l q was shown to be hemolytically active
(1 1) and devoid of any demonstrable contaminants by 10%
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE). C l q was stored at -80°C until use.
Solid-phase C l q binding IgG and IgA were detected
by an enzyme-linked immunosorbent assay (ELISA), as
previously described (5). Briefly, 100 p1 of Clq per well (2.5
pdwell) in coating buffer (0. IM Na,CO,, 0.1M NaHCO,, pH
9.6) was incubated in 96-well microtiter plates (Titertek,
Zwanenburg, The Netherlands) for 2 hours at 37°C. After the
samples were washed 3 times with phosphate buffered saline
(PBS) plus 0.05% Tween (PBS-Tween), duplicate 1 :25 serum
dilutions in 100 pl of PBS-Tween containing 1% newborn
calf serum and 1M NaCl were added, and the samples were
incubated for 1 hour at 37°C. The samples were washed 3
times with PBS-Tween, and IgG and IgA that bound to
solid-phase Clq were detected by mouse MAb anti-human
IgG and anti-human IgA, respectively, using the biotinstreptavidin enhancement system. After 3 washes in PBSTween, o-phenylenediamine (Sigma, St. Louis, MO) and
H 2 0 2 were added, and the samples were incubated for 30
minutes. The reaction was stopped by the addition of 25 p1 of
IN H,SO,. Absorption at 492 nm was detected with a
spectrophotometer (Titertek). Titers of IgG and IgA solidphase C l q binding activity were expressed as units per
milliliter of serum, in relation to the values in 2 standard
sera, both arbitrarily set at 1,000 units/ml. The upper limit of
normal values was considered to be 2 standard deviations
above the mean level in serum samples from 80 normal
subjects; this value was 125 units/ml and 62.5 units/ml,
respectively, for the binding activity of IgG and IgA to
solid-phase Clq.
The site of the binding of IgG and IgA to solid-phase
Clq was also investigated by ELISA. Purified C l q was
separated into its GH and CLR components by pepsin
digestion. The fragments were separated by sucrose-density
gradient ultracentrifugation. The GH and CLR were detected in 500-pl fractions by mouse anti-human GH and CCR
MAb (9). Both CLR and GH were incubated in coating
buffer at a concentration of 1 d w e l l before use in the
ELISA. IgG and IgA binding activity in serum samples from
3 rheumatoid vasculitis patients and 1 healthy control, as
well as binding of rabbit F(ab'), anti-Clq to these fragments,
was tested in 1M NaCI. Binding of heat-aggregated IgG
(HAGG) was tested in 0.15M NaCl (physiologic strength).
IgG, IgA, and HAGG that bound to solid-phase Clq were
detected using mouse MAb.
Isolation of IgG and F(ab'), fragments. IgG of healthy
controls was purified from pooled human serum essentially
as described previously (12). After the samples were heat
inactivated at 56°C for 30 minutes, immunoglobulins were
precipitated with 33% (NH,),SO,. The precipitate was further purified by anion-exchange chromatography, using a
DEAE-Sephacel column (Pharmacia, Uppsala, Sweden),
and cation-exchange chromatography, using a CMC-50
Sephadex column (Pharmacia). The final IgG concentration
was 25 mg/ml. HAGG was obtained after heating the purified
IgG at 63°C for 30 minutes. HAGG binding to solid-phase
Clq and its GH and CLR fragments was tested by ELISA.
F(ab'), fragments were produced by applying 1 ml of
serum from a solid-phase C Iq binding IgG-positive rheumatoid vasculitis patient and 1 ml of serum from a healthy
control individual to a 5-ml DEAE-Sephacel column. IgG
was detected in the void volume by ELISA. F(ab'), fragments of IgG were prepared by digestion with pepsin at a
1: 10 (weight/weight) pepsin:protein ratio for 18 hours at
37°C; subsequently, the reaction was stopped by the addition
of 1M Tris base. The digestion mixtures were applied to a
5-ml protein A-Sepharose 4B column (Pharmacia) to remove
the Fc fragments and any undigested IgG. F(ab'), fragments
were detected in the void volume by rabbit anti-human K
light chain antibody. The F(ab'), fragments exhibited 1 band
of 110 kd when analyzed by SDS-PAGE. Binding of IgG
fragments to solid-phase C l q was demonstrated by a mouse
anti-human y heavy chain MAb and a rabbit anti-human K
light chain MAb.
Size determinations of Clq-binding IgA and IgG. To
determine the size of solid-phase Clq-binding IgG and IgA,
1 ml of serum from each of 3 patients with rheumatoid
vasculitis and 1 ml of serum from each of 2 healthy controls
was centrifuged at 3,000 revolutions per minute for 10
minutes, and applied to a Sephacryl-300 column (1.5 x 70
cm; Pharmacia). One patient had serum IgG binding activity
to solid-phase C l q and 2 patients had serum IgA binding
activity to solid-phase Clq, but the healthy controls had no
detectable IgG or IgA binding activity to solid-phase Clq.
Three 1.5-ml fractions were collected per hour. The total
protein content of the fractions was determined by the Folin
reaction (13). The IgM, IgA, and IgG content of every third
fraction was determined by ELISA, using mouse MAb. IgG
and IgA binding activity to solid-phase Clq in every third
fraction (diluted 1:5 and 1:3, respectively) were detected as
described.
One milliliter of the same rheumatoid vasculitis sera
was also subjected to fractionation under low pH conditions.
The column was first equilibrated with 0.01M acetate buffer
containing 0.15M NaCI, pH 4.0, and the serum was mixed
with the same volume of 0.3M glycine HCI, pH 2.8. One
milliliter of the mixture, containing 0.5 ml of the serum, was
-
Table 1. Frequency of IgG and IgA binding to solid-phase Clq in
serum samples from patients with rheumatoid arthritis, patients with
rheumatoid vasculitis, and healthy controls
No. (%) with increased serum titer
IgG binding to
IgA binding to
Group (n)
solid-phase Clq
solid-phase Clq
Rheumatoid arthritis (80)
Rheumatoid vasculitis (31)
Control (80)
9 (29)
2 (2.5)
4 (5)
1 (1)
19 (61)
2 (2.5)
1648
SIEGERT ET AL
applied to the column. The fractions were immediately
neutralized to pH 7.4 with 1M Tris HCI, pH 11.0.
Measurement of IC, complement components, and
RF. IgG and IgA containing IC were measured by polyethylene glycol precipitation (14,15). Both assays detect
large-sized IC (>25S). Titers were expressed as microgram
equivalents of aggregated immunoglobulin per milliliter of
serum (pgEq HAAG/ml). Levels of complement components C l q , C4, C3, factor B, and CHSO were determined as
previously described (16). CHSO levels were expressed as
units/ml. AU other components were measured by radial
immunodiffusion with monospecific antisera; levels were
expressed as mg%. The normal ranges were as follows: C l q
10-14 mg%, C4 17-30 mg%, C3 68-104 mg%, factor B 13-22
mg%, and CH50 25CL-580 units/ml. Levels of class-specific
RF were measured by an ELISA using monoclonal antihuman immunoglobulins and were expressed as units/ml (17).
Statistical analysis. Statistical analysis was performed
using the chi-square test and Spearman’s rank correlation. P
values less than 0.05 were considered significant.
1.5-
E
1.0-
2
?
8
05-
F.
0.0-I
0.0
-
1 .o
d
2.0
NaCl concentration fmolIl\
Figure 2. Effect of NaCl concentration on solid-phase Clq (spclq)
binding of IgG and IgA in diluted serum (1:25) from a patient with
rheumatoid vasculitis. Rabbit F(ab‘), anti-CIq was used as a control
for F(ab’),-mediated binding, and heat-aggregated IgG (AIgG) was
used as a control for Fc-mediated binding. OD = optical density.
RESULTS
++
+
+
0
.”
I +
*
I
+ I
- 4o I
+ I
1
I
ro0J-l’
HEALTHY
CONTROL
RHEUMATOlD
ARTHRITIS
RHEUMATOID
VASCULlTlS
Figure 1. Titers of IgG (top) and IgA (bottom) binding activity to
solid-phase Clq, measured in the sera of 80 healthy controls, 80
rheumatoid arthritis patients, and 31 rheumatoid vasculitis patients.
The dotted line indicates the upper limit of normal values, defined as
2 SD above the mean in the sera of 80 healthy controls. The upper
limit was 125 unitdm1 for IgG and 62.5 unitslml for IgA.
Frequency of IgG and IgA binding activity to
solid-phase Clq. IgG binding activity to solid-phase
Clq could be detected in serum samples from 4 RA
patients (5%) and 2 healthy controls (2.5%). IgA
binding activity to solid-phase C lq could be detected
in the serum of only 1 RA patient (l%), and in serum
samples from 2 healthy controls (2.5%). In contrast, 9
serum samples (29%) from the rheumatoid vasculitis
patients studied contained IgG binding activity to
solid-phase Clq, and 19 (61%) contained IgA binding
activity to solid-phase Clq (Table 1). In 50% of the
patients with IgG binding activity to solid-phase Clq,
IgA binding activity to solid-phase Clq was also present
in the serum, and in 16% of the patients with IgA
binding activity to solid-phase Clq, serum IgG binding
activity to solid-phase Clq could be detected. The
titers of IgG and IgA binding activity to solid-phase
Clq are depicted in Figure 1.
Effect of ionic strength on binding of IgG and IgA
to solid-phase Clq. To analyze the affinity of the binding
to solid-phase Clq, the binding activity of 1:25 dilutions of serum samples from 2 rheumatoid vasculitis
patients, 1 with high IgG and 1 with high IgA binding
activity to solid-phase Clq, was tested under increasing NaCl concentrations. In control experiments, the
binding of rabbit F(ab’), anti-Clq and HAGG to Clq
was also studied. IgG and IgA binding to solid-phase
Clq in serum from rheumatoid vasculitis patients did
not change when the NaCl concentration was increased to 2M (Figure 2). Similar binding characteris-
1649
IgG AND IgA ANTIBODIES TO THE CLR OF Clq
0 HEALTHY CONTROL
W RVPATIENT
1.o
I
N
m
0
8
0.5
0.0
IgG
SERUM
F(ad)2
Fc
Figure 3. Solid-phase Clq binding activity of IgG in serum, and of
purified IgG, F(ab‘),, and Fc, from a patient with rheumatoid
vasculitis (RV) and a healthy control. The activity levels for IgG and
its fragments are adjusted for molar concentrations. OD = optical
density.
tics were seen with rabbit F(ab’), anti-Clq. However,
the binding of HAGG to Clq disappeared when the
NaCl concentration was increased above 0.1SM.
These results indicate that the Clq binding of both IgG
and IgA in serum from rheumatoid vasculitis patients
1/25
1/50
1/100
11200
is of high affinity, and therefore might be F(ab’),
mediated, rather than Fc mediated.
F(ab‘),-mediated binding of IgG to solid-phase
Clq. To further delineate the nature of the binding of
IgG to solid-phase Clq, serum IgG from rheumatoid
vasculitis patients and from healthy controls was purified. Binding to solid-phase Clq by representative
samples from patient and healthy control serum IgG,
purified IgG, and F(ab’), fragments prepared from this
IgG is shown in Figure 3. Optical densities are presented for equivalent molar concentrations of IgG and
its F(ab’), and Fc fragments to allow comparison of
the ELISA results. To compare F(ab’), and Fc fragments with whole IgG, ratios of 0.67 and 0.33, respectively, were used. The binding activity to solid-phase
Clq appeared to be higher in the purified serum IgG
compared with unfractionated serum. The F(ab’)2
fragments appeared to be responsible for the IgG
binding to solid-phase Clq. Little binding to solidphase Clq by IgG or its derivatives was observed in
the serum of the healthy control.
11400
1/25
serum dilutions
1/50
1/100
1/200
1/400
serum dilutions
C
D
10-
05-
0.0.
0
I
.
r
:.
v
1650
Localization of the binding of IgA and IgG to
solid-phase Clq. CLR and G H fragments of Clq were
prepared in order to study the binding site of solidphase Clq to IgG and IgA in serum from rheumatoid
vasculitis patients. Dilutions of serum samples from 2
rheumatoid vasculitis patients were incubated with
solid-phase Clq and the CLR and GH of C l q under
high ionic strength conditions. In control experiments,
we also studied the binding of rabbit F(ab'), anti-C lq
under high ionic strength conditions, and HAGG binding under physiologic ionic strength conditions. IgG
(Figure 4A) and IgA (Figure 4B) in the sera of both
rheumatoid vasculitis patients bound to solid-phase
Clq and to the CLR of Clq in a dose-dependent
manner; no binding to the GH of Clq was observed.
F(ab'), fragments of polyclonal rabbit anti-C lq bound
to solid-phase Clq and to its fragments; binding to the
CLR of C l q was more pronounced than was binding to
the GH of Clq (Figure 4C). HAGG bound to both
solid-phase Clq and the GH of Clq. Binding of HAGG
to the CLR of Clq was not observed (Figure 4D).
Dilutions of serum from a healthy control did not bind
to solid-phase C l q or to the Clq fragments (data not
shown). The results indicate that IgG and IgA in serum
of rheumatoid vasculitis patients bind to the CLR of
solid-phase C 1 q.
Molecular weight determination of solid-phase
Clq binding IgG and IgA. To determine the size of
both solid-phase Clq binding IgG and solid-phase C lq
binding IgA, we fractionated serum samples from 3
rheumatoid vasculitis patients, 1 containing high titers
of IgG binding activity to solid-phase Clq and 2
containing high titers of IgA binding activity to solidphase Clq, as well as 2 serum samples from healthy
controls. The binding activity of IgG and IgA to
solid-phase C lq was then measured in these fractions.
When fractionated under physiologic pH conditions,
both the IgG and the IgA binding to solid-phase C l q in
sera from the rheumatoid vasculitis patients were
predominantly found in the fractions containing high
molecular weight material (Figures 5A and 6A). When
the same serum samples were fractionated under low
pH conditions to induce dissociation of the IC, the IgG
binding activity to solid-phase Clq was found only in
the fractions containing monomeric IgG (Figure 5B).
The IgA binding activity to solid-phase Clq was found
in the fractions with molecular weights corresponding
to those of both dimeric IgA and monomeric IgA
(Figure 6B).
In Figures 5B and 6B, the optical densities for
the IgG and IgA binding activity to solid-phase C l q
SIEGERT ET AL
1.5
A
1
30
40
so
80
70
"1
80
B
1 .o
C
1.5-
1.0-
05-
00
30
40
50
60
70
80
fradion number
Figure 5. Solid-phase Clq binding activity of serum IgG fractionated by Sephacryl-300 column chromatography. One-milliliter serum samples from a patient with rheumatoid vasculitis and a healthy
control were fractionated. A, Patient serum fractionated at pH 7.4.
B, Patient serum fractionated at pH 4.0. Optical densities (OD) for
IgC binding activity were doubled to adjust for the sample volume
applied to the column. C, Control serum fractionated at pH 7.4.
d-lgA = dimeric IgA; m-IgA = monomeric IgA.
were doubled to adjust for the volume applied to the
column. Although this is not the most appropriate way
to present the data, the results are only meant to give
an indication of the molecular weight of immunoglobulins binding to solid-phase Clq. No binding activity
IgG AND IgA ANTIBODIES TO THE CLR OF Clq
1651
1.51
30
1.5-
1.0-
0.5
-
40
50
60
70
80
C
suggest that the binding activity of IgA to solid-phase
Clq has an important role in the formation of IC in
patients with rheumatoid vasculitis.
Comparison of serum levels of solid-phase Clq
binding immunoglobulins, complement components,
and RF. To investigate a possible association between
levels of both IgG and IgA binding to solid-phase Clq
SIEGERT ET AL
1652
Since rheumatoid vasculitis patients are known
to have high titers of serum RF (18), we performed an
additional experiment to exclude the effect of RF on
the measurement of solid-phase C 1q binding immunoglobulin activity. Dilutions of serum samples with high
titers of IgG-RF or IgA-RF but without detectable
binding of either IgG or IgA to solid-phase Clq were
added to 1:25 dilutions of serum samples with high
levels of IgG or IgA binding to solid-phase Clq but
without detectable IgG-RF or IgA-RF. Neither
IgG-RF positivity nor IgA-RF positivity influenced the
results of the ELISA used to measure binding activities of IgG and IgA to solid-phase Clq (data not
shown).
DISCUSSION
In the present study, we determined the prevalence and specificity of antibodies to solid-phase Clq
in serum from patients with rheumatoid vasculitis and
RA. A higher prevalence of both IgG and IgA antibodies to Clq was found in serum from patients with
rheumatoid vasculitis, compared with their prevalence
in serum from healthy controls and RA patients.
Evidence that the IgA and IgG binding to solid-phase
Clq in serum from patients with rheumatoid vasculitis
does in fact reflect the presence of autoantibodies
against solid-phase C lq was obtained by several observations. Similar to the case of rabbit antibody to
Clq, IgG and IgA in serum samples from rheumatoid
vasculitis patients continued to bind to solid-phase
Clq when the ionic strength of the serum dilutions was
increased from 0.15M to 2.OM NaCI. In contrast, the
binding of HAGG to solid-phase Clq was markedly
affected by this procedure. Such an affinity of the
binding of IgG and IgA to solid-phase Clq is indicative
of the presence of antibody to Clq.
Further evidence for the presence of Clq antibody in the serum of patients with rheumatoid vasculitis was obtained by experiments with pepsin-digested
IgG isolated from rheumatoid vasculitis serum. The
solid-phase Clq binding of IgG from these patients
appeared to be mediated by the F(ab’), fragment.
Since this digestion procedure leaves only F(ab’),
fragments of IgG intact (19), the effect of increased
levels of IgA binding activity to solid-phase Clq was
not taken into account.
IgA and IgG antibodies to Clq in the seriim of
rheumatoid vasculitis patients showed apparent highaffinity binding to the CLR of Clq. Immunoglobulin
binding to the CLR fragment was even higher than
binding to intact Clq, suggesting that pepsin digestion
exposes epitopes on the CLR of Clq. Fractionation
experiments demonstrated that IgG and IgA antibody
to Clq could be found in circulating IC. These complexes were dissociated under acidic conditions, after
which the antibody to Clq was found in the fractions
that corresponded with monomeric IgG, and with both
dimeric and monomeric IgA. The clear correlation
found between titers of IgA antibody to Clq and
IgA-containing IC also suggests that C lq antibodies
contribute to IC formation in rheumatoid vasculitis.
The binding activity of these IC to solid-phase Clq
suggests that IgG and IgA antibodies to Clq in the
complexes are still able to bind to solid-phase Clq by
means of unoccupied binding sites.
Several groups have reported that sera of -50%
of SLE patients contain IgG antibodies to Clq
(1,5,20). The observation that monomeric IgG in the
serum of SLE patients could bind to Clq was made
long before the actual antibody nature of this binding
was elucidated (21). It was concluded that the binding
activity of IgG to solid-phase Clq in sera from SLE
patients is due to the presence of antibodies to the
CLR of Clq and not to IC, since high salt concentrations did not eliminate the binding of SLE serum IgG
to solid-phase Clq, whereas the binding of IC was
markedly affected by this procedure (1-3). Furthermore, F(ab’), fragments of IgG from these patients
bound to solid-phase Clq, and intact IgG bound to the
CLR of Clq that had been prepared by pepsin digestion of native Clq ( 1 4 ) . Similar experiments were
performed in the present study to demonstrate the
presence of IgG antibodies to Clq in the serum of
rheumatoid vasculitis patients. IgG antibodies to Clq
have also been observed in patients with hypocomplementemic urticaria1 vasculitis syndrome (22), and in
patients with membranoproliferative non-lupus glomerulonephritis (23). Thus, IgG antibodies to Clq may not
be specific for a particular disease. Further studies
should be performed to delineate the clinical significance of the detection of antibodies to Clq.
Binding of components of both complement
system pathways to immunoglobulins of several
classes is well established. The classical pathway is
activated by IC containing IgM or IgG that bind with
low affinity to Clq through its globular heads (24).
More recently, the alternative pathway of the complement system has been demonstrated to be activated by
IgA-containing IC (25,26). The demonstration of IgG
antibodies to Clq in the serum of SLE patients demonstrated that not only IC, but also low molecular
1653
IgG AND IgA ANTIBODIES TO THE CLR OF Clq
weight immunoglobulins, are able to bind to Clq.
Binding of IgA to Clq has been reported, but the
results of different studies have conflicted (27-29). The
reported interaction was of low affinity and presumably not dependent on an antigen-antibody interaction. The high-affinity binding of IgA to Clq that we
found in the serum of rheumatoid vasculitis patients
has not been previously reported.
A possible pathogenetic role of antibodies to
Clq was suggested by the association between the
presence of these antibodies in patients with SLE and
the occurrence of nephritis (13).A strong association
between titers of IgG antibody to Clq and decreased
levels of complement components of the classical
pathway was also demonstrated in patients with SLE
(5). These findings suggested that either antibodies to
Clq or IC that contain antibodies to Clq can activate
the complement system. However, the normal levels
of complement components of both the classical and
the alternative pathway found in all rheumatoid vasculitis patients studied do not support this suggestion.
Much attention has been paid to the pathogenetic role of IC in the development of this type of
vasculitis in RA. Experimental studies showed that
similar lesions could be reproduced by the intravenous
administration of IC (30). Clinical studies showed that
patients with rheumatoid vasculitis have higher titers
of circulating IC than do patients with uncomplicated
RA, and the largest differences were found for IC
containing IgA (6,7).
The present study shows that IgG and IgA
antibodies to Clq occur in rheumatoid vasculitis and
participate in the formation of IC. This may influence
the disease process by several mechanisms. These
include changes in the size and composition of IC, and
interference with the activation of the classical pathway of the complement system. This, in turn, may lead
to changes in the clearance, degradation, tissue deposition, and inflammatory activity of the IC. Binding of
IgG antibodies to solid-phase C lq was scarcely inhibited by fluid-phase Clq, in contrast to Clq bound to an
IC (3). Therefore, it has been suggested that antibodies
to Clq are directed against neoantigens on the CLR,
which are exposed by Clq only in a solid-phase
situation (4). Binding to an IC is one of the possible
solid-phase situations in which Clq can occur. As a
result of such binding, C lq undergoes conformational
changes (31). The demonstration of antibodies to Clq
in another disease known for the presence of circulating IC suggests that the presence of IC stimulates the
production of these antibodies. The high prevalence of
antibodies to C Iq in rheumatoid vasculitis patients
compared with RA patients may be further explained
by the higher Clq content of IC in rheumatoid vasculitis, compared with RA (32).
This study demonstrates that IgA antibodies
to Clq contribute to the formation of IgA-containing
IC in rheumatoid vasculitis. The predominance of
IgA antibodies to Clq in a disease known for the frequent occurrence of circulating and deposited IgAcontaining IC suggests that these antibodies are of
pathogenetic significance. Further studies are warranted to explore the occurrence and possible pathogenetic role(s) of IgA antibodies to Clq in the
vasculitis-related diseases.
ACKNOWLEDGMENT
We thank Professor B. H. Bernstein for assistance in
the revision of the manuscript.
REFERENCES
1. Uwatoko S, Aotsuka S, Okawa M, Egusa Y, Yokohari
R, Aizawa C, Suzuki K: Characterization of Clqbinding IgG complexes in systemic lupus erythematosus. Clin Immunol Immunopathol 30: 104126, 1984
2. Uwatoko S, Aotsuka S, Okawa M, Egfusa Y, Yokohari
T, Aizawa C, Suzuki K: The C l q solid-phase radioimmunoassay: evidence for detection of antibody directed against the collagen-like region of C l q in sera
from patients with systemic lupus erythematosus. Clin
Exp Immunol69:98-106, 1987
3. Uwatoko S, Mannik M: Low molecular weight Clqbinding immunoglobulin G in patients with systemic
lupus erythematosus consist of autoantibodies to the
collagen-like region of Clq. J Clin Invest 82:816-824,
1988
4. Antes U, Heinz H-P, Loos M: Evidence for the presence of autoantibodies to the collagen-like portion of
Clq in systemic lupus erythematosus. Arthritis Rheum
31:457464, 1988
5. Siegert CEH, Daha MR, Westedt M-L, van der Voort
EAM, Breedveld FC: Nephritis and dermatitis in systemic lupus erythematosus are strongly associated with
the occurrence of IgG autoantibodies against the first
subcomponent of complement. Arthritis Rheum 32
(suppl 4):S74, 1989
6. Jans H, Halberg P, Lorenzen I: Circulating immune
complexes in rheumatoid arthritis with extra-articular
manifestations. Scand J Rheumatol 12:215-218, 1983
7. Westedt M-L, Daha MR, de Vries E, Valentijn RM,
Cats A: IgA containing immune complexes in rheumatoid vasculitis and in active rheumatoid disease. J Rheumatol 12:449455, 1985
SIEGERT ET AL
8. Ropes MW, Bennett GA, Cobb S, Jacox R, Jessar RA:
1958 revision of diagnostic criteria for rheumatoid arthritis. Bull Rheum Dis 9:175-176, 1958
9. Daha MR, Klar N , Hoekzema R, van Es LA: Enhanced
production by human peripheral lymphocytes induced
by aggregated Clq. J Immunol 144:1227-1232, 1990
10. Tenner AJ, Lesavre PH, Cooper NF: Purification and
radiolabeling of human Clq. J Immunol 127:648-653,
1981
11. Kolb WP, Kolb LM, Podack ER: Clq: isolation from
human serum in high yield by affinity column chromatography and development of a highly sensitive hemolytic assay. J Immunol 122:2103-2110, 1979
12. Breedveld FC, Lafeber GJM, de Vries E, van Krieken
JHJM, Cats A: Immune complexes and the pathogenesis
of neutropenia in Felty's syndrome. Ann Rheum Dis
45:69&702, 1986
13. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ:
Protein measurement with the Folin phenol reagent. J
Biol Chem 193:265-275, 1951
14. Valentijn RM, van Es LA, Westedt M-L, Daha MR: The
detection of circulating immune complexes containing
immunoglobulin G. J Clin Lab Immunol 14:73-79, 1984
15. Valentijn RM, van Es LA, Daha MR: The specific
detection of IgG, IgA and the complement components
C3 and C4 in circulating immune complexes. J Clin Lab
Immunol 14:81-86, 1984
16. Daha MR, Berdina RM, Thomson J, Kauffmann RH,
Nicholson-Wellen A, Veltkamp JJ, Briet E: Combined
hereditary deficiency of the sixth component of complement and factor VIII coagulant activity in a Dutch
family. Clin Exp Immunol48:733-738, 1982
17. Otten HG, Daha MR, de Rooy HH, Breedveld FC:
Quantitative detection of class-specific rheumatoid factors using mouse monoclonal antibodies and the biotin/
streptavidin enhancement system. Br J Rheumatol 28:
310-316, 1989
18. Westedt M-L, Herbrink P, Molenaar JL, de Vries E,
Verlaan P, Stijnen Th, Cats A, Lindeman J: Rheumatoid
factors in rheumatoid arthritis and vasculitis. Rheumatol
Int 5:209-214, 1985
19. Killander J: Gamma globulins: 1%7 studies on the
structure of human IgM globulins, Nobel Symposium 3.
Stockholm, Almqvist and Wiksell, 1967
20. Wener MH, Uwatoko S, Mannik M: Antibodies to the
collagen-like region of C l q in sera of patients with
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
autoimmune rheumatic disease. Arthritis Rheum 32:
544-551, 1989
Agnello V, Koffler D, Eisenberg JW, Winchester RJ,
Kunkel HG: Clq precipitins in the sera of patients with
SLE and other hypocomplementic states: characterization of high and low molecular weight types. J Exp Med
134 (suppl):228S240S, 1971
Wisnieski JJ, NaE GB: Serum IgG antibodies to Clq in
hypocomplementemic urticarial vasculitis syndrome.
Arthritis Rheum 32: 1 1 19-1 127, 1989
Strife CF, Leahy AE, West CD: Antibody to a cryptic,
solid phase C lq antigen in membranoproliferative nephritis. Kidney Int 3k836-842, 1989
Augener W, Grey HM, Cooper NR, Muller-Eberhard
HJ: The reaction of monomeric and aggregated immunoglobulins with C1. Immunochemistry 8: 101 1-1020,
1971
Hiemstra PS, Gorter A, Stuurman ME, van Es LA,
Daha MR: Activation of the alternative pathway of
complement by human serum IgA. Eur J Immunol
17:321-326, 1987
Rits M, Hiemstra PS, van Es LA, Bazin H , Vaerman
J-P, Daha MR: Complement-mediated solubilization of
rat IgA immune precipitates. Mol Immunol 24:10471053, 1987
Romer W, Rother U, Roelcke D: Failure of IgA cold
agglutinin to activate C. Immunobiology 117:4146, 1980
Burritt MF, Calvanico NJ, Mehta S, Tomasi TB Jr:
Activation of the classical complement pathway by Fc
fragment of human IgA. J Immunol 1183723-725, 1987
Hiemstra PS: Activation of the alternative pathway of
the complement system by immunoglobulin A (thesis).
Leiden University, Leiden, The Netherlands, 1988
McCluskey RT, Benacerraf B, Poter JL, Miller F: The
pathologic effects of intravenously administered soluble
antigen-antibody complexes. J Exp Med 1 1 1: 181-194,
1960
Golan MD, Burger R, Loos M: Conformational changes
in Clq after binding to immune complexes: detection of
neoantigens with monoclonal antibodies. J Immunol
129:445447, 1982
Westedt M-L, Daha MR, Baldwin WM 111, Stijnen T,
Cats A: Serum immune complexes containing IgA appear to predict erosive arthritis in a longitudinal study in
rheumatoid arthritis. Ann Rheum Dis 45:809-815, 1986
Документ
Категория
Без категории
Просмотров
0
Размер файла
780 Кб
Теги
like, iga, antibodies, igg, vasculitis, regions, collagen, rheumatoid, c1q
1/--страниц
Пожаловаться на содержимое документа