Production of antibodies specific for Fc, Fab', and streptokinase-streptodornase in vitro by peripheral blood cells from patients with rheumatoid arthritis and normal donors. Identification of immune complexes in culture supernatants containing hidden antibodies reactive with Fab' fragments of immunoglobulin G

Autoantibodies as chameleons

Autoantibody determinations are frequently used by rheumatologists to establish the diagnosis or assess follow up clinical status in patients with connective tissue diseases. Such autoantibodies are often presumed to have harmful effects, particularly since some such as anti-native DNA or anti-Ro have frequently been related to tissue damage or to functional impairments. However, there are many other autoantibodies which react with antigenic components of normal autologous tissues which have not been demonstrated to have self-damaging or harmful effects. Some of these autoantibodies may actually represent natural built-in mechanisms of feed-back inhibition, serving to modulate normal physiologic function. Autoantibodies may be compared to chameleons since their function or quality is often judged by the company they keep or by their anatomical localization. Since many autoantibodies to intra-cellular products seem to react with active sites of important biologic molecules, they may provide us with a much sharper image of a number of natural cellular functions.

Characterization and V(H) sequences of human monoclonal anti-F(ab')(2) autoantibodies from normals and Sjögren's syndrome patients

To investigate the genetic background of anti-F(ab')(2) autoantibodies and the mechanism behind their production we have analyzed 10 human monoclonal antibodies directed against IgG F(ab')(2) and IgG Fab. They were all derived from peripheral blood by the EBV/hybridoma technique. Eight were from three healthy individuals and two from two patients with primary Sjögren's syndrome (pSS). They react with epitopes on distinct regions of IgG, including epitopes present on or near the hinge of IgG, epitopes on the Fd gamma, and an antigenic determinant(s) present on lambda light chains. These determinants are either exposed on the intact IgG molecule or revealed following pepsin or papain digestion. The V(H) germline gene repertoire used is diverse and with considerable overlap with that used by rheumatoid factors (RF). The two IgG antibodies from normals are extensively mutated (13 and 24 mutations/V(H)), but with a replacement to silent mutation ratio in the CDR(H)1 + 2 of only 3.7. The IgM antibodies from normals are also heavily mutated (mean 10 mutations/V(H)). This suggests that anti-F(ab')(2) from normals are generated by an antigen-driven somatic hypermutation mechanism. In contrast, the two IgM antibodies from pSS are virtually unmutated in both V(H) and V(L). Together with published data of pSS RF and anti-Ro 52-kDa sequences (1-3), this suggests that there is an expanded population of naïve B cells with autoantibody specificities in the peripheral blood of pSS patients.

Induction of an anti-Fab, anti-DNA and anti-RNA polymerase I autoantibody response network in rabbits immunized with SLE anti-DNA antibody

Systemic lupus erythematosus (SLE)-like anti-IgG Fab autoantibodies (autoAb) were induced in rabbits by immunization with either human, mouse or rabbit anti-DNA Ab. In direct-binding radioimmunoassay (RIA), affinity-purified anti-normal rabbit (NR) Fab autoAb cross-reacted with normal mouse (NM) Fab, ssDNA (but not dsDNA), poly(dA,dT), and RNA polymerase I (RPI). Affinity-purified anti-NM IgG Ab isolated from the same antisera cross-reacted with NR Fab, ssDNA and RPI. In inhibition RIA, soluble NR Fab inhibited anti-NR Fab binding to NR Fab and ssDNA, but enhanced binding to RPI. In contrast, ssDNA or RPI inhibitors had no effect upon autoAb binding to NR Fab. Anti-DNA, anti-RPI and anti-RPI 190 kD subunit autoAb, induced by immunization with lupus mouse anti-DNA Ab, also reacted with NM Fab, but were idiotypically specific for lupus mouse anti-DNA Fab. Further, rabbit anti-DNA and anti-RPI IgG autoAb, induced by immunization with rabbit anti-DNA IgG, were each idiotypically specific for homologous and autologous rabbit anti-ssDNA Fab. Together, these data provide evidence that anti-DNA, anti-RPI and anti-Fab autoAb are linked in a complex, multiple-specific and perhaps regulatory, immune response idiotype network in SLE.

IgG binding of monoclonal anti-nuclear antibodies from MRL-lpr/lpr mice

To assess the specificity of anti-nuclear antibodies with cross-reactive rheumatoid factor (RF) activity, monoclonal anti-DNA and anti-Sm antibodies from MRL-lpr/lpr mice were tested for binding to a variety of IgG antigens. These antibodies had all been previously identified as binding heterologous IgG. By ELISA, antibodies in this panel all bound BALB/c myeloma proteins representing the different IgG subclasses, indicating broad reactivity with murine IgG as well as heterologous IgG. The determinant recognized by these antibodies was further investigated using the Fab, F(ab')2 and Fc fragments of both human as well as rabbit origin. All antibodies bound well to fragments as well as intact IgG antigens. These antibodies were further analysed by Western blotting, demonstrating that most bound to both heavy and light chains of human origin. Together, these observations suggest that some anti-nuclear antibodies bind a conserved antigenic determinant present widely on immunoglobulin chains. This determinant may represent a common sequence important in immunoglobulin domain structure.

Induction and immunochemical properties of a novel anti-antibody

This paper describes results which characterize an induced antibody in normal outbred rabbits which we have, for convenience, called parareactant (PR). PR resulting from autoimmunization of rabbits with either keyhole limpet hemocyanin-anti-tetanus toxoid F(ab')2 or with tetanus toxoid-anti-tetanus toxoid F(ab')2 complexes was studied. PR activity was directed solely to autologous, homologous or heterologous F(ab')2 fragments regardless of their specificity. PR failed to react with intact antibodies or with antigen-antibody complexes consisting of homologous antibody bound to specific antigen. Radioimmunoassay and ELISA inhibition assays showed that reactivity between PR and autologous anti-tetanus toxoid F(ab')2 or homologous anti-bovine serum albumin F(ab')2 fragments was specifically inhibited with antigen. Anti-allotypic antibodies specific for a2 and b6 markers strongly inhibited binding of 125I-anti-micrococcal carbohydrate F(ab')2 (a2, b6) with PR (a3, b4, b5). PR specificity thus appears to be directed against non-idiotypic determinants present in Fv regions. Affinity immunoblotting was used to analyze clonality of PR in the sera collected from individual rabbits during the course of an active immune response. PR-positive sera displayed clonally restricted spectrotype patterns. PR molecules were predominantly IgG with isoelectric points of 5.9-6.8. These results strongly suggest that these PR molecules are coded by a small number of V region genes.

Demonstration of anti-idiotypic antibodies directed against IgM rheumatoid factor in the serum of rheumatoid arthritis patients

We have identified the presence of anti-idiotypic activity against IgMRF in the sera of RA patients. Only patients seropositive for IgMRF had significant levels of anti-idiotypic activity, while seronegative patients and normal volunteers did not. When this anti-idiotypic activity was affinity-purified from a single RA patient, two separate binding activities were identified. IgG antibodies were pepsin-digested to F(ab')2 fragments before affinity-purification to remove the Fc portion capable of binding to IgMRF. Anti-idiotypic F(ab')2 fragments of IgG were eluted from an IgMRF-Sepharose 4B column. These F(ab')2 bound preferentially to IgMRF bearing an idiotype recognized by the anti-idiotypic murine monoclonal 17.109. A second anti-idiotypic F(ab')2 was affinity purified using rabbit anti-human Fc antibody bound to Sepharose 4B. These eluted antibodies behaved as the internal image of IgG, binding five out of seven IgMRF's tested. The binding of both anti-idiotypic F(ab')2 was inhibited with human IgG. The presence of both IgMRF and anti-idiotypic antibodies directed against it in the sera of RA patients suggests that anti-idiotypic antibodies alone are not capable of inhibiting the production of rheumatoid factor.

Recognition by anti-Fab antibodies in rheumatoid arthritis of structure(s) widely distributed on human Fab molecules

Anti-Fab antibodies (aFABA) of restricted clonality and acidic spectrotypes were isolated from the sera of patients with rheumatoid arthritis (RA). These aFABA reacted with multiple populations of pooled human Fab molecules, which had been charge separated by chromatofocusing techniques (CF), indicating that the structures recognized by these aFABA were present on a polyclonal population of Fab molecules. The structures were also widely distributed among the Fab repertoires of normal individuals, as well as individual autologous and heterologous RA patients. Thus, the aFABA did not appear to recognize highly restricted epitope(s), i.e. a private idiotope, limited in its expression to RA individuals. The determinants of the Fab molecules recognized by affinity purified aFABA could be defined by linear and/or conformational structures, depending upon the individual from which the aFABA were isolated. Additionally, some of the affinity purified aFABA also reacted with Fc fragments, suggesting the presence of epibody-like autoantibodies in this population. Lastly, size analysis of the circulating IgG4 aFABA complexes indicated that these autoantibodies were not complexed with intact IgG, but rather with a molecule of 40-60 kDa, further suggesting the potential for these autoantibodies to react with multiple antigens.

Acute rheumatoid factor positive (IgM) polyarthritis associated with a Klebsiella pneumonitis

The authors report a case of a patient suffering from acute polyarthritis with a high rheumatoid factor titre, associated with a Klebsiella pneumonitis. A polyclonal B lymphocyte activation or a possible cross reaction between rheumatoid factor and an antigen related to Klebsiella may explain the elevated production of rheumatoid factor observed.

Mechanism of complement activation after coronary artery occlusion: evidence that myocardial ischemia in dogs causes release of constituents of myocardial subcellular origin that complex with human C1q in vivo

To evaluate whether ischemic myocardium releases molecules that react with the first component of complement, we studied cardiac lymph from eight dogs before and at intervals after coronary artery occlusion and reperfusion. Before occlusion, the dogs were injected intravenously with radiolabeled human C1q. Labeled C1q could be detected in the cardiac lymph within minutes following injection. Rabbit antisera, prepared against substances precipitated from postreprefusion cardiac lymph by anti-human C1q, also reacted with specific constituents of isolated cardiac sarcoplasmic reticulum and mitochondria. To evaluate whether mitochondria are the source of these C1q-binding proteins, we isolated intramyofibrillar and subsarcolemmal mitochondria from canine heart and incubated sonicates of these with purified C1q, immobilized on nitrocellulose. Molecules bound to the immobilized C1q were removed with 0.1% sodium dodecyl sulfate, fractionated under reducing conditions by polyacrylamide gel electrophoresis, and transferred electrophoretically to nitrocellulose paper. Antisera prepared against postreperfusion lymph reacted with a 31,000-32,000-dalton protein in these nitrocellulose paper replicas. Since this protein originates from mitochondria, binds to C1q, and is recognized by antibodies made against postreperfusion lymph, this protein is likely to be one of the subcellular constituents that, upon release from ischemic cells, activates the complement cascade. To evaluate the clinical relevance of these observations, we tested sera from 53 patients obtained 48-72 hours after hospitalization for suspected myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Human immune response to allergens of house dust mite, Dermatophagoides pteronyssinus. IV. Occurrence of natural autologous anti-idiotypic antibodies

IgG isolated from the plasma of seven individuals hypersensitive to the common house dust mite Dermatophagoides pteronyssinus (DPT) was exhaustively adsorbed onto insolubilized DPT. The unbound fraction was found by radioimmunoassay to contain antibodies recognizing the variable region of both anti-DPT IgG and IgE antibodies. This recognition was idiotype (Id)-specific as it persisted after passage over insolubilized polyclonal IgG of unrelated specificity. Most of these anti-Id IgG carried the internal image of the initial antigen in that they competitively inhibited the binding of anti-DPT antibodies to DPT. Immunoadsorption of anti-Id IgG onto insolubilized anti-DPT IgG antibodies from the same individual completely eliminated their reaction with anti-DPT IgG but not with anti-DPT IgE, suggesting that idiotopes included in the antigen-binding site of specific IgG and IgE antibodies were not identical. Anti-Id IgG recognizing idiotopes located outside the antigen-binding site (bystander idiotopes) were also completely removed by passage over insolubilized anti-DPT IgG; in this case the reaction of the anti-Id IgG with both anti-DPT IgG and anti-DPT IgE was inhibited, indicating that, for a given individual, bystander idiotopes were shared between anti-DPT antibodies pertaining to these two isotypes.

Spontaneous immunoglobulin synthesis by peripheral mononuclear cells in active rheumatoid arthritis

Spontaneous production of immunoglobulins (Igs) by peripheral blood mononuclear cells (PBMC) in vitro was investigated to assess B cell activity in a group of 24 patients with rheumatoid arthritis (RA) with or without active joint disease and with or without rheumatoid vasculitis (RV) at the time of study. PBMC of patients with active arthritis (Ritchie index above 16) produced significantly more IgG and IgA than those of patients with inactive joint disease or those of 12 healthy controls. Enhanced production of IgG was found mainly among RA patients with concomitant RV, whereas markedly enhanced IgA production could also be found in patients without symptoms of RV. IgM production was only enhanced in two patients who had both active arthritis and RV. High production of IgG and IgA was probably due to increased numbers of Ig-secreting cells among freshly isolated PBMC, since the concentrations of Ig produced in vitro rose steadily, starting on day 0 and persisting throughout the entire culture period. Moreover, IgG and IgA concentrations measured after 7 days of culture showed significant correlations with the numbers of IgG- and IgA-containing plasma cells in PBMC on day 0. Comparison of the spontaneous production of Igs by PBMC with the levels of circulating immune complexes (CIC), showed that CIC levels were also significantly higher in active arthritis and in RV, but that there was no correlation between the CIC levels in individual patients and Ig production by their PBMC in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

IgG and IgM rheumatoid factor synthesis in rheumatoid synovial membrane cell cultures

The detection of rheumatoid factors (RFs) in synovial membranes and fluids of patients with rheumatoid arthritis (RA) has suggested that local production of these antiimmunoglobulin autoantibodies may have a role in the pathogenesis of synovitis. To quantitate RF synthesis in the rheumatoid synovial membrane, 12 synovial specimens were obtained from patients with seropositive RA, 5 from patients with seronegative RA, and 6 from patients with other arthritides. Single cell suspensions were cultured, and supernatants were analyzed for IgG, IgM, IgG-RF, and IgM-RF by solid-phase radioimmunoassays. IgM-RF was detected in all of the 12 seropositive culture supernatants, and IgG-RF was detected in 8 of the 12. Addition of cycloheximide to the cultures resulted in a greater than or equal to 40% decreased in the amount of IgM-RF. A similar decrease in IgG-RF occurred in the 4 cultures in which the largest amounts of IgG-RF were detected. IgM-RF synthesis represented 7.3 +/- 0.7% (mean +/- SEM) of the total IgM produced, and IgG-RF represented 2.6 +/- 1.1% (mean +/- SEM) of the IgG synthesized in those cultures with detectable IgG-RF. Cultures of synovial membrane cells (SMC) from seronegative RA patients or patients with other arthritides did not contain detectable amounts of IgM-RF or IgG-RF. Selective synthesis of RF by seropositive synovium was suggested by the observation that the fractions of synthesized IgM with RF activity were greater in the SMC supernatants than in paired sera in all cases, and the fractions of IgG with RF activity were greater in the SMC supernatants of 3 of the 4 cases in which substantial amounts of IgG-RF were produced. Comparison of the percentages of newly synthesized IgM with RF activity in paired cultures of SMC and peripheral blood mononuclear cells similarly indicated selective synthesis of IgM-RF by the synovium. These results demonstrate active and selective synthesis of both IgG-RF and IgM-RF by seropositive SMC. However, RFs account for only a minor fraction of the total Ig produced.

Studies of anti-F(ab')2 antibodies and possible immunologic control mechanisms in systemic lupus erythematosus

Studies of anti-DNA and anti-F(ab')2 antibodies were performed by enzyme-linked immunosorbent assay in 51 patients with systemic lupus erythematosus (SLE). Patients with severe, uncontrolled disease showed high levels of anti-DNA and low levels of anti-F(ab')2 antibodies. Patients with quiescent SLE usually showed high levels of anti-F(ab')2 and low levels of anti-DNA antibodies. Isolated anti-F(ab')2 antibodies from autologous SLE remission serum or from the sera of unaffected siblings of SLE patients showed maximum inhibition in test systems using affinity-purified SLE anti-DNA antibodies reacting with single-stranded DNA.

Differential inhibition of protein synthesis: a possible biochemical mechanism of thalidomide teratogenesis

A theory concerning the chemical and biochemical mechanisms of thalidomide teratogenesis is presented. A considerable body of evidence suggests that the glutarimide ring of thalidomide may exert its biological activity because of its resemblance to the imide pyrimidines thymine and uracil. In addition to the glutarimide ring, thalidomide contains a moderately reactive phthalimide moiety, which allows the spontaneous formation of various glutarimide derivatives in fetal tissues. A model is proposed in which the phthalimide group reacts with small nucleophiles, most likely the polyamines, to produce a derivative(s) having a similar biochemical potential to that of cycloheximide, a glutarimide which is a powerful inhibitor of the elongation phase of protein synthesis. Interference in the elongation phase results in the selective inhibition of the translation of messages which have a high translational efficiency. Evidence is reviewed concerning the differential inhibition or protein synthesis by cycloheximide and the effects of this inhibition on various biochemical and biological processes which are critical during development and differentiation. A similar biochemical activity by the putative thalidomide derivative(s) could explain its extreme teratogenic potential. A number of parallels between the biological effects of thalidomide and cycloheximide are discussed which support the idea that a similar biochemical activity is involved. The theory readily explains many of the observed biological effects of thalidomide including the large difference between fetal and adult toxicity. In addition, evidence is reviewed which suggests that the teratogenic properties of a number of drugs which are structurally related to thalidomide may have a common chemical basis due to the similarity of their imide core structures to thymine and uracil.

Anti-Fab' antibodies in rheumatoid arthritis. Measurement of the relative quantities incorporated in soluble immune complexes in sera and supernatants from cultured peripheral blood lymphocytes

High levels of anti-immunoglobulins that react with Fab' fragments of IgG have been observed in sera of patients with rheumatoid arthritis (RA). To determine how much of these anti-Fab' antibodies are incorporated within immune complexes (IC), we added 125I-Fab' to sera and then measured the amount of labeled Fab' that could be precipitated by adding polyethylene glycol (PEG). Sera were either maintained at neutral pH during this procedure or acidified (pH 3) to dissociate IC. Acidification permitted the 125I-Fab' an equal chance to compete with other endogenous antigens for anti-Fab' antibodies, once excess hydrogen ion was removed. Quantities of anti-Fab' in sera of 20 seropositive RA patients were greater than in sera of 43 age- and sex-matched healthy controls, as measured by this assay and by a solid phase radioimmunoassay. However, significantly less anti-Fab' antibody was incorporated in ICs in the RA patients' sera. Supernatants from cultured peripheral blood lymphocytes of RA patients also contained relatively more "free" and less "hidden" anti-Fab' than culture supernatants from controls. Thus there appear to be qualitative as well as quantitative differences in the anti-Fab' antibodies synthesized by RA patients. This may reflect different proportions of IgM and IgG anti-Fab' in their sera, differences in the average avidity of these antibodies, or differences in the reciprocal relationships within the idiotypic network that result in release of antibodies by certain antibody-producing cells, but not by clones that produce complementary idiotypes.