close

Вход

Забыли?

вход по аккаунту

?

Estimation of the relative avidity of 19S IgM rheumatoid factor secreted by rheumatoid synovial cells for human IgG subclasses.

код для вставкиСкачать
722
ESTIMATION OF THE RELATIVE AVIDITY OF 19s IgM
RHEUMATOID FACTOR SECRETED BY RHEUMATOID
SYNOVIAL CELLS FOR HUMAN IgG SUBCLASSES
DICK L. ROBBINS, JEFFREY SKILLING, WILLIAM F. BENISEK, and RICHARD WISTAR, JR.
19s IgM rheumatoid factors (RF) may play an
important role in sustaining inflammation in rheumatoid arthritis (RA). As yet, no unique antigenic specificity for RF in RA has been identified. Because the
synovium is central to the pathogenic changes in RA, RF
produced therein might be pathogenically more important than serum RF. Therefore, we examined the reactivity and relative avidity of 19s IgM-RF in serum and
rheumatoid synovial cells (RSC) from 20 patients with
seropositive RA. Reactivities were determined by competitive inhibition of serum RF hemolytic activity and
RSC RF-plaque-forming cells (PFC) by added soluble
antigen, i.e., monomeric human IgG subclasses. Estimation of relative avidities of RSC RF for human IgG
subclasses was done by calculation of fractional RF
expression in the RSC RF-PFC assay following inhibition by IgG subclasses. RSC RF had greatest reactivity
with IgG3 and IgG1, some reactivity with IgG2, and the
least reactivity with IgG4. Serum RF reacted most with
IgGl and IgG2, reacted some with IgG4, but reacted
poorly with IgG3. The antigenic determinants with
From the Department of Medicine and the Department
of Biological Chemistry, University of California School of Medicine, Davis, and the Naval Medical Research Institute, Bethesda,
Maryland.
Supported by NIH grant AM-32287.
Dick L. Robbins, MD: Associate Professor of Medicine,
University of California School of Medicine, Davis; Jeffrey Skilling:
Medical Student, University of California School of Medicine,
Davis; William F. Benisek, PhD: Professor of Biological Chemistry,
University of California School of Medicine, Davis; Richard Wistar,
Jr., MD, PhD: Director, Infectious Diseases Program Center, Naval
Medical Research Institute, Bethesda, Maryland.
Address reprint requests to Dick L. Robbins, MD, TB 192,
Rheumatology/Allergy/Clinical Immunology, University of California School of Medicine, Davis, CA 95616.
Submitted for publication June 28, 1985; accepted in revised form November 4, 1985.
Arthritis and Rheumatism, Vol. 29, No. 6 (June 1986)
which RSC RF reacted were common to many IgG3
molecules. The highest relative avidity of RSC RF was
for IgG3. These observations indicate a selective deficiency of serum RF compared with RSC RF and suggest
an important pathogenic role for these qualitatively
different RSC RF molecules for in situ RF immune
complex-mediated inflammation in RA synovial tissue.
19s IgM rheumatoid factors (RF) in rheumatoid
arthritis (RA) are polyclonal autoantibodies directed at
antigenic determinants on the Fc portion of IgG (1).
Clinical and experimental evidence suggests an important role for RF-IgG complexes in sustaining inflammation in RA. However, serum RF demonstrate a
heterogeneity of reactivities with determinants on IgG
Fc, including species differences in R F reactivities. In
fact, many serum RF have greater reactivity with
rabbit IgG than with human IgG (2), and the avidity of
serum RF for human IgG is low, with an association
constant of 104-105 literdmole (3,4). Serum RF from
RA patients bind with human IgG subclasses 1, 2, and
4,but bind poorly with IgG3 (5,6). These observations
have confused our understanding of the pathogenic
role of RF in RA.
However, the weakness of determinations at
the serum level is that they reflect only accumulated
antibody produced during the time preceding the
bleeding, whereas the plaque-forming cell (PFC)
method allows determination of the reactivity and
avidity characteristics of antibodies produced at a
given time by a given cell (7,8). In this regard, RF-PFC
from RA peripheral blood mononuclear cells (PBMC)
have greater reactivity with human IgG than with
19s IgM RF AVIDITY
rabbit IgG, in contrast with autologous serum RF (9).
Moreover, the presence of PBMC RF-PFC in RA
patients correlates with aggressive synovitis and active vasculitis (2). Since the synovium is central to the
pathologic process in RA, RF produced by rheumatoid
synovial cells (RSC) may have greater pathogenic
imLportance than serum RF.
Inhibition of hemolytic plaque formation by
competing soluble antigen has been used as a measure
of relative antibody affinity (univalent interaction) or
avidity (multivalent interaction) at the cellular level.
For example, the concentration of antigen required to
inlhibit a given amount of antibody is inversely proportional to the mean affinity-avidity of the antibody.
Thus, the concentration of antigen required to completely inhibit 50% of PFCs (PI50) has been used as a
mleasure of relative antibody avidity. However, relative antibody avidity is more accurately measured in
PFC assays by calculation of fractional antibody expression following inhibition by specific antigen. This
is done by measuring individual plaque diameters and
and expressthen calculating plaque volume (116 d3)
in,p it as percent of control (Ab50). To simplify analysis, a quantity proportional to total plaque volume, the
sum of the cubes of individual plaque diameters (Zd3),
can be used. High avidity antibody produces larger
diameter plaques than does low avidity antibody. This
provides a more accurate estimate of relative antibody
avidity than PI50 (1G12).
This study further characterizes RSC R F
reactivities with human IgG subclasses and estimates
the relative avidities of RSC R F for human IgG subclasses.
MATERIALS AND METHODS
Source of tissue. Synovial tissue was obtained during
clinically indicated surgical procedures (synovectomy, total
joint replacement) on patients with definite or classic
seropositive RA according to the American Rheumatism
Association revised criteria (13). The method used has been
previously described (1435). Briefly, tissue obtained during
surgery was collected under conditions of local, temporary
ischemia, so that contamination of the tissue with peripheral
blood was minimal. In all cases, synovial cells were washed
during processing to remove serum RF. Specimens were
collected in Cat
and Mg++-free Hanks' balanced salt
solution (Gibco, Grand Island, NY) containing 2.5 IU/ml of
heparin and antibiotics (50 IU/ml penicillin and 50 mg/ml
streptomycin) and were processed immediately. The tissue
was minced and dissociated by treatment with 0.5 mg/ml
crude collagenase and 0.15 mg/ml DNase (collagenase type 1
and DNase type 1; Sigma, St. Louis, MO) at 37°C for 60
minutes, followed by filtration through nylon mesh (single
layer, pore size 200 pm).
+ -
723
The eluted cell suspension was centrifuged (150g for
15 minutes at 4"C), and the cells were resuspended in tissue
culture medium RPMI 1640 supplemented with 10% (heatinactivated; 56°C for 30 minutes) fetal calf serum (FCS;
RPMI 1640-10% FCS; Gibco). The cells were washed 3
times by suspension in RPMI 1640-10% FCS, centrifuged at
1,200 revolutions per minute for 10 minutes at 4"C, and then
resuspended in RPMI 1640-10% FCS in antibiotics. Cells
were counted in a hemocytometer and viability was assessed
by trypan blue dye exclusion. Cell viability consistently was
>90%. Cell suspensions were then adjusted to contain 1-10
x lo6 viable cells/ml and were used in the plaque assay
system. Cell yields varied, depending on the amount and the
quality of the tissue obtained.
Preparation of the sensitizing antibody. The IgG fraction of rabbit anti-sheep red blood cell (SRBC) hemolysin
was reduced and alkylated to destroy its ability to fix
complement. The hemolysin was further treated with 0.15M
glycine HC1, pH 2.5, as previously described ( 2 ) , to enhance
the sensitivity of the RF-PFC assay.
Source of complement. Lyophilized guinea pig serum
(Hyland Laboratories, Los Angeles, CA) was reconstituted
with the diluent provided by the distributor and used as the
complement source.
Synovial PFC assay for RF production. The liquid
monolayer plaque assay system was used because it is more
sensitive than the agarose gel technique for the detection and
measurement of PFC.
Slide chambers were assembled using 3 pieces of
double-sided adhesive tape (Scotch Brand Tapes; 3M Company, St. Paul, MN) to divide the slides into approximately
equal areas. Forty microliters of RPMI 1640 supplemented
with 5% FCS (heat-inactivated; 56°C for 30 minutes) was
pipetted into small glass tubes (12 x 75 mm). To this was
added 20 pl of the sensitized SRBC. Forty microliters of
inhibitor (monomeric IgG) was then added, followed by 20 p1
of complement (1:2.5 dilution), and 100 pl of RSC. The tube
contents were thoroughly mixed and used to fill the slide
chambers, which were sealed with paraffin wax and incubated in a horizontal position at 37°C for 90 minutes. The
plaques were counted macroscopically. Results were expressed as the number of RF-PFC per lo6 viable cells
examined. Unsensitized SRBC were treated in exactly the
same manner as that described for IgG-sensitized SRBC.
Control slides included the use of unsensitized SRBC in
place of sensitized SRBC, and SRBC used without synovial
cells, to assess spontaneous lysis under assay conditions. All
determinations were run in duplicate.
Plaque diameters were measured by placing the slide
chambers on a Leitz microslide projector (2.5 x objective).
The image was projected on a screen to a 40x magnification
(chosen because it produced adequate size and resolution to
allow accurate measurement of RSC RF-PFC diameter) and
plaque diameters were then measured. The RSC RF-PFC
diameters were then cubed, summed, and averaged for each
slide (Zd3). It should be noted that 2d3 is proportional to
unbound RF.
Preparation of monomeric IgG. Human and rabbit
Cohn fraction I1 preparations were further purified by ion
exchange chromatography on DEAE cellulose as described
(15).
ROBBINS ET AL
724
Myeloma proteins were isolated using ion exchange
chromatography, followed by gel permeation chromatography where indicated. An enzyme-linked immunosorbent
inhibition assay was used to assess the amount of contamination of purified human myeloma proteins with other subclasses as previously described (15). All of the subclass
proteins used in the RSC RF-PFC assays were 98-99% pure
when determined by this method. When examined by density gradient ultracentrifugation using 1040% sucrose, all
IgG preparations remained in monomer form throughout the
RSC RF-PFC assay conditions. All IgG preparations were
negative for RF activity when examined using radioimmunoassay (16).
Hemolytic assay of serum RF. The hemolytic activity
of 19s IgM serum RF was assayed as previously described
(9,15). To tubes containing 0.1 ml of serial dilutions of RA
serum in buffer was added 0.1 ml of 1% sensitized SRBC
prepared with treated rabbit hemolysin. After incubation at
37°C for 60 minutes and at 4°C for 90 minutes, 1.O ml of cold
veronal buffered saline (GVB++)
was added to all the tubes,
which were then centrifuged at 2,000 rpm for 5 minutes at
4°C. The supernatants were discarded. To the cells was
added 0.4 ml of 1:40 complement previously absorbed in the
cold (4°C) with SRBC. The tubes were incubated at 37°C for
-T
1
Table 1. Myeloma IgG subclass proteins examined in a rheumatoid factor plaque-forming cell assay
Subclass
Light chain
IgG 1
He
Le
Wi
Wilk
IgG2
Gu
KO
Ti1
IgG3
Be
Cr
Fr
Hus
La
Me
IgG4
>
A
K
A
A
A
K
K
K
K
K
K
K
K
c1
A
Te
K
I10
100
TT
r
:z
4-
90
c
0
4
80
0"
~2 70
-
>4-
05
60
kg
40
30
5 " 50
zz
2
$
20
10
C
250
500
Figure 1. Comparison of monomeric polyclonal human IgG and monoclonal human IgG subclasses 1 4 as inhibitors of hemolytic rheumatoid
factor (RF) activity in rheumatoid synovial cells (RSC) (A) and in autologous serum (B). Plaque-forming cell (PFC) assays were prepared with
synovial cells from a single source of tissue and variable concentrations of IgG. IgG was added as a solution in phosphate buffered saline. The
control slides were similar to the experimental slides except that IgG was not added. All assays were done in duplicate. Results from 4 other
RSC donors were similar. Error bars indicate 1 SD. Hu = polyclonal human IgG.
19s IgM RF AVIDITY
725
=2 100
g
90
0
0
80
z
70
c
1
c.
60
50
2
40
2
30
4.
a"
2
p:
T
T
-
T
r
20
10
0
1000
25
IgG ( p w m l )
Figure 2. Comparison of 5 IgG3 proteins with IgGl and IgG4 as
inhibitors of synovial cell number. Plaque assay conditions were as
described in Materials and Methods. Results from 3 other RSC
donors were similar. Error bars indicate 1 SD. RSC RF-PFC =
rheumatoid synovial cell rheumatoid factor plaque-forming cell; Hu
= polyclonal human IgG.
60 minutes with gentle mixing every 10 minutes, after which
the liemolysis was stopped with 1.5 ml of cold PBS. The
optical density of the supernatants was analyzed at 412 nm
(0% and 100% controls were included in all assays).
For the inhibition assays, dilutions of RA sera that
had lbeen predetermined to give partial hemolysis (60430%)
were used. IgG was serially diluted and mixed in 0.1-ml
volumes with 0.1 ml of the predetermined dilutions of the RA
serum. The procedure was then performed as described for
the hemolytic assay.
RESULTS
RSC RF reactivity profiles. Table 1 lists the IgG
subclass proteins examined for RSC RF reactivities.
Figure 1 illustrates the inhibition of RSC RF-PFC
number and autologous serum RF hemolytic activity
by monomeric IgG preparations at 2 different inhibitor
concentrations. IgG3 generally produced inhibition of
RSC RF-PFC comparable with, and often greater
than, IgG1, although the differences in the mean
values were not significant. IgG2, in general, produced
less inhibition of RSC RF-PFC than did IgGl and
IgG31. IgG4 generally produced the least inhibition of
RSC RF-PFC. In contrast, autologous serum RF
showed greater reactivity with IgGl , IgG2, and IgG4,
but liittle or no reactivity with IgG3 when examined by
the liemolytic assay. Monomeric polyclonal human
IgG produced greater inhibition of RSC RF-PFC number and serum RF hemolytic activity than did any of
the individual subclasses. However, when the slopes
of inhibition were analyzed, IgG3 was the only IgG
preparation that produced significantly greater inhibition of RSC RF-PFC relative to serum RF hemolytic
activity. Therefore, relative to serum RF, RSC RF had
greater reactivity with IgG3 when examined by the
PI50 assay than did polyclonal human IgG and IgGl , 2 ,
and 4 subclasses.
Since the initial observations of RSC RF
reactivities were made on a limited number of IgG
subclass proteins (19, they required further investigation. Figure 2 shows the concentration-dependent inhibition of RSC RF-PFC number by 5 different IgG3
subclass proteins, compared with that produced by an
IgG1, IgG4, and polyclonal human IgG. The IgG3
subclass proteins inhibited as well, and in most cases,
better, than IgGl at all concentrations of added IgG,
although the differences in the mean values were not
significant. There was some variability in the degree of
inhibition produced by the individual proteins examined in RSC RF-PFC of different RA patients, but the
inhibitory profiles were consistently reproducible.
Figure 3 shows the inhibitory profiles of
polyclonal human IgG and monoclonal IgG1, IgG2,
and IgG3. The inhibition profile slopes for the IgG
subclasses were steeper than those for polyclonal
human IgG, which implies a greater homogeneity of
avidities of RSC RF molecules binding with the IgG
subclasses than with polyclonal human IgG (10,ll).
=2
-
100-
90-
C
0
aR
5
807060-
2
50-
3
40-
0
t
$
p
3020l0I
10
I
I
I
20
40
75
I
150
I
300
I
I
600
IgG ( W m l )
Figure 3. Concentration-dependent inhibition of synovial cell number produced by polyclonal human IgG and monoclonal IgGl, IgG2,
and IgG3. Error bars indicate 1 SD. RSC RF-PFC = rheumatoid
synovial cell rheumatoid factor plaque-forming cell.
*
ROBBINS ET AL
726
I
90
8ol
70-
C
8
T
0
50-
0
t
8
"I T
60-
r
5
901
- T
T
40-
20-
1
1 0 - 1= a
I -
0-
Number
IgG (500 pg/ml)
A
Number
IgG (330 pg/ml)
B
Figure 4. Comparison of polyclonal human IgG with human IgGl, IgG2, IgG3, and IgG4 as inhibitors of synovial cells, as measured by plaque
number and plaque volume. Plaque assay conditions and the estimation of plaque volume were as described in Materials and Methods. A and
B represent RSC derived from 2 rheumatoid arthritis patients. Specimens were examined using different IgG subclass proteins. Cd3 = plaque
volume (sum of the RSC RF-PFC diameters cubed). Each assay was done in duplicate. Results from 3 other RSC donors were similar. Error
bars indicate 1 SD. RSC RF-PFC = rheumatoid synovial cell rheumatoid factor plaque-forming cell; Hu = polyclonal human IgG.
Relative avidities of RSC RF for monomeric
human IgG and IgG subclasses. Recent observations
suggest that inhibition of plaque volume (Ab50) is a
better method for estimating the relative affinitiedavidities of antibodies detected in PFC assays than
is the PI50 assay (10,ll). Plaque volume expressed as
percent of control (uninhibited) reflects the amount of
free antibody, as opposed to that bound by inhibitory
antigen. We used this method to estimate the relative
avidity of RSC RF for monomeric polyclonal human
IgG and monoclonal IgG subclasses by calculating the
sum of the RSC RF-PFC diameters cubed (Zd3) as a
measure of residual unbound RF. Figures 4A and B
compare the inhibitory profiles for polyclonal human
IgG and IgG subclasses 1 4 for both RSC RF-PFC
number and volume. In both cases, the inhibitory
effects were comparable and consistent with previous
observations. However, inhibition of RSC RF-PFC
volume was significantly greater than inhibition of
RSC RF-PFC number, demonstrating more bound RF
than simple enumeration of RSC RF-PFC would indicate. These results demonstrated that plaque number
and plaque volume are different measures of inhibition, and that plaque volume appears to be a more
sensitive measure of RSC RF inhibition by competing
antigens.
Figure 5 compares the inhibitory effects of 5
IgG3 subclass proteins with those of IgG1, IgG4, and
polyclonal human IgG. Interestingly, the IgGl generally produced more inhibition of RSC RF-PFC number than did IgG3. However, the opposite effect was
seen when inhibition of RSC RF-PFC volume was
19s IgM RF AVIDITY
727
T
T
r
L
Number
Bd
IgG (1000 pg/ml)
Figure 5. Comparison of 5 IgG3, an IgGl, and an IgG4 as inhibitors
of synovial cell number and volume. Results from 2 other RSC
donors were similar. Error bars indicate 1 SD. RSC RF-PFC =
rheumatoid synovial cell rheumatoid factor plaque-forming cell; Hu
= polyclonal human IgG.
calculated. Also, inhibition of plaque volume was
greater than inhibition of plaque number. In this
instance, IgG4 and IgGl inhibited equally as well,
which was unusual. Thus, a substantial uumber of
RSC RF molecules bound with IgG3 andsaight have
higher avidity for IgG3 than for IgG1, and more so
than reflected by inhibition of PFC number.
Plaque diameter as a measure of relative avidity
of RSC RF for human IgG, IgG1, and IgG3. Plaque
diameter was used as another way of estimating relative avidity of RF detected in the RSC RF-PFC
assay .Plaques of larger diameter will contain higher
avidity antibody than do smaller diameter plaques if
antibody concentrations are the same (10). We examined the inhibitory effect of polyclonal human IgG,
IgG1, and IgG3 on RSC RF plaque diameters, since
they consistently produced more inhibition of the RSC
RF-PFC assay than did IgG2 or IgG4. The results are
expressed in Figure 6 . All inhibitor proteins inhibited
both large and small plaques. Polyclonal human IgG
produced the greatest inhibition of both large and
small plaques, followed by IgG3 and IgG1, in that
order. However, IgG3 produced almost equivalent
inhibition of large diameter plaques as did polyclonal
human IgG. Polyclonal human IgG inhibited a larger
number of small diameter plaques than did IgG3,
which accounted for its greater inhibition of PFC
number and plaque volume. IgGl actually inhibited a
greater number of RSC RF-PFC at the lower concentration of added antigen than did IgG3, but the ma-
L
L
/o( n
n
CONTROL
RSC RF-PFC Diameter (mm)
A
B
Figure 6. Size selectivity of the inhibition of synovial cell plaque diameter by polyclonal humah IgG, IgG1, and IgG3 subclasses (A) and in
controls (B). These results are representative of RSC from 3 different donors, which were examined in this way using 2 different examples of
IgGl and IgG3. RSC RF-PFC = rheumatoid synovial cell rheumatoid factor plaque-forming cell.
728
ROBBINS ET AL
jority of the RSC RF-PFC inhibited were of small
diameter, whereas IgG3 preferentially inhibited large
diameter RSC RF-PFC. Thus, it appears that IgG3
inhibited high avidity RSC RF as well as did polyclonal
human IgG, and the better overall inhibitory effect of
polyclonal human IgG was the result of its greater
ability to inhibit low avidity RSC RF.
DISCUSSION
Previous observations have indicated a selective deficiency in serum RF compared with RF detected in a PFC assay using PBMC from RA patients.
For example, RF-PFC have greater reactivity with
human IgG than with rabbit IgG, in contrast with
autologous serum RF (9). The results of this study
further indicate a selective deficiency in serum RF
reactivity compared with RF synthesized by autologous RSC. In particular, many RSC RF molecules
have reactivity with human subclass IgG3 relative to
autologous serum RF, and many of these RSC RF
moltxules appear to have higher avidity for IgG3 than
RSC RF binding with IgG1. These observations were
made with a number of different IgG subclass proteins
in the RF-PFC assay, using RSC from a number of
different RA donors. Moreover, it appears that the
RSC R F reactivity with IgG3 is consistent for
antigenic determinants common to many, if not all,
IgG3 subclasses. This is in definite contrast with serum
RF, in which the lack of reactivity with IgG3 has been
well documented by other investigators (5,6).
Although polyclonal human IgG quantitatively
produced greater inhibition of RSC RF-PFC than did
the IgG subclasses, the inhibitory slopes for the IgG
subclasses were steeper, which suggests greater homogeneity of the RSC RF molecules binding with the IgG
subclasses, as compared with polyclonal human IgG
(10,ll). This is consistent with the polyclonal nature of
human IgG and the monoclonal character of the human IgG subclasses. Because both human IgG and RF
are polyclonal products, there are a greater number of
antigenic determinants present on polyclonal IgG molecules and a greater number of antibody-combining
sites for those various antigenic determinants on
polyclonal RF molecules. This is in contrast with the
tgG subclasses which are monoclonal proteins, and, as
such, have more limited antigenic repertoires to
present to the RF.
High avidity antibody produces a hemolytic
plaque of larger diameter than low avidity antibody if
the antibody concentrations are the same, and the
addition of competing antigen results in a greater
reduction in the area of high avidity plaques compared
with low avidity plaques (11,12). Diversity of plaque
diameters is a consistent feature of plaque assays and
reflects differences in the amount, avidity, and hemolytic efficiencies of antibodies secreted by individual
PFC. If equivalent hemolytic efficiencies exist between antibody classes, inhibition of plaque number
will depend on 2 factors: the amount of antibody
secreted and the avidity of the antibody. Thus, PI50
determined from plaque enumeration is influenced by
both of these factors, and cannot be taken as a
rigorous measure of avidity of the antibody for the
competing antigen. In contrast, the percent inhibition
of total plaque volume provides a measure of the ratio
of free to bound antibody; this is independent of the
amount of antibody secreted by the PFC. Ab50, therefore, is a theoretically more sound measure of the
avidity of the secreted antibody for the inhibiting
antigen. These considerations have previously been
emphasized by DeHeer and Edgington (10).
In the present study, we have measured the
diameters of individual RSC RF-PFC to assess the
relative concentration of free RF. By calculating the
percent inhibition of secreted RF, we have obtained a
measure of the ratio of free to bound RF, which should
allow comparison of the results of RF-PFC inhibition
assays independent of the number of RSC secreting
RF, the total RF concentration, or the difference in RF
secreted by different RSC (10). Our observation that
IgG3 and polyclonal IgG preferentially inhibited the
large diameter plaques, in contrast with the inhibition
seen by IgGl, IgG2, and IgG4, is of interest. There are
2 possible explanations for this behavior: 1) IgG3reactive antibody is secreted in greater quantity from
individual PFC than is antibody reactive toward the
other subclasses; and 2) IgG3-reactive antibody has a
higher avidity or hemolytic efficiency for sensitized
SRBC than do the antibodies reactive toward the other
subclasses. There is no reason to expect, a priori, that
cells producing IgG3-reactive RF do so in greater
amount; thus, the first possibility is not very likely.
The more probable explanation is the second one, that
IgG3-reactive RF species are high avidity antibodies.
This may have important pathogenic consequences in
RA, as discussed below. This observation and the
slopes of the inhibition profiles support our interpretation that the greater inhibition of RSC RF produced
by polyclonal human IgG, compared with the IgG
subclasses, is indeed due to its polyclonality.
Because RSC RF is also polyclonal, it is possi-
19s IgM RF AVIDITY
ble that RSC R F with primary reactivity for IgG3 may
also be inhibited by determinants on IgGl, for which it
has lower avidity and with which it cross-reacts. The
same could apply to RSC RF, which has primary
reactivity for IgG 1 but which cross-reacts with determinants on IgG3. Thus, the amount of RSC R F that
reacts with IgG3 may actually be greater than the data
indicate. However, if this were the case with serum
RF, one would expect to see the same inhibitory
profiles seen with RSC RF. R F with this reactivity is
clearly absent from autologous serum RF.
These observations may relate to RF’s pathogenic importance in RA. For example, it is possible
that high avidity RSC RF, upon release from RSC,
complex immediately with IgG3 produced locally,
activate complement, and produce immune complex-mediated tissue injury in situ. This could explain
the deficiency of R F in autologous serum with specificity for IgG3. In this regard, IgG3 is preferentially
synthesized in RSC, compared with autologous serum
and normal lymphoid tissue (17), and the presence of
RF-PFC in PBMC correlates with aggressive synovitis
and active vasculitis in RA (2).
Therefore, RSC R F reactivity with IgG3 appears to be for shared determinants common to many,
if not all, IgG3 molecules. Moreover, the avidity of
RSC R F that reacts with IgG3 appears to be higher
than RSC R F that reacts with the other IgG subclasses. Further, IgG3-specific RSC R F may have
greater pathogenic importance than serum RF. The
specific antigenic determinants for RSC R F on the
IgCi3 molecule are unknown; however, better characterization of them may improve our understanding of
the inflammatory events in RA.
ACKNOWLEDGMENTS
The authors greatly appreciate the expert technical
assistance of Thomas Kenny and Carole Cole, and the
secretarial assistance of Nikki Rojo. We also thank Dr.
Malcolm MacKenzie for providing us with IgG subclass
proteins.
REFERENCES
1. Carson DA: Rheumatoid factor, Textbook of Rheumatology. First edition. Edited by WN Kelley, ED Harris
Jr, S Ruddy, CB Sledge. Philadelphia, WB Saunders,
1981, pp 677-688
729
2. Vaughan JH, Chihara T, Moore TL, Robbins DL,
Tanimoto K, Johnson JS, McMillan R: Rheumatoid
factor producing cells detected by direct hemolytic
plaque assay. J Clin Invest 58:933-941, 1976
3. Normansell DE: Anti-gammaglobulin rheumatoid arthritis sera. I. Studies on the 22s complex. Immunochemistry 7:787-797, 1970
4. Eisenberg R: The specificity and polyvalency of binding
of a monoclonal rheumatoid factor. Immunochemistry
13~355-359, 1976
5. Normansell DE, Young CW: The IgG subclass specificity of anti-IgG immunoglobulin rheumatoid factor.
Immunochemistry 12: 187-188, 1975
6. Henney CS: Structural and conformational specificity of
the antigen for rheumatoid factor. Ann NY Acad Sci
1685242, 1969
7. Minga UM, Segre M, Segre D: Numbers and avidity of
anti-DNP antibody plaques in different inbred mouse
strains. Immunogenetics 2:377-379, 1975
8. Anderson B: Studies on the regulation of avidity at the
level of the single antibody-forming cell. J Exp Med
132:77-88, 1970
9. Robbins DL, Moore TL, Carson DA, Vaughan JH:
Relative reactivities of rheumatoid factors in serum and
cells: evidence for a selective deficiency in serum rheumatoid factor. Arthritis Rheum 21:820-826, 1978
10. DeHeer DH, Edgington TS: Estimation of relative antibody affinity at the level of the antibody-secreting cell
during maturation of the immune response. Cell Immunol 18:466475, 1975
11. DeHeer DH, Edgington TS: Relationship between antibody affinity and hemolytic plaque diameter. 1. Purified
anti-DNP antibody. J Immunol 122:980-983, 1979
12. DeHeer DH, Edgington TS: Relationship between antibody affinity and hemolytic plaque diameter. 11. Maturation of primary immune responses to DNP and SRBC.
Mol Immunol 17:1231-1236, 1980
13. 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
14. Taylor-Upsahl MM, Abrahamsen TG, Natvig JB: Rheumatoid factor plaque-forming cells in rheumatoid
synovial tissue. Clin Exp Immunol 28: 197-203, 1977
15. Robbins DL, Wistar R Jr: Comparative specificities of
serum and synovial cell 19s IgM rheumatoid factors in
rheumatoid arthritis. J Rheumatol 12:437443, 1985
16. Carson DA, Lawrence S, Catalan0 MA, Vaughan JH,
Abraham G: Radioimmunoassay of IgG and IgM rheumatoid factors reacting with human IgG. J Immunol
119~295-300, 1977
17. Hoffman WL, Goldberg MS, Smiley JD: Immunoglobulin G3 subclass production by rheumatoid synovial tissue cultures. J Clin Invest 69:13&144, 1982
Документ
Категория
Без категории
Просмотров
2
Размер файла
699 Кб
Теги
19s, avidity, secreted, subclass, human, cells, factors, igm, relative, igg, estimating, synovial, rheumatoid
1/--страниц
Пожаловаться на содержимое документа