Rheumatoid factor, complement, and conglutinin aberrations in patients with subacute bacterial endocarditis

Rethink About the Role of Rheumatoid Factor and Anti-citrullinated Protein Antibody in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by joint inflammation and extra-articular manifestations. Many questions in the pathogenesis, clinical manifestation, and disease spectrum are answered after the discovery of the first autoantibody namely rheumatoid factor (RF). The finding of the second autoantibody named anti-citrullinated protein antibody (ACPA), which unearths the importance of protein citrullination process. It further provides the insight how immune cells and complement interact to perpetuate the inflammatory response. These two autoantibodies pave the way for our better understanding of RA. This review article focuses on the history, pathophysiology, and clinical association of these two autoantibodies in RA.

Autoantibodies in the Pathogenesis, Diagnosis, and Prognosis of Juvenile Idiopathic Arthritis

Autoantibody production occurs in juvenile idiopathic arthritis (JIA) and numerous other autoimmune diseases. In some conditions, the autoantibodies are clearly pathogenic, whereas in others the roles are less defined. Here we review various autoantibodies associated with JIA, with a particular focus on antinuclear antibodies and antibodies recognizing citrullinated self-antigens. We explore potential mechanisms that lead to the development of autoantibodies and the use of autoantibody testing in diagnosis and prognosis. Finally, we compare and contrast JIA-associated autoantibodies with those found in adults with rheumatoid arthritis (RA).

Historical observations contributing insights on etiopathogenesis of rheumatoid arthritis and role of rheumatoid factor

When studies on rheumatoid arthritis (RA) that were made many decades ago and could be considered "historical" in nature are analyzed in the context of recent observations, important insights on RA and on the function of rheumatoid factor (RF) become apparent. RF in the role of antibody to immune complexes (ICs) appears to be involved in activation of the complement system and in the production of chemotactic and inflammatory mediators, creating a condition that can be sustained and reinitiated. In the synovial cavity, a state of nonresolving inflammation is produced with the formation of citrullinated protein antigen-antibody complexes or other forms of ICs. This is followed by a second wave of IC production in the form of RF acting as antibody reactive with the initial ICs. Both of these processes are associated with complement consumption and production of inflammatory mediators. We present a model of an initiation phase of RA that might represent an example of repetitive formation of ICs and complement-mediated inflammation. Targeting therapy at this phase of RA to break the cycles of recurrent inflammation might be a novel approach to aid in further control of the disease.

Glomerular disease in patients with infectious processes developing antineutrophil cytoplasmic antibodies

To identify differences in treatment and outcome of various types of glomerulonephritis developing in the course of infections triggering antineutrophil cytoplasmic antibody (ANCA) formation, we analyzed published reports of 50 patients. Immunosuppressives were added to antibiotics in 22 of 23 patients with pauci-immune glomerulonephritis. Improvement was noted in 85% of 20 patients with information on outcomes. Death rate was 13%. Corticosteroids were added to antibiotics in about 50% of 19 patients with postinfectious glomerulonephritis. Improvement rate was 74%, and death rate was 26%. Two patients with mixed histological features were analyzed under both pauci-immune and post-infectious glomerulonephritis categories. In 9 patients with other renal histology, treatment consisted of antibiotics alone (7 patients), antibiotics plus immunosuppressives (1 patient), or immunosuppressives alone (1 patient). Improvement rate was 67%, permanent renal failure rate was 22%, and death rate was 11%. One patient with antiglomerular basement disease glomerulonephritis required maintenance hemodialysis. Glomerulonephritis developing in patients who became ANCA-positive during the course of an infection is associated with significant mortality. The histological type of the glomerulonephritis guides the choice of treatment. Pauci-immune glomerulonephritis is usually treated with addition of immunosuppressives to antibiotics.

Autoimmunity in Rheumatic Diseases Is Induced by Microbial Infections via Crossreactivity or Molecular Mimicry

A general consensus supports fundamental roles for both genetic and environmental, mainly microbial, factors in the development of autoimmune diseases. One form of autoimmune rheumatic diseases is confined to a group of nonpyogenic conditions which are usually preceded by or associated with either explicit or occult infections. A previous history of clinical pharyngitis, gastroenteritis/urethritis, or tick-borne skin manifestation can be obtained from patients with rheumatic fever, reactive arthritis, or Lyme disease, respectively, whilst, other rheumatic diseases like rheumatoid arthritis (RA), ankylosing spondylitis (AS), and Crohn's disease (CD) are usually lacking such an association with a noticeable microbial infection. A great amount of data supports the notion that RA is most likely caused by Proteus asymptomatic urinary tract infections, whilst AS and CD are caused by subclinical bowel infections with Klebsiella microbes. Molecular mimicry is the main pathogenetic mechanism that can explain these forms of microbe-disease associations, where the causative microbes can initiate the disease with consequent productions of antibacterial and crossreactive autoantibodies which have a great impact in the propagation and the development of these diseases.

Symptomatic anti-neutrophil cytoplasmic antibody-positive disease complicating subacute bacterial endocarditis: to treat or not to treat?

A 54-year-old man was diagnosed with Streptococcus mutans endocarditis of the mitral valve. Serological tests disclosed the presence of multiple autoantibodies including c-ANCA, anti-PR3 and anti-MPO. While the fever subsided with antibiotics, mental status and renal function deteriorated rapidly. Kidney biopsy revealed pauci-immune glomerulonephritis and acute eosinophilic interstitial nephritis. The abnormal clinical features improved rapidly after addition of corticosteroids and cyclophosphamide to the antibiotics. Immunosuppressive agents may be required in a fraction of the patients with infective endocarditis who develop ANCA and ANCA-mediated renal disease. Histological identification of the type of renal disease is imperative for the choice of the treatment.

Rheumatoid factor by laser nephelometry and Waaler–Rose assay: prognostic value in patients with recent‐onset rheumatoid arthritis

OBJECTIVE

To evaluate the prognostic value of rheumatoid factor (RF), detected in the Waaler-Rose agglutination assay and by nephelometry, in patients with recent-onset rheumatoid arthritis (RA).

METHODS

Consecutive patients with new-onset RA between 1993 and 1997 were followed for a median period of 4.7 years. Clinical data at baseline and drug use during the disease course were recorded. Outcome parameters studied were disease process, damage (erosions, joint surgery, extra-articular manifestations, and new co-morbidity), and death. Cut-off levels for RF were >40 IU/mL (nephelometry) and titres 1:160 (Waaler-Rose haemagglutination).

RESULTS

RF tests were negative by both methods in 22% of RA patients (RF- group), while 33% were RF positive by nephelometry only (RF+ group) and 45% were positive by Waaler-Rose and nephelometry (RF++ group). Baseline clinical and laboratory findings as well as the number of subsequently used disease-modifying anti-rheumatic drugs (DMARDs), the number of patients starting and the time spent on steroid therapy were similar in the three RF groups. Odd ratios for death (n = 23), erosions (n = 62), and serious extra-articular disease manifestations (EAMs) (n = 13) as well as patient survival, erosion-free or surgery-free survival rates did not differ between the RF groups. Only rheumatoid nodules were more frequent in RF++ patients.

CONCLUSION

The baseline presence of RF by either Waaler-Rose or nephelometry was not associated with differences in drug therapy, morbidity other than rheumatoid nodules, or mortality in RA patients in the first 5 years of disease. Being immunoglobulin M (IgM) RF positive thus had little impact on RA patient outcome.

Autoimmune disease etiology—a perplexing paradox or a turning leaf?

Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, or scleroderma have been considered to represent disorders associated with reaction of the patient's own immune system against self-antigens or body systems. In many such disorders, tissues involved show lesions or morphology indicating destructive inflammatory or reactive features clearly produced by or associated with cell-mediated or antibody-driven reactions of the patient against his own tissues. After an exhaustive search which has stretched back in time for at least the last five decades, we seem to understand how the immune system works better than previously. However, despite the fact that we now understand molecular mechanisms of antibody selection and structure, how the cell-mediated and humoral antibody system is activated in terms of signal peptides and in the context of HLA molecules, we have not yet exactly identified inciting antigens which clearly cause these diseases. The focus recently has shifted towards being able to down-modulate potentially harmful parts of a self-directed inflammatory process by abrogating harmful messenger molecules participating in tissue injury. Following such a path, we may actually alleviate or cure these diseases before eventually identifying their original cause.

Rheumatoid arthritis: proposal for the use of anti-microbial therapy in early cases

Rheumatoid arthritis (RA) is a chronic disease, affecting women more than men, especially in those possessing the "shared epitope" (EQK/RRAA) amino acid sequences present in HLA-DR1/4 molecules. Proteus mirabilis carries sequences showing molecular mimicry to the "shared epitope" and to type XI collagen of hyaline cartilage. Elevated levels of antibodies to P. mirabilis have been reported from 14 different countries involving 1375 RA patients and the microbe has been isolated from urine cultures of such patients. Our working hypothesis is that the disease develops as a result of repeated episodes of Proteus upper urinary tract infections. Prospective studies involving the trial of anti-Proteus measures in RA patients should be evaluated in the management of this disease. Antibiotics, high fluid intake, and fruit extracts, such as cranberry juice, have all been found to be effective in the treatment of urinary tract infections. Such measures could be used as possible additional adjuncts to the standard therapy with NSAIDs and DMARDs.

Complement activation in infective endocarditis: correlation with extracardiac manifestations and prognosis

In an infectious process complement activation is necessary for a proper immune and inflammatory response, but when exacerbated may cause tissue injuries. In infective endocarditis (IE) patients tend to develop high titres of circulating immune complexes (CIC) that activate complement. The aim of this study was to evaluate for the first time complement activation in IE for possible correlation with extracardiac manifestations and clinical prognosis. Twenty patients with IE, 14 healthy controls and 15 patients presenting mitral and aortic valve lesions (with no signs of either infection or other associated diseases), were studied. Plasma levels of C3adesArg, SC5b-9, C1rs-C1Inh and C3b(Bb)P were determined by ELISA and C3d by double decker immunoelectrophoresis. C3 and C4 levels were assayed by turbidimetry and CIC by ELISA. Elevation of plasma levels of all complement activation products, with the exception of C3b(Bb)P, indicated a significant classical pathway activation in IE patients when compared to controls (C3d: P < 0.00004; C3adesArg: P < 0.03, SC5b-9: P < 0.01, C1rs-C1Inh: P < 0.00007). CIC levels were significantly increased (P < 0.005) and C3 reduced in IE patients (P < 0.05). Elevated C3d (P < 0.02) and C3adesArg (P < 0.03) levels were associated with pulmonary manifestations. In addition, C3d was significantly elevated in the patients who died when compared to those who had a good recovery (P < 0.02). Our data demonstrate the activation of the complement classical pathway, most probably mediated by CIC, in IE and suggests C3d and C3adesArg as possible markers for extracardiac lesion and severity of the disease.

Individual value of each of the Duke criteria for the diagnosis of infective endocarditis

OBJECTIVES: To assess the value of each of the Duke criteria for the diagnosis of infective endocarditis (IE). METHODS: Detailed review was done of charts of all cases discharged with the diagnosis of IE, and classification as 'definite', 'possible' and 'rejected' cases was made according to the Duke criteria. The diagnostic impact of each criterion was assessed by reclassifying each 'definite' case after subtraction of each individual criterion and by reclassifying each 'possible' and 'rejected' case after addition of each individual criterion. RESULTS: From 1983 to 1993, 179 cases were identified in the databases of two hospitals. When the Duke criteria were applied, 124 (6967%) were classed as 'definite', 43 (2466%) as 'possible' and 12 (763%) as 'rejected' cases. Of the 67 pathologically proven cases, 52 (78610%) were 'definite' cases when the criteria were applied before pathology. If the major microbiological criterion is subtracted, 53% (69%) of the 'definite' cases become 'possible' or 'rejected'. When the echocardiographic criterion is subtracted, 34% (68%) of the 'definite' cases become possible or rejected. Among minor criteria, fever and predisposition, contributing to the classification of respectively 31% (68%) and 27% (68%) of the 'definite' cases, were the most powerful. On the other hand, the minor microbiological criterion and immunologic phenomena were responsible for the classification of only 2% (62%) and 6% (64%) respectively, of the 'definite' cases. CONCLUSIONS: Depending on the criterion examined, 47-98% of the 'definite' cases of IE would remain 'definite' if this particular criterion were absent. The major microbiological criterion had the highest relative importance. In this retrospective study, in which only 32 (18%) patients had a transesophageal echocardiogram, the echocardiogram contributed to 15% (66%) of the 'definite' cases according to the major criterion and to 19% (66%) according to the minor criterion. This study illustrates that the degree of certainty of the diagnosis of IE often depends on the presence/absence of only one criterion.

Does smoking stimulate rheumatoid factor production in non-rheumatic individuals?

Smoking has been associated with increased incidence of rheumatoid arthritis (RA), joint damage and positive rheumatoid factor (RF). Here we report an analysis of the association between smoking and IgM, IgG and IgA RF in a cohort of non-rheumatic individuals participating in a prospective longitudinal study of the incidence and significance of elevated RF. From the initial cohort of nearly 14,000 randomly selected individuals aged 52-80 years, 109 RF-positive and 187 RF-negative non-rheumatic participants were recruited. All participants were tested for RF at least twice at an interval ranging from 4 to 13 years. Of the RF-negative participants 21.9% were active smokers compared to 34.1% of IgM RF-positive (p=0.035), 20.8% of IgG RF-positive (N.S.) and 34.4% of IgA RF-positive participants (p=0.047). Smoking was most prevalent (44.8%) amongst participants with elevation of both IgM and IgA RF (p=0.008), and smokers were also significantly more likely to have a persistent elevation of RF than non-smokers (p=0.024). These findings indicate that smoking may influence the immune system, leading to increased production of IgM and IgA RF.

The antigen-binding domain of a human IgG-anti-F(ab')2 autoantibody

Recent studies revealed an immunoregulatory role of natural IgG-anti-F(ab')2 antibodies in both healthy individuals and patients with certain diseases. The implication of anti-F(ab')2 antibodies in the pathogenesis of diseases prompted us to study the gene segment structure of their antigen-binding domains and their binding characteristics. cDNA was prepared from the lymphocytes of a patient with a high IgG-anti-F(ab')2 serum titer. Variable heavy and light gene segments were amplified by PCR and inserted into a phagemid surface expression vector. Single-chain antibodies displayed on the phage surface were screened for binding to F(ab')2 fragments. The subsequent analysis of 95 single clones demonstrated that they all bound specifically to F(ab')2. Sequence analyses of 12 clones showed that 11 were identical and 1 contained a silent point mutation in the heavy chain and three amino acid exchanges in the light chain. The heavy chains belonged to the V(H)3 and the light chains to the V(kappa)2 gene family. The 11 identical light-chain genes were completely homologous to a germ-line sequence (DPK-15). Binding assays showed that the single-chain antibodies bind to F(ab')2, but not to Fab, Fc, or intact IgG. This binding pattern was confirmed by surface plasmon resonance studies, which revealed a relatively high affinity (Ka = 2.8 x 10(7) M(-1)). The strong binding capacity was further demonstrated by competitive inhibition of the serum anti-IgG antibody's interaction with antigen. The present study defines for the first time to our knowledge the gene segment structure of the antigen-binding domain of two human IgG-anti-F(ab')2 autoantibody clones and describes the binding kinetics of the purified monomeric fragments.

PROPERTIES OF VARIOUS ANTI-GAMMA-GLOBULIN FACTORS IN HUMAN SERA

The serological and physicochemical properties of the following three forms of human anti-γ-globulin factors were compared: (a) rheumatoid factors; (b) Milgrom type anti-γ-globulin factors; and (c) factors directed against an antigen in human γG-globulin that is hidden in the intact molecule and revealed by enzymatic digestion at low pH. The property common to these factors is ability to interact with human γG-globulin; they are distinguishable because they react with different antigenic groups on this molecule. In all of five sera, the Milgrom type anti-γ-globulin factors were γM-globulins. They reacted with various human γG-globulin antibodies but failed to interact with γM-globulin type antibodies in agglutination and absorption experiments. When isolated from other anti-γ-globulin factors, they agglutinated red cells coated with intact anti-Rh antibodies, but failed to react with cells cells coated with pepsin-digested anti-Rh antibody. These observations indicate that the agglutinator reacts with the crystallizable, inert fragment of γG-globulin. Anti-γ-globulin activity directed against an antigen in human γG-globulin revealed by pepsin digestion was demonstrated in γG-, γA-, and γM-globulins. This anti-γ-globulin factor could be absorbed by antigen-antibody precipitates containing human antibody, which shows that the hidden antigen in human γG-globulin is revealed not only by enzymatic digestion at low pH, but also when γG-globulin is present as antibody in an antigen-antibody precipitate. Rheumatoid factors and Milgrom type anti-γ-globulin factors were also absorbed by antigen-antibody precipitates containing human antibody. The results indicate that the three distinct forms of antiγ-globulin factors may all be produced as a result of antigenic stimulation by autologous antigen-antibody complexes.

Increased responsiveness of rheumatoid factor-producing B cells in seronegative and seropositive rheumatoid arthritis

OBJECTIVE

To compare the frequencies and responsiveness of rheumatoid factor (RF)-producing B cells in the peripheral blood of patients with seronegative and seropositive rheumatoid arthritis (RA).

METHODS

Frequencies of IgM+, IgG+, and RF+ B cells were determined by limiting-dilution analysis of purified peripheral blood B cells from 6 patients with seropositive RA, 8 patients with seronegative RA, and 7 normal controls. B cell help was provided by cloned T helper cells, which were stimulated by either anti-CD3 or the bacterial superantigen staphylococcal enterotoxin D (SED). IgM and IgG antibodies and RF in culture supernatants were detected by enzyme-linked immunosorbent assay.

RESULTS

In the presence of anti-CD3-stimulated T helper cells, 2-10% of B cells from normal individuals secreted IgM and IgG antibodies. The frequency of RF+ B cells was low and ranged from 1:182 to 1:885 (RF+: IgM+) B cells. In patients with seropositive RA, the numbers of Ig-producing B cells were reduced by a factor of 2, while the fraction of RF+ B cell precursors was expanded by more than 50-fold (7-20% of IgM+ B cells; P = 0.004). Patients with seronegative RA had higher frequencies of RF-producing B cells (1.5-6% of IgM+ B cells) than normal individuals (P = 0.002), but not to the same extent as seropositive patients (P = 0.002). Stimulation of B cells using SED preferentially induced RF+ B cells in normal controls and in patients with seronegative and seropositive RA.

CONCLUSION

B cell precursors with the potential to secrete RF were detectable in high frequencies in normal individuals and in patients with seropositive and seronegative RA. In all donors, these B cells could be stimulated with the bacterial superantigen SED. In normal individuals, RF+ B cells remained nonresponsive to help provided by anti-CD3-activated T cells, but were responsive in RA patients. Seronegative and seropositive RA form a continuous spectrum of disease, with a higher number of RF-secreting B cells in the seropositive patients.

Autoimmune mechanisms involved in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) was one of the first systemic disorders to be considered an autoimmune disease. Two major aspects of RA suggest a fundamental immune-mediated derangement in the disease: (1) presence of often massive lymphocytic infiltrates and activated CD4(+) T cells within the inflamed hypertrophied synovium, and (2) production of large amounts of rheumatoid factor (RF) by B-cells and plasma cells in the involved synovium itself. The actual tissue damage to joints and extra-articular structures affected by the disease comes from the rheumatoid inflammatory pannus or granulomatous collections of cells called rheumatoid nodules. RF production has long been studied as a prime example of apparent autoantibody production in association with the basic underlying disease process. RA patients who belong to subtype HLA DR4, Dw4 (DR B1 or 0401, Dw14 (0404/0408), or Dw15 (0405/0410) are most likely to be seropositive for RF and to have severe progressive disease. RFs are felt to represent an autoantibody associated with RA, since they show principal specificity for structures on the C gamma 3 and C gamma 2 (Fc) domains of IgG. Recent work by our group has defined a number of solvent-exposed linear RF-reactive epitopes on C gamma 3 and C gamma 2 using a strategy of overlapping 7-mers of primary sequence. RFs also have been demonstrated to react with two different regions, SKDWSFY and LSQPKIVKWDR, on beta 2-microglobulin (beta 2m). Many of the RF-reactive sites on C gamma 2 and C gamma 3 as well as on beta 2m show common immunodominant valines, leucines, tryptophanes, arginines, lysines, and glutamines, thus comprising common reactive residues. In the future, this approach may provide more direct insight into the specificities of other autoantibodies.

VH3-21 B cells escape from a state of tolerance in rheumatoid arthritis and secrete rheumatoid factor

BACKGROUND

Rheumatoid factor (RF) is a characteristic but not pathognomic feature in patients with rheumatoid arthritis (RA). It is unknown whether the repertoire of immunoglobulin genes utilized by RF+ B cells of RA patients is unique and whether RF+ B cells in normal individuals are silenced or deleted.

MATERIALS AND METHODS

Clonal B cell populations were established from the peripheral blood of normal donors (127 B cell clones), RA patients (113 RF- and 60 RF+ B cell clones) and patients with primary Sjögren's syndrome (82 RF- and 47 RF+ B cell clones) by coculturing with anti-CD3-stimulated T helper cell clones. The cross-reactivity pattern of antibodies secreted by the B cell clones was determined by ELISA on a panel of antigens. The molecular structure of the IgM heavy chains was characterized by VH family-specific RT-PCR and sequencing. VH elements which correlated with RF specificity were identified. The responsiveness of B cells expressing these VH elements to T helper cell signals was compared in normal individuals and RA patients.

RESULTS

The majority of RF+ B cells were monospecific when specificity was tested on five antigens. RF+ B cells expressed a significantly different repertoire of VH gene segments than RF- B cells. In particular, the VH3 gene segment V3-21 was not detected in B cell clones from normals but was the most frequent VH element in RF+ B cell clones from RA patients. Most of the V3-21 sequences were in germline configuration. The correlation between RF specificity and V3-21 gene segment usage was maintained in patients with Sjögren's syndrome. V3-21 transcripts were present in peripheral blood B cells from normal individuals. VH3-21+ B cells from RA patients but not from normal donors were responsive to preactivated T helper cells. Stimulation with a bacterial superantigen could overcome the nonresponsiveness of V3-21+ B cells in normal donors and induce the secretion of RF.

CONCLUSIONS

RF production is correlated with the usage of the V3-21 gene segment in two distinct RF+ diseases. In patients with these diseases, V3-21+ B cells secrete antibodies with RF activity in response to activated T helper cells. V3-21+ B cells remain in a state of nonresponsiveness in normal individuals that can be broken by superantigen stimulation. The germline configuration of VH3-21+ RF+ immunoglobulins in RA patients suggests that the loss of tolerance is not an antigen-driven process.

Selective induction of IgM rheumatoid factors by CD14+ monocyte-lineage cells generated from bone marrow of patients with rheumatoid arthritis

OBJECTIVE

To determine the capacity of CD14+ monocyte-lineage cells induced from bone marrow of rheumatoid arthritis (RA) patients to stimulate the production of IgM rheumatoid factor (IgM-RF), in order to explore the functional abnormalities of CD14+ cells and gain insight into the mechanism of selective synthesis of IgM-RF in RA.

METHODS

CD14+ cells were induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of CD14- cells purified from bone marrow cells obtained from 6 RA patients and 6 osteoarthritis (OA) patients. The production of IgM and IgM-RF was induced by stimulating B cells from normal healthy individuals with immobilized anti-CD3-activated autologous CD4+ T cells. The effects of CD14+ cells on the proportion of IgM-RF to total IgM produced by the normal B cells were assessed.

RESULTS

CD14+ cells induced by GM-CSF stimulation of bone marrow CD14- cells from the 6 RA patients significantly enhanced the proportion of IgM-RF to total IgM produced by anti-CD3-activated CD4+ T cell-stimulated normal B cells (P < 0.05), whereas GM-CSF-induced CD14+ cells from the bone marrow of the 6 OA patients did not significantly affect IgM-RF production. CD14+ cells induced by GM-CSF obtained from different sites in the same RA patient on different occasions consistently enhanced the proportion of IgM-RF to IgM produced by B cells from different normal subjects.

CONCLUSION

These results indicate that abnormal CD14+ monocytes stimulate RF-producing B cells to be ready to be activated by the signals delivered through noncognate T-B interactions with anti-CD3-activated T helper cells. Moreover, the data suggest that the accelerated generation of such functionally abnormal CD14+ cells from bone marrow precursors might play an important role in the pathogenesis of RA.

Rheumatoid factor production in the joint

Mononuclear cells derived from bone marrow, synovium and peripheral blood of patients with rheumatoid arthritis (RA) were examined for their capacity to produce rheumatoid factor (RF) in order to investigate the origin of circulating RF. The results demonstrate that mononuclear cells derived from bone marrow are able to produce IgG-, IgA- and IgM-RF and that the amounts of RF produced by bone marrow cells are not significantly different from that by dissociated synovial cells. Since circulating immunoglobulins are mainly derived from the bone marrow this observation suggests that also RF circulating in RA patients mainly originates from the bone marrow.

Persistence of a rheumatoid factor (RF)-producing B cell clone with a somatically mutated Ig kappa chain in a patient with rheumatoid arthritis

The V kappa IV gene encoding the light chain of an IgA has been shown to have undergone 31 somatic mutations compared with the single existing V kappa IV germ-line gene. We now show the persistence of the rearranged and mutated DNA coding for this RF over a period of 5 years in the peripheral blood lymphocytes (PBL) of the patient with rheumatoid arthritis (RA). The sequence of the RF has been conserved to identity over this period. These results raise the possibility that the particular antigenic stimulus leading to RF production in this RA patient is active over a long period of time.

Human rheumatoid factors with restrictive specificity for rabbit immunoglobulin G: auto- and multi-reactivity, diverse VH gene segment usage and preferential usage of V lambda IIIb

To determine the molecular and functional properties of human rheumatoid factors (RF), we established stable hybridomas and Epstein-Barr virus-transformed B cell lines from the synovial fluid or peripheral blood of three patients with rheumatoid arthritis and one patient with systemic lupus erythematosus. 17 cell lines were obtained that produced high-titer immunoglobulin M (IgM) RF that reacted exclusively with rabbit but not human IgG or IgG of other mammalian species. Certain anti-rabbit IgG RF also had specificity for other mammalian antigens (Ag), including cytoskeletal proteins and intracellular proteins found in HeLa cells, as well as for Ag present in an extract prepared from the cell wall of group A streptococci. 13 of the 17 RF contained lambda-type light (L) chains, of which 12 were classified serologically as members of the lambda-L chain variable region (V lambda) subgroup, designated V lambda III. The heavy chain V region (VH) and V lambda sequences of nine of these IgM lambda RF were determined at the cDNA level. Five VH genes in three VH families were used by these antibodies (Ab), including VH1 (dp21/1-4b and dp10 [51p1]/hv1051), VH3 (dp38/3-15 and dp77/13-21), and VH4 (dp70/4-4b). The deduced V gene-encoded amino acid sequences of the lambda chains of these IgM lambda RF confirmed their serological classification as lambda III, and they were further classified as members of the relatively uncommon V lambda III subgroup, designated V lambda IIIb. Based on cDNA analyses, nine were the product of three different V lambda III b germline genes. Two such genes, designated hsiggll150 and hsiggll295, were cloned and sequenced from genomic DNA. Unique combinations of these VH and V lambda III b genes could be related to distinctive patterns of reactivity among the IgM lambda RF. Although the VH and V lambda regions of these Abs were expressed primarily as germline-encoded sequences, four of nine multireactive Abs had extensive V region mutation, indicative of an Ag-driven process. The finding that lambda IIIb L chains are preferentially found among anti-rabbit IgG RF, and that some of these Ab have specificity for other protein, cellular, and bacterial Ag, provides new insight into the pathogenesis of RA and related diseases.

New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service

PURPOSE

This study was designed to develop improved criteria for the diagnosis of infective endocarditis and to compare these criteria with currently accepted criteria in a large series of cases.

PATIENTS AND METHODS

A total of 405 consecutive cases of suspected infective endocarditis in 353 patients evaluated in a tertiary care hospital from 1985 to 1992 were analyzed using new diagnostic criteria for endocarditis. We defined two "major criteria" (typical blood culture and positive echocardiogram) and six "minor criteria" (predisposition, fever, vascular phenomena, immunologic phenomena, suggestive echocardiogram, and suggestive microbiologic findings). We also defined three diagnostic categories: (1) "definite" by pathologic or clinical criteria, (2) "possible," and (3) "rejected." Each suspected case of endocarditis was classified using both old and new criteria. Sixty-nine pathologically proven cases were reclassified after exclusion of the surgical or autopsy findings, enabling comparison of clinical diagnostic criteria in proven cases.

RESULTS

Fifty-five (80%) of the 69 pathologically confirmed cases were classified as clinically definite endocarditis. The older criteria classified only 35 (51%) of the 69 pathologically confirmed cases into the analogous probable category (p < 0.0001). Twelve (17%) pathologically confirmed cases were rejected by older clinical criteria, but none were rejected by the new criteria. Seventy-one (21%) of the remaining 336 cases that were not proven pathologically were probable by older criteria, whereas the new criteria almost doubled the number of definite cases, to 135 (40%, p < 0.01). Of the 150 cases rejected by older criteria, 11 were definite, 87 were possible, and 52 were rejected by the new criteria.

CONCLUSION

Application of the proposed new criteria increases the number of definite diagnoses. This should be useful for more accurate diagnosis and classification of patients with suspected endocarditis and provide better entry criteria for epidemiologic studies and clinical trials.

Rheumatoid factor production by mononuclear cells derived from different sites of patients with rheumatoid arthritis

To investigate the origin of circulating rheumatoid factor (RF) and the relation between RF production at different sites in patients with rheumatoid arthritis (RA), mononuclear cells derived from bone marrow, synovium and peripheral blood of patients with RA were examined for the presence of plasma cells and for their capacity to produce RF and other immunoglobulins in vitro. Analysis of culture supernatants for the presence of immunoglobulins demonstrated that cells derived from bone marrow, synovium and peripheral blood were all found to be capable of producing every immunoglobulin and RF isotype investigated. No significant correlations were found between concentrations of immunoglobulin isotypes produced by cells derived from different sites of one individual. Significant correlations were found, however, between concentrations of RF isotypes produced by cells derived from the three sites. These results indicate that the production of RF in the different compartments is not an autonomously regulated process. Mononuclear cells derived from bone marrow were found to be able to produce RF in similar quantities to cells dissociated from synovial tissue. In combination with the fact that circulating immunoglobulins are produced mainly in the bone marrow, this observation suggests that bone marrow is also a major source of circulating RF.

IL-2 enhances polyclonal IgM but not IgM-rheumatoid factor synthesis by activated human peripheral blood B cells

IgM-rheumatoid factor (RF) is thought to be involved in the pathogenesis of rheumatoid arthritis (RA). Several cytokines are known to regulate immunoglobulin synthesis. In this study the effects of IL-2 on polyclonal IgM and IgM RF synthesis were compared. Cytokines were added to peripheral blood B cells from normal subjects and patients with RA after activation by Staphylococcus aureus Cowan 1 (SAC). The addition of IL-2, but not IL-4 or IL-6, resulted in significant enhancement of IgM synthesis in cultures from both healthy subjects and patients with RA. Similar degrees of enhancement were seen in both peripheral blood mononuclear cell and highly purified B cell cultures. IgM-RF was synthesized after activation in cultures from healthy subjects and spontaneously in cultures from RA patients. In contrast to polyclonal IgM synthesis, IL-2 failed to augment IgM-RF synthesis in cell cultures from either healthy subjects or RA patients. This study demonstrates different effects of IL-2 on IgM and IgM-RF synthesis.

The repertoire of rheumatoid factor-producing B cells in normal subjects and patients with rheumatoid arthritis

OBJECTIVE

To compare the B cell repertoire of normal individuals and patients with rheumatoid arthritis (RA) and, specifically, to identify precursor B cells with the potential to secrete rheumatoid factor (RF) and to understand the T helper cell requirements for the production of this autoantibody.

METHODS

Frequencies of precursors of IgM-, IgG-, and RF-producing B cells were measured in a limiting-dilution system. Two distinct sources of T cell help were compared. T cell help was provided by anti-CD3-activated CD4+ human T cell clones, or T cell-B cell interaction was facilitated by the bacterial super-antigen staphylococcal enterotoxin D (SED).

RESULTS

A subset of 2-14% of peripheral blood B cells secreted IgM and IgG in SED-driven cultures. The SED-responsive B cell subpopulation was present at 10 times higher frequency in normal donors compared with RA patients. However, the repertoires were very similar, particularly for RF+ precursors, which represented approximately one-third of all SED-responsive B cells. In normal individuals, most of these RF+ precursor B cells did not respond to anti-CD3-activated T helper cells, with only a very small fraction of B cells activated by anti-CD3-driven helper cells maturing into RF-secreting B cells (from 1 of 182 to 1 of 889 IgM-producing B cells). This subset was expanded approximately 50-fold in RA patients.

CONCLUSION

Normal subjects and RA patients share a pool of B cells which secrete RF when activated in the presence of SED and T helper cells. These B cells are frequent and obviously anergic in normal individuals. The B cell subset with the potential to produce RF when help is provided in noncognate T-B interaction (anti-CD3-driven T cells) is considerably expanded in RA patients, probably reflecting an increased responsiveness of such B cells to helper signals.

Rheumatoid factors from patients with rheumatoid arthritis react with tryptophan 60 and 95, lysine 58, and arginine 97, on human beta 2-microglobulin

OBJECTIVE

To define precise epitopes on human beta 2-microglobulin (beta 2m) reacting with polyclonal IgM rheumatoid factors (RF) from patients with rheumatoid arthritis (RA).

METHODS

Ten polyclonal RF were tested for their human beta 2m epitope-binding specificities using the entire 99-amino acid sequence synthesized as overlapping 7-mers in an enzyme-linked immunosorbent assay. Glycine substitution for each residue within RF-reacting linear regions was employed to define major reactive sites.

RESULTS AND CONCLUSION

Major beta 2m residues contributing to RF reactivity were tryptophans at positions 60 and 95, lysine at 58, and arginine at position 97.

Spontaneous in vitro production of rheumatoid factor during infectious exacerbations of cystic fibrosis: correlation with circulating immune complex levels

Rheumatoid factor (RF) production has been demonstrated during infections, including infectious exacerbations of cystic fibrosis (CF). The aim of this study was to evaluate the relationship of RF production to infection, and examine the mechanisms involved. Serial peripheral blood mononuclear cell (PBMC) cultures with measurement of spontaneous production of IgM RF, IgA RF, total IgM and IgA, and measurement of serum levels of immune complexes were carried out during exacerbations of CF. The percentage of B cells expressing CD5 was examined in a second cohort of acutely infected CF patients, and related to IgM RF production. IgM RF production was significantly elevated during acute infection compared with convalescence (P < 0.05), stable CF subjects (P < 0.005) and normal controls (P < 0.05). IgM RF production did not correlate with total IgM production in the majority of patients, but was closely related to circulating immune complex levels in 8/10 subjects. IgA RF production did not increase significantly during infection, and did not correlate with total IgA or IgM RF production, or with circulating immune complex levels. CD5+ B cells were not increased in the CF group, and the percentage of CD5+ B cells did not correlate with IgM RF synthesis. These observations suggest that RF production during infection is specifically induced, possibly by immune complex autoimmunization, and is not simply the result of polyclonal B cell activation. Different patterns of IgM RF and IgA RF synthesis suggest different mechanisms of induction.

Nucleotide sequence analysis of rheumatoid factors and polyreactive antibodies derived from patients with rheumatoid arthritis reveals diverse use of VH and VL gene segments and extensive variability in CDR-3

The heavy and light chain nucleotide sequences of 17 monoreactive and polyreactive rheumatoid factors largely derived from the inflamed synovial tissue of two patients with rheumatoid arthritis are described. Some of these sequences have been the subject of a previous report from our laboratories. Additionally, a few rheumatoid factors from the peripheral blood of patients with systemic lupus erythematosus and Sjogren's syndrome as well as a normal individual are included. A review of our previous results as well as the new data provided within this paper lead to the following major conclusions: (1) Rheumatoid factors and polyreactive antibodies derive from a diverse array of VH and VL gene segments; (2) While many rheumatoid factors and polyreactive antibodies are direct or nearly direct copies of germline genes, some show clear evidence of somatic mutation; (3) The CDR3 of all of these antibodies is extraordinarily diverse in length and composition. Certain 'restrictions' do appear in this very large sample: (a) the polyreactive antibodies are exclusively lambda, and (b) there seems to be a preponderance of a particular subset of VH3 genes beyond that one would expect based on random utilization.

Selective induction of rheumatoid factors by superantigens and human helper T cells

Production of autoantibodies specific for the Fc region of autologous IgG, called rheumatoid factors (RF), is a characteristic finding in patients with rheumatoid arthritis (RA). To study the requirements regulating the synthesis of these autoantibodies, we have cloned human helper T cells and co-cultured them with purified B cells. To mimic cognate T-B cell interaction, we have used bacterial superantigens that function by cross-linking HLA molecules on the B cell with selected T cell receptor (TCR) molecules expressing a particular polymorphism of the V beta gene segment. Data presented here demonstrate that the staphylococcal enterotoxin D (SE D), but not other bacterial superantigens, exhibits an ability to induce IgM, IgG, and especially RF production, in B cells from RA patients and normal individuals. Comparison with the polyclonal antibody production in B cell cultures driven by anti-CD3-stimulated T cell clones confirmed that SE D shifted the repertoire of secreted antibodies toward immunoglobulins with Fc binding specificity, suggesting that SE D preferentially stimulates RF+ B lymphocytes. B cells with the potential to secrete RF were highly frequent in RA patients, requiring as few as 150 peripheral B cells/culture to detect RF in the culture supernatants. SE D-induced RF synthesis was strictly dependent on the presence of selected CD4+T helper cells and required a direct membrane contact between B cells and T helper cells. Here, we propose a model that SE D selectively induces RF production depending on the availability of SE D responsive T cells in the TCR repertoire of the responder.

Complete sequence of the genes encoding the VH and VL regions of low- and high-affinity monoclonal IgM and IgA1 rheumatoid factors produced by CD5+ B cells from a rheumatoid arthritis patient

We have characterized the VH and VL genes of three low-affinity polyreactive and two high-affinity monoreactive IgM and IgA1 rheumatoid factor (RF) mAb generated using circulating CD5+ B cells from a single rheumatoid arthritis patient. We found that four and one RF mAb utilized genes of the VHIV and VHIII families, respectively. The VHIV gene usage by these RF mAb differs from the preferential VHIII, VHI, and, to a lesser extent, VHII gene usage by the IgM with RF activity found in patients with mixed cryoglobulinemia, Waldenstrom's macroglobulinemia, and other monoclonal gammopathies. In addition, in contrast to the preponderant kappa L chain usage by the RF in these patients, a lambda L chain was utilized by all RF mAb from our rheumatoid arthritis patient. Two RF mAbs utilized V lambda I, two V lambda IV, and one V lambda III L chains. The VH genes of the two low-affinity polyreactive IgM RF mAb were in germline configuration. When compared with the deduced amino acid sequence of the putatively corresponding genomic segment, the VH gene of the high-affinity monoreactive IgM RF mAb displayed five amino acid differences, all of which are in the complementarity determining regions (CDR), possibly the result of a process of somatic point mutation and clonal selection driven by Ag. The unavailability of the corresponding genomic VH segment sequences made it impossible to infer whether the VH genes utilized by the two IgA1 RF were in a germline or somatically mutated configuration. Sequencing of the genes encoding the H chain CDR3 (D segments) revealed that all three low-affinity polyreactive RF mAb displayed a much longer D segment (36-45 bases) than their high-affinity monoreactive counterparts (15-24 bases), raising the possibility that a long D segment may be one of the factors involved in antibody polyreactivity.