Detection of antibodies to small nuclear ribonucleoproteins and small cytoplasmic ribonucleoproteins using unlabeled cell extracts

RNA molecules immunoprecipitated with sera from patients who have rheumatic diseases can be readily detected in polyacrylamide gels by using ethidium bromide and silver stains. With these stains, we found that RNA patterns characteristic of a broad range of specific small nuclear ribonucleoproteins and small cytoplasmic ribonucleoproteins were recognizable. The stains correctly identified antibodies to ribonucleoproteins in 33 (92%) of 36 patient sera selected for study because of known antibody specificities. The silver stain method detected antibodies to ribonucleoproteins in 25 (76%) of 33 patients with classic systemic lupus erythematosus, a frequency that approximated the frequency observed in the Lerner-Steitz assay, which is based on autoradiography. This approach considerably simplifies the latter radioimmunoassay with minimal loss of precision and sensitivity.

The major core histone antigenic determinants in systemic lupus erythematosus are in the trypsin-sensitive regions

Antibody responses against nucleosome core histones in systemic lupus erythematosus have been shown, by immunoblotting, to be directed largely against the trypsin-sensitive regions of the histones. These occur at the N-terminal regions of all 4 core histones and at the C-terminal ends of H2A and H3. Since these regions are often not the most antigenic when individual histones are used as immunogens, and appear to be exposed in the nucleosome, the active immunogens in systemic lupus erythematosus seem likely to be chromatin-bound, rather than free, histones.

Lyme disease: a unique human model for an infectious etiology of rheumatic disease

Lyme disease is a complex immune-mediated multi-system disorder that is infectious in origin and inflammatory or "rheumatic" in expression. Through its epidemiologic characteristics, large numbers of a seasonally synchronized patient population are readily available for prospective study. Lyme disease has a known clinical onset ("zero time"), marked by the characteristic expanding skin lesion, erythema chronicum migrans, and a clearly defined pre-articular phase. At least some manifestations of the disorder are responsive to antibiotics, and the causative agent--a spirochete--is now known. These advantages make Lyme disease unique as a human model for an infectious etiology of rheumatic disease.

The pathogenesis of arthritis in Lyme disease: humoral immune responses and the role of intra-articular immune complexes

We studied 78 patients with Lyme disease to determine how immune complexes and autoantibodies are related to the development of chronic Lyme arthritis. Circulating C1q binding material was found in nearly all patients at onset of erythema chronicum migrans, the skin lesion that marks the onset of infection with the causative spirochete. In patients with only subsequent arthritis this material tended to localize to joints where it gradually increased in concentrations with greater duration of joint inflammation. In joints, its concentration correlated positively with the number of synovial fluid polymorphonuclear leukocytes. Despite the prolonged presence of putative immune complexes, rheumatoid factors could not be demonstrated. These observations suggest that phlogistic immune complexes based on spirochete antigens form locally within joints during chronic Lyme arthritis.

Antibodies to histones in systemic lupus erythematosus: localization of prominent autoantigens on histones H1 and H2B

By the technique of immunoblotting we have assessed the ability of sera from 24 patients with systemic lupus erythematosus to bind nuclear proteins. Of the 11 patients who had antibodies to histones, 10 had antibodies to histone H1 and 9 of these also had antibodies to histone H2B. Antibodies to the other histones (H2A, H3, and H4) were less apparent. Five of the 11 patients (and two others in the remainder of the sample of 24) also had antibodies to a small number of nonhistone proteins that are probably components of ribonucleoprotein particles, but there was no obvious correlation between the presence of antihistone antibodies and the known antiribonucleoprotein activity of these sera. Separate determinants on H1 and H2B were demonstrated by immunoblotting with affinity-purified anti-H1 and anti-H2B antibodies derived from serum that showed both specificities. The localization of the determinants within the histone polypeptide chains was shown by immunoblotting with large fragments produced by specific proteolytic or chemical cleavage of the histones. The strongest determinant on H1 was located within the COOH-terminal half, with a weaker determinant being present within the NH2-terminal half; the H2B determinant(s) was located entirely within the NH2-terminal half of the molecule. The selectivity with which the antihistone antibodies in systemic lupus erythematosus are produced against the more exposed histones in the nucleosome (and perhaps against the most exposed regions of these histones) is consistent with the involvement of intact chromatin structures as immunogens in this disease.

Saturable, high-avidity monocyte receptors for monomeric IgG and Fc fragments increase in SLE and lyme disease

We have devised an assay for quantifying high-avidity Fc receptors for monomeric IgG on peripheral blood monocytes. In the development of a radiolabelled ligand for the assay, we found that Fc fragments offer several advantages over 7S-IgG. Compared to the latter ligand, the fragments interacted more cleanly with a single high-avidity binding site, appeared to have easier access to this site, and, since they showed no binding to Millipore filters, their use made possible a wash procedure that was convenient and rapid, thus minimizing loss of specifically bound ligand. Application of the assay to a study of ten normal controls, five patients with SLE, and three patients with Lyme disease demonstrated that normal monocytes bear approximately 10,000 high-avidity binding sites per cell. In contrast, patient monocytes bore significantly more Fc receptors; on average their cells had about 40,000 such sites per cell (P = 0.01) and sometimes as many as 100,000 sites per cell. Both normal and patient monocytes bound IgG or Fc fragments with an apparent association constant (KA) of approximately 10(8) M-1. The majority of patients with active SLE and Lyme disease had serum C1q-binding material compatible with the presence of circulating immune complexes. This study shows that these putative circulating immune complexes do not necessarily lead to a reduction in the number of Fc receptors on peripheral blood monocytes. Rather, the data suggest that in the course of immune mediated diseases, either monocytes are activated in vivo to express greater numbers of Fc receptors, or a subset of monocytes bearing more Fc receptors is expanded.

Evidence for Pseudomonas antigen in immune complexes in Pseudomonas osteomyelitis

In infections associated with immune complex disease, microbial antigens have rarely been found in the complexes. Using an enzyme-linked immunoassay, we studied the immune complexes of a patient who had hematogenous Pseudomonas aeruginosa osteomyelitis associated with palpable purpura, arthritis, and microscopic hematuria. After separation of the complexes into high and low molecular weight fractions, a 6-fold selective concentration of P aeruginosa antibody was found in the low molecular weight fraction compared with the concentration of the serum. Following disruption of immunoglobulin, the high molecular weight fraction competed with solid-phase P aeruginosa antigen for P aeruginosa antibody from another source. After successful treatment of the infection, the patient's symptoms resolved, and the complexes disappeared. These findings strongly suggest that immune complexes in this patient contained P aeruginosa antigen and antibody that may have been pathogenetic in his disease.

Antibodies from patients with connective tissue diseases bind specific subsets of cellular RNA-protein particles

We characterized the RNA-containing antigens precipitated by sera from 260 patients with positive antinuclear antibodies. 49 individuals, most of whom had systemic lupus erythematosus or Sjögren's syndrome, possessed antibodies that precipitated the previously identified RNP, Sm, Ro, and La antigens either singly or in combinations. These antigens, which are located on discrete sets of small nuclear or cytoplasmic RNA-protein particles, exhibited a number of antigenic interrelationships. One patient's serum recognized a new particle containing a small RNA which we have called Th; it also precipitated the Ro complexes. Other patients with systemic lupus erythematosus, hepatitis B virus infection, juvenile rheumatoid arthritis, myositis, and rheumatoid arthritis had antibodies that precipitated specific subsets of ribosomal RNA and transfer RNA. One patient's serum contained a monoclonal immunoglobulin G that precipitated ribosomes. Most of these antibodies identified antigenic determinants constituted at least in part of protein. The specificity of the proteins bound to particular cellular RNA, probably explains the exquisite precision with which antibodies from rheumatic disease patients discriminate among RNA subsets. Such sera should be useful probes for investigating specific roles that different RNA and RNA-protein complexes play in cellular metabolism.

Cryoprecipitogogue from normal serum: mechanism for cryoprecipitation of immune complexes

We designed this study to examine the relationship of cryoglobulins to immune complexes in sera of patients with rheumatic or infectious diseases. Polyethylene glycol was used to precipitate large proteins from normal serum and then was dialyzed away. The precipitated proteins were soluble in warm phosphate-buffered saline but at 4 degrees C they reversibly reprecipitated. As they reprecipitated, they selectively coprecipitated cold-soluble immune complexes. By NaDodSO4/polyacrylamide gel electrophoresis, these normal, nonimmunoglobulin cryoproteins were similar to the nonimmunoglobulin constituents of washed cryoimmunoglobulins from patients with rheumatic or infectious diseases. These findings suggest that cryoprecipitability is a property not of immune complexes themselves but of a group of large normal serum proteins. In inflammatory diseases, the concentrations of some of these proteins, responding as acute-phase reactants, may increase to the point where intermolecular attractive forces become prominent, particularly in the cold. Cold-augmented molecular aggregation between these nonimmunoglobulin proteins and immune complexes could then act to decrease their collective solubility and result in the cryoprecipitation of otherwise cold-soluble immune complexes.

Two novel classes of small ribonucleoproteins detected by antibodies associated with lupus erythematosus

The RNP and Sm antigens recognized by lupus erythematosus antibodies are located on discrete particles containing single small nuclear RNA's complexed with proteins. The antigens Ro and La are also on ribonucleoproteins. The small RNA's in ribonucleoproteins with Ro are discrete, like those associated with RNP and Sm; in contrast, ribonucleoproteins with La contain a striking highly banded spectrum of small RNA's from uninfected cells as well as virus-associated RNA from adenovirus-infected cells.

Isolation of human monocytes on re-orienting gradients of Percoll

We have developed a rapid and simple method for isolating monocytes from peripheral blood. After mononuclear cells are isolated on a Ficoll-Hypaque gradient, the monocytes are purified by sedimentation for 5 min through a re-orienting gradient of Percoll. The method is easily reproducible and yields approximately half of the monocytes in staring blood, with minimal contamination by lymphocytes. Although both monocytes and lymphocytes have similar densities, separation occurs because these cells migrate at differing rates through the gradient to reach their equilibration point. The recovered monocytes are viable and functional; over 95% of them exclude trypan blue and they adhere to glass and plastic and ingest latex particles normally. By virtue of the rapidity and gentle nature of its centrifugation steps, the method exposes cells to only very limited non-physiologic conditions. For this reason and because the monocytes are maintained in suspension, opportunities for functional alterations are minimized.

Immune complexes and the evolution of Lyme arthritis. Dissemination and localization of abnormal C1q binding activity

In a prospective study of 78 patients with Lyme arthritis, abnormal serum C1q binding activity was present at the initial onset of erythema chronicum migrans in nearly all cases. The abnormal binding persisted in patients with subsequent nerve or heart involvement. In contrast, among those with only subsequent arthritis, it usually disappeared within three months (P = 0.018). However, in the synovial fluid of affected joints, abnormal binding was uniformly present, and always to a greater extent than in the circulation. The abnormally reactive material behaved like antigen-antibody complexes. It had a density of 19S or greater, dissociated below pH 4.2, and lacked antiglobulin activity. Cryoprecipitates containing immunoglobulin were good but insensitive predictors of its presence, but immune complexes themselves did not seem primarily responsible for cryoprecipitability. Thus, as judged by C1q binding, immune complexes remain disseminated in certain patients with Lyme arthritis but localize to joints in others.

Chronic Lyme arthritis. Clinical and immunogenetic differentiation from rheumatoid arthritis

Ten patients with Lyme arthritis have developed chronic involvement of one or both knees. Lyme arthritis was diagnosed by onset with erythema chronicum migrans (six patients); residence in Lyme, Connecticut (eight); seasonal onset in summer and early fall (nine); early periods of short recurrent attacks (nine); absence of rheumatoid factor (nine); and absence of symmetrical polyarthritis, morning stiffness, subcutaneous nodules, or antinuclear antibodies (in all). Five patients had synovectomies; pannus formation and underlying cartilage erosion were present in all. Seven of the 10 patients had the same B-cell alloantigen, DRw2 (frequency in normal control subjects, 22% [P less than 0.005]), but did not have an increased frequency of the alloantigens associated with rheumatoid arthritis. Chronic Lyme arthritis, the result of an apparent tick-transmitted infection, resembles rheumatoid arthritis pathologically but generally differs from it in both prearticular and immunogenetic characteristics.

Lyme arthritis: correlation of serum and cryoglobulin IgM with activity, and serum IgG with remission

Forty-eight patients with erythema chronicum migrans (ECM) were studied prospectively for 6 to 18 months. Twenty-six patients had no later symptoms, but 22 subsequently developed Lyme arthritis and 9 of them also experienced neurologic abnormalities. Eighty-seven percent of patients with active ECM followed by subsequent involvement had cryoglobulins containing IgM compared to only 13% of those with active ECM and no later symptoms. The former group also had significantly lower IgG, C3 and C4 levels. Sixty-seven percent of patients still had serum cryoglobulins when neurologic disease was most active, and 45% had them when joint symptoms were most severe, but only 11% continued to have small amounts in remission. The number of patients who continued to have serum cryoglobulins with recurrent attacks of arthritis decreased with time. In contrast, patients always had cryoglobulins in joint fluid, a finding Lyme arthritis shares with rheumatoid arthritis. The cryoprecipitates from 2 of 10 patients contained particles with internal structure, but their viral nature is problematic. All components of antisera obtained from goats and rabbits immunized with cryoglobulins were absorbed by normal human sera. The amount of IgM in cryoglobulins correlated directly with serum IgM, which generally rose during exacerbations and fell during remissions; serum IgG and IgA moved conversely. Thus, IgM was an important correlate of clinical disease activity and IgG or remission.

Circulating immune complexes in Lyme arthritis. Detection by the 125I-C1q binding, C1q solid phase, and Raji cell assays

We have found immunoglobulin (Ig) G-containing material consistent with immune complexes in the sera of patients with Lyme arthritis. It was detected in 29 of 55 sera (55%) from 31 patients by at least one of three assays: (125)I-C1q binding, C1q solid phase, or Raji cell. The presence of reactive material correlated with clinical aspects of disease activity; it was found early in the illness, was most prominent in sera from the sickest patients, was infrequent during remissions, and often fluctuated in parallel with changes in clinical status. The results in the two C1q assays showed a strong positive correlation (P<0.001). They were each elevated in 45% of the sera and were usually concordant (85%). In contrast, the Raji cell assay was less frequently positive and often discordant with the C1q assays. In sucrose density gradients, putative circulating immune complexes sedimented near 19S; they, too, were detected best by the two assays based on C1q binding. An additional 7S component was found in some sera by the (125)I-C1q binding assay. Serum complement was often above the range of normal in patients with mild disease and normal in patients with severe disease but did not correlate significantly with levels of circulating immune complexes. IgM and IgG rheumatoid factors were not detectable. These findings support a role for immune complexes in the pathogenesis of Lyme arthritis. Their measurement, by either the (125)I-C1q binding assay or by the C1q solid phase assay, often provides a sensitive index of disease activity. Moreover, the complexes are likely sources of disease-related antigens for further study of this new disorder.

IgM receptors on human lymphocytes: detection by direct binding

Radioiodinated IgM isolated from a patient with Waldenström macroglobulinemia binds with high avidity (apparent Ka = 2.5 x 10(9) M-1) to freshly isolated human peripheral blood lymphocytes. Binding occurred through the Fc region of the molecule and involved a receptor specific for immunoglobulins of the IgM class. The avidity and specificity of this binding are consistent with a biologic role for IgM receptors on lymphocytes.

Lyme arthritis: a new clinical entity

Named for the Connecticut town where the first identified cases occurred in 1972, this disorder has since been found elsewhere and may be caused by a virus transmitted by ticks. Attacks are often preceded by erythema chronicum migrans and are seldom prolonged, though they may recur. Symptomatic treatment only is advised, except in the rare instances of severe neurologic complications or myocardial conduction abnormality.

Erythema chronicum migrans and Lyme arthritis: cryoimmunoglobulins and clinical activity of skin and joints

We report the presence of serum cryoimmunoglobulins in patients with attacks of a newly described epidemic arthritis--Lyme arthritis--and in some patients with a characteristic skin lesion--erythema chronicum migrans--that sometimes precedes the onset of the arthritis. Seven patients who had cryoimmunoglobulins at the time of the skin lesion have developed arthritis; four patients without them have not. The cryoglobulins in patients with the skin lesion consisted primarily of immunoglobulin M (IgM); those in patients with arthritis often included both IgM and IgG. These findings support the hypothesis that a common origin exists for the skin and joint lesions and suggest that circulating immune complexes may have a pathogenetic role in Lyme arthritis.

Erythema chronicum migrans and Lyme arthritis. The enlarging clinical spectrum

Thirty-two patients with the onset of erythema chronicum migrans, Lyme arthritis, or both in mid-1976 were studied prospectively. The skin lesion (24 patients) typically lasted about 3 weeks, beginning as a red macule or papule that expanded to form a large ring with central clearing. Associated symptoms ranged from none to malaise, fatigue, chills and fever, headache, stiff neck, backache, myalgias, nausea, vomiting, and sore throat. Three patients had been bitten by ticks at the site of the initial lesion 4 to 20 days before its onset. Nineteen patients suddenly developed a monoarticular or oligoarticular arthritis 4 days to 22 weeks (median, 4 weeks) after onset of the skin lesion; eight developed arthritis without a preceding skin lesion. Seven of these 27 experienced migratory joint pains. Arthritis attacks, most commonly in the knee, were typically short (median, 8 days) but sometimes persisted for months. Other manifestations included neurologic abnormalties, myocardial conduction abnormalities, serum cryoprecipitates, elevated serum IgM levels, and elevated erythrocyte sedimentation rates. The diagnostic marker is the skin lesion; without it, geographic clustering is the most important clue.

Tissue factor generation by human mononuclear cells: effects of endotoxin and dissociation of tissue factor generation from mitogenic response

The effects of the presence of endotoxin in a mononuclear cell culture system have been assessed. Endotoxin was shown to be mitogenic for human peripheral blood lymphocytes and capable of stimulating the generation of tissue factor. Concentrations of endotoxin, found to contaminate many commercial mitogens and antigens, activated mononuclear cells in a time-dependent manner. Generation of tissue factor was detected in cultures harvested from 2 to 72 hours following stimulation with endotoxin. Dose-response curves relating concentrations of endotoxin to mononuclear cell stimulation were determined; as little as 0.001 microng/ml. of E. coli endotoxin was capable of stimulating the generation of tissue factor in the cell cultures. The mitogenic effect of endotoxin was modest, however, and appeared to be unrelated to the ability of endotoxin to active tissue factor. Inhibition of DNA synthesis in the cell cultures by cytosine arabinoside or nonlethal irradiation failed to impair the generation of tissue factor. Endotoxin contamination of various reagents used in cell culture was evaluated with the Limulus assay, which detected as little as 1 X 10(-4) microng/ml. of endotoxin. Endotoxin was detected in preparations of phytohemagglutinin, purified protein derivative of the tubercle bacillus, mumps vaccine, tetanus toxoid, concanavalin A, and pokeweed mitogen. Because of the broad implications of contamination by endotoxin of various reagents, we assessed the specificity of the Limulus assay for the detection of endotoxin in the lectin, concanavalin A, and determined that the reaction was specific for endotoxin. Contamination by endotoxin of mononuclear cell culture systems should be considered as a possible factor in the production of various biological effects attributed to some commonly used mitogens and antigens.

Spontaneous peritonitis and systemic lupus erythematosus. Importance of accurate diagnosis of gram-positive bacterial infections

Primary Gram-positive bacterial peritonitis developed in three patients with systemic lupus erythematosus (SLE). These cases suggest a possible association between these two entities. Furthermore, they emphasize the importance of accurate diagnosis when evaluating abdominal symptoms in patients with SLE.