Reactivity of anti-histone antibodies induced by procainamide and hydralazine

Multiple intra-articular injections with adipose-derived stem cells for knee osteoarthritis cause severe arthritis with anti-histone H2B antibody production

Introduction

Osteoarthritis (OA) is the most common form of arthritis. OA results from the breakdown of cartilage, which leads to deterioration of the entire joint and the connective tissue that holds the joint together, and gradually and irreversibly worsens over time. Adipose-derived stem/stromal cells (ADSCs) have been used in the treatment of knee OA. However, the safety and efficacy of ADSC treatment of OA remain unclear. In this study, we investigated the pathophysiology of severe knee arthritis that occurred after ADSC treatment by screening for autoantibodies in synovial fluid from patients who received ADSC treatment.

Methods

Adult Japanese patients with OA who received ADSC treatment at Saitama Cooperative Hospital between June 2018 and October 2021 were enrolled. Antibodies (Abs) were screened using immunoprecipitation (IPP) with [³⁵S]-methionine-labeled HeLa cell extracts. The detected protein was identified by liquid chromatography coupled with time-of-flight mass spectrometry (MS) and ion trap MS, and the corresponding proteins were confirmed as autoantigens using immunoblotting. Ab titers were measured using an enzyme-linked immunosorbent assay.

Results

A total of 113 patients received ADSC treatment, and 75% (85/113) received ADSC injection at least twice with a 6-month interval between. No obvious abnormalities were observed in any patient after their first treatment; by contrast, 53% (45/85) of patients who received their second or third ADSC injection showed severe knee arthritis. IPP detected a common anti-15 kDa Ab in synovial fluid of 62% (8/13) of the samples analyzed from patients who showed severe arthritis. This Ab was not detected in synovial fluid obtained from the same joints before treatment. The corresponding autoantigen was identified as histone H2B. All available synovial samples from patients who tested positive for anti-histone H2B Ab were newly positive after the treatment; that is, none had been positive for anti-histone H2B Ab before treatment.

Conclusions

Multiple ADSC injections for OA induced severe arthritis in a high percentage of patients, particularly after the second injection. Synovial fluid from some patients with knee arthritis contained Ab to histone H2B that appeared only after ADSC treatment. These findings provide new insights into the pathogenesis of ADSC treatment-induced severe arthritis.

Dr Eng M. Tan: a tribute to an enduring legacy in autoimmunity

At the age of ninety years, Dr Eng Meng Tan has had a remarkable impact on the accumulated knowledge of autoimmune diseases, including seminal findings in systemic lupus erythematosus (SLE) and a wide range of other autoimmune diseases. Dating to the first description of the Sm (Smith) autoantibody in SLE, his focus has been the use of autoantibodies as probes to identify and elucidate novel cellular molecules and then translating these discoveries into biomarkers and immunoassays for a wide range of these diseases and, later, cancer. He led efforts to standardize autoantibody nomenclature and testing protocols. Through his mentorship a great number of trainees and collaborators have had remarkably successful careers, and by that virtue he has garnered a remarkable continuing legacy.

Antigen specificity of antihistone antibodies in connective tissue disease patients with anti-U1RNP antibodies

To determine the prevalence of antibodies to individual histone components in collagen disease patients with anti-U1RNP antibodies. Serum samples were examined by enzyme-linked immunosorbent assay. Patients with mixed connective tissue disease (MCTD) and systemic sclerosis (SSc) showed similar levels and patterns of antihistone antibody (AHA) reactivities to individual histones: IgG responses to H2B or H3 and IgM responses to H2B were highest. However, both IgG and IgM AHAs against outer portion of chromatin (H1, H2A, or H2B) were generally higher in SLE compared with other diseases. SLE or SSc patients with anti-U1RNP antibodies showed generally higher AHA levels than in those without them. Thus, the pattern of reactivities to each histone component was dependent on the disease, while the intensity was dependent on both the disease and anti-U1RNP antibodies. The antigenic stimulus in SLE may be different from other connective tissue diseases and is more likely to be native chromatin.

[Specificities and clinical significance of autoantibodies directed against histones]

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the occurrence of numerous autoantibodies directed against nuclear antigens. Anti-histone antibodies (AHA) are as prevalent as their anti-dsDNA counterparts in SLE. Despite their frequency and potential importance, there have not been given much attention to AHA until recently. Nucleosomes, the fundamental repeating units of the chromatin, are formed of complexes of histones and DNA. The nucleosome core particle is composed of a central tetramer of 2 molecules each of H3 and H4 flanked by 2 dimers of H2A and H2B and surrounded by 2 superhelical turns of approximately 146 base pairs of DNA. The full nucleosome contains a molecule of H1 located at the point where DNA enters and exits the nucleosome. Recent studies have shown that the post transcriptional modification of histone changes chromatin structure to regulate transcription and the concept of this mechanism "epigenetics" has become center of attention in the field of basic cell biology. There have been described diverging specificities of AHA. Many attempts to locate antigenic determinants recognized by AHA have been made and H1 and H2B have been thought as common targets in lupus patients. Studies on murine models of lupus have shown several interesting findings. The universal epitope is located on H2B in (NZBxNZW)F1 mice. In addition to core histones, MRL-MP/Fas(lpr) mice develop high titers of autoantibodies to H1. Autoimmunity to chromatin regularly involves humoral immune responses directed against H1. These histones appear to be an early (possibly initial trigger) autoantigen for this autoimmune response in lupus.

Antinucleosome antibody is a major autoantibody in localized scleroderma

BACKGROUND

Localized scleroderma (LSc) exhibits autoimmunity, and antihistone antibody is frequently detected. The major antigens recognized by antihistone antibody are histones H1, H2A and H2B, which are located on the outer side of the nucleosome and are relatively more accessible for antibody binding. Therefore, it has been hypothesized that antihistone antibody is induced by nucleosome or native chromatin as immunogens in LSc.

OBJECTIVES

To determine whether antinucleosome antibody is present in patients with LSc.

METHODS

Antinucleosome antibody, antihistone antibody and antidouble-stranded DNA (dsDNA) antibody were determined by enzyme-linked immunosorbent assay. Results IgG or IgM antinucleosome antibody was detected more frequently in patients with LSc than was antihistone antibody: in 40 of 49 (82%) vs. 26 of 49 (53%), respectively. No patients had anti-dsDNA antibody. The prevalence of antinucleosome antibody positivity was comparable in the three subgroups of LSc (generalized morphoea, 89%; linear scleroderma, 71%; morphoea, 90%). Patients with systemic lupus erythematosus (SLE) exhibited a similar frequency of antinucleosome antibody positivity (13 of 15, 87%), but their IgG levels of this autoantibody were much higher than those found in patients with LSc. By contrast, IgM antinucleosome antibody levels were normal in patients with SLE, while they were significantly increased in patients with LSc compared with normal controls. Antinucleosome antibody was also detected at lower frequency in patients with systemic sclerosis (five of 20, 25%) or dermatomyositis (five of 15, 33%). Nucleosome-restricted antibodies, i.e. antibodies that react with the whole nucleosome particle but not with its individual components (histones and dsDNA) were also present in 35% of patients with LSc.

CONCLUSIONS

Although antinucleosome antibody was not specific to LSc, its high prevalence in LSc indicates that antinucleosome antibody is a major autoantibody in this disease.

Clinical relevance of autoantibodies in systemic rheumatic diseases

Autoantibodies directed to intracellular antigens are serological hallmarks of systemic rheumatic diseases. Identification of circulating autoantibodies is helpful in establishing the correct diagnosis, indicating the prognosis and providing a guide to treatment and follow-up. Some autoantibodies are included in diagnostic and classification criteria for diseases such as anti-Sm antigen and anti-double-stranded DNA antibodies in systemic lupus erythematosus, anti-U1 nuclear ribonucleoprotein antibodies in mixed connective tissue disease, and anti-SS-A/Ro and anti-SS-B/La antibodies in Sjögren's syndrome. Over the past 30 years, the identification of new autoantibody systems was advanced by the initiation or adaptation of novel techniques such as double immunodiffusion to detect antibodies to saline-soluble nuclear antigens, extraction-reconstitution and ELISA techniques to detect histone and chromatin antibodies, immunoblotting and immunoprecipitation to detect a wide range of antibodies directed against naturally occurring and recombinant proteins. These techniques have been made possible by advances in cellular and molecular biology and in turn, the sera from index patients have been important reagents to identify novel intracellular macromolecules. This paper will focus on the clinical relevance of several autoantibody systems described by Tan and his colleagues over the past 30 years.

Reactive intermediates in the oxidation of hydralazine by HOCl: the major oxidant generated by neutrophils

The use of the antihypertensive hydralazine is associated with an autoimmune syndrome resembling systemic lupus erythematosus. Adverse drug reactions, such as drug-induced lupus, often involve reactive intermediates. Oxidation of hydralazine by liver microsomes or activated leukocytes leads to reactive intermediates that covalently bind to protein and may be involved in hydralazine-induced lupus. Oxidation of hydralazine to a reactive intermediate by cells involved in immune response, such as leukocytes, would be more likely to lead to an autoimmune reaction, such as drug-induced lupus, than would oxidation by cells in the liver. Leukocytes possess a defense system that generates HOCl in response to invading microorganisms. Hydralazine was oxidized to a reactive intermediate by HOCl generated by activated leukocytes. The reactive intermediate was trapped with N-acetylcysteine and the adduct was identified as 1-phthalazylmercapturic acid. The reactive intermediate is likely the diazonium salt of hydralazine. Two stable products were formed in the reaction, phthalazine and phthalazinone. Although phthalazine is oxidized to phthalazinone by HOCl, the rate of the reaction is much too slow to explain the rapid production of phthalazinone. It is more likely that most of the phthalazinone is formed by reaction of the putative diazonium salt with water. We propose that this reactive metabolite is responsible for hydralazine-induced lupus.

Antihistone antibodies in patients with localized scleroderma

OBJECTIVE

To study the prevalence and antigen specificity of antihistone antibodies (AHA) in localized scleroderma.

METHODS

Forty-nine serum samples from patients with localized scleroderma were examined by an enzyme-linked immunosorbent assay (ELISA) and by immunoblotting.

RESULTS

By ELISA, AHA were demonstrated in 47% (23 of 49) of patients with localized scleroderma and in 87% (13 of 15) of patients with generalized morphea. Immunoblotting revealed that the predominant antigens were histones H1 and H3. The presence of AHA correlated with that of anti-single-stranded DNA antibody.

CONCLUSION

Some of the major antigens for antinuclear antibodies in patients with localized scleroderma are histones.

Autoantibodies to chromatin components in juvenile rheumatoid arthritis

OBJECTIVE

To characterize autoantibodies to chromatin components in patients with juvenile rheumatoid arthritis (JRA).

METHODS

The sera of 50 children with JRA were analyzed for antinuclear antibodies (ANA) by immunofluorescence and enzyme-linked immunosorbent assay (ELISA) techniques.

RESULTS

By immunofluorescence, ANA and antibodies to high-mobility group proteins or to DNA-free histones were common in patients with pauciarticular JRA and rheumatoid factor-positive polyarticular JRA. However, reactivity with histone-DNA complexes was rare.

CONCLUSION

Because antihistone antibodies detected by ELISA failed to bind chromatin or other histone-DNA complexes, they are not likely to represent the immunofluorescent ANA activity in serum.

Hamster female protein binding to chromatin, histones and DNA

Hamster female protein (FP) is a member of the family of proteins known as pentraxins which share amino acid sequence homology, cyclic pentameric structure and calcium-dependent binding to ligands. Other members of this family include C-reactive protein (CRP) and serum amyloid P component (SAP), and most species synthesize both CRP and SAP. FP is unusual in that it is apparently the only pentraxin produced in hamsters, it is under hormonal control and it shares binding characteristics with both CRP and SAP. CRP has been defined and isolated by its calcium-dependent binding to pneumococcal C-polysaccharide via phosphocholine (PC) residues. SAP has been isolated by calcium-dependent binding to agarose. FP binds to both PC and agarose. Recently, both SAP and CRP have been found to bind to chromatin in a calcium-dependent manner and involvement of these proteins in the clearance of nuclear material has been proposed. In this paper we test whether FP shares the ability to bind to chromatin and histones, and compare its relative avidities for these ligands. Similar to CRP, FP bound to histones H1 and H2A, and chromatin. FP shared with SAP the ability to bind to DNA. However, FP binding was inhibited by PC for all ligands, whereas SAP binding was not. FP and SAP also failed to compete with each other for binding to DNA. By cross-inhibition FP bound much less well to PC than CRP, but was a very effective inhibitor of CRP binding to H2A. These studies demonstrate that chromatin and histone binding are conserved among these pentraxins. The role of the proposed PC binding site in these binding reactions is discussed.

Autoantibodies associated with lupus induced by diverse drugs target a similar epitope in the (H2A-H2B)-DNA complex

IgG reactivity with the (H2A-H2B)-DNA complex, a subunit of the nucleosome, has been detected in many patients with lupus induced by procainamide and quinidine, but the similarity among the epitopes targeted by these antibodies in this heterogeneous patient group as well as the prevalence of this specificity in lupus induced by other drugs is unknown. Studies with histone-DNA complexes formed by sequential addition on a solid phase demonstrated that complexes containing single histones had negligible antigenicity, indicating that DNA stabilizes a protein epitope in the H2A-H2B dimer or that the complete epitope is generated by a surface feature involving H2A-H2B and DNA. F(ab')2 isolated from a patient with procainamide-induced lupus blocked greater than 90% of the anti-[(H2A-H2B)-DNA] reactivity in six of six sera from patients with lupus induced by procainamide, four of four quinidine-induced patients and in sera from patients with lupus induced by acebutolol, penicillamine, and isoniazid, but not methyldopa or auto-antibodies to the component macromolecules. Fab fragments purified from the IgG of two quinidine-induced lupus patients and patients with isoniazid- and procainamide-induced lupus retained 39% +/- 8% of their original IgG reactivity compared to 34 +/- 28% of the original anti-tetanus toxoid activity of Fab fragments in two of the same sera and two normal sera. These results indicate that anti-[(H2A-H2B)-DNA] does not require divalent antigen-antibody complexes for stability, and that the complete epitope is created by the monomeric, trimolecular histone-DNA complex. We conclude that despite their pharmacologic and chemical heterogeneity, many lupus-inducing drugs elicit near identical autoantibodies.

The role of leukocyte-generated reactive metabolites in the pathogenesis of idiosyncratic drug reactions

Evidence strongly suggests that many adverse drug reactions, including idiosyncratic drug reactions, involve reactive metabolites. Furthermore, certain functional groups, which are readily oxidized to reactive metabolites, are associated with a high incidence of adverse reactions. Most drugs can probably form reactive metabolites, but a simple comparison of covalent binding in vitro is unlikely to provide an accurate indication of the relative risk of a drug causing an idiosyncratic reaction because it does not provide an indication of how efficiently the metabolite is detoxified in vivo. In addition, the incidence and nature of adverse reactions associated with a given drug is probably determined in large measure by the location of reactive metabolite formation, as well as the chemical reactivity of the reactive metabolite. Such factors will determine which macromolecules the metabolites will bind to, and it is known that covalent binding to some proteins, such as those in the leukocyte membrane, is much more likely to lead to an immune-mediated reaction or other type of toxicity. Some reactive metabolites, such as acyl glucuronides, circulate freely and could lead to adverse reactions in almost any organ; however, most reactive metabolites have a short biological half-life, and although small amounts may escape the organ where they are formed, these metabolites are unlikely to reach sufficient concentrations to cause toxicity in other organs. Many idiosyncratic drug reactions involve leukocytes, especially agranulocytosis and drug-induced lupus. We and others have demonstrated that drugs can be metabolized by activated neutrophils and monocytes to reactive metabolites. The major reaction appears to be reaction with leukocyte-generated hypochlorous acid. Hypochlorous acid is quite reactive, and therefore it is likely that many other drugs will be found that are metabolized by activated leukocytes. Some neutrophil precursors contain myeloperoxidase and the NADPH oxidase system, and it is likely that these cells can also oxidize drugs. Therefore, although there is no direct evidence, it is reasonable to speculate that reactive metabolites generated by activated leukocytes, or neutrophil precursors in the bone marrow, could be responsible for drug-induced agranulocytosis and aplastic anemia. This could involve direct toxicity or an immune-mediated reaction. These mechanisms are not mutually exclusive, and it may be that both mechanisms contribute to the toxicity, even in the same patient. In the case of drug-induced lupus, a prevalent hypothesis for lupus involves modification of class II MHC antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies to histones in systemic lupus erythematosus: prevalence, specificity, and relationship to clinical and laboratory features

Antibodies to histones (AHA) are commonly found in patients with systemic lupus erythematosus (SLE). However, the full profile of AHA and their clinical associations remains unclear. A total of 111 patients with SLE were studied, including 13 patients in whom multiple serum samples were available over several years. IgM, IgG, and IgA antibodies to total core histones, histone complexes, and individual histones were determined by highly sensitive enzyme linked immunosorbent assays (ELISAs). Antibodies to histones were detected in 74% of serum samples, though only at low levels in half of these. Antibodies to each of the individual histones (H1, H2A, H2B, H3, H4) occurred with similar frequencies except for IgG and IgA antibodies to H4, which were uncommon. In contrast, antibodies to the histone complexes H2A-H2B and H3-H4 were detected in only two serum samples and thus do not appear to be a feature of SLE. All three major isotypes of AHA were common and usually occurred with similar frequencies to one another for the various histone specificities. There were few clinical or laboratory associations with AHA; the strongest was between IgG antibodies to total core histones and antibodies to native DNA. Similarly, there was no association between the presence of AHA and disease activity. However, for the patients as a group and in one patient alone, periods of SLE disease activity were associated with higher levels of AHA. Although the profile of antibodies to individual histones varied with time, no profile was identified that corresponded with any specific disease manifestations. It is concluded from this study that although AHA are common in patients with SLE, their clinical value in this syndrome must, at present, be considered limited.

Subnucleosome structures as substrates in enzyme-linked immunosorbent assays

Histone preparations preserving the tertiary and quaternary structure of histone-histone complexes and histone-DNA complexes, as well as individual histones, were isolated or reconstituted. Various parameters were tested in order to determine the suitability of these complexes for use as substrates in enzyme-linked immunosorbent assays. The protein concentration required to saturate the solid phase was determined, and the amount of bound protein was quantified by the micro-bicinchoninic acid protein assay. In addition, the relative DNA content of solid phase antigen was measured by the binding of monoclonal anti-native DNA antibodies. Prototype sera representing different disease groups produced reproducible and unique patterns of reactivity on the panel of antigens, demonstrating the lack of substantial assay bias. Two substrates, the H2A-H2B dimer and the H2A-H2B-DNA complex, both appear to be oriented in a random manner on the solid phase, leaving a number of different epitopes exposed to the solution. This novel set of histone antigens can now be used to define the specificity of anti-histone antibodies in relation to the quaternary structure of chromatin.

D-penicillamine-induced lupus erythematosus

We describe a patient who presented with polyarthritis, pleurisy, rash, and a positive antinuclear antibody result after 5 years of D-penicillamine therapy. D-penicillamine-induced antinuclear antibodies were mainly high-titer IgG directed against the (H2A-H2B)-DNA complex. Weak IgM activity with H1 and H2B was also observed. Withdrawal of D-penicillamine therapy resulted in improvement in clinical symptoms and gradual resolution of serologic abnormalities.

Anti-cardiolipin antibodies and HIV infection

Anti-cardiolipin antibodies of IgG class were found in 48% of intravenous drug users, 38% of homosexuals and 14% of heterosexuals (with no other risk factor) infected with HIV. Anti-cardiolipin antibodies were not increased in HIV-negative heterosexual partners of HIV-infected patients, but mildly elevated levels were detected in HIV-negative drug users, relative to healthy controls unselected for HIV status. Among HIV infected drug users, anti-cardiolipin antibodies were not associated with thrombocytopenia, Pneumocystis carinii pneumonia, disease progression or clinical stage. Anti-cardiolipin antibodies appear to be another non-specific marker of HIV infection which may be particularly common in male intravenous drug users infected with the virus.

Correlation between clinical features of systemic lupus erythematosus and levels of antihistone antibodies of the IgG, IgA, and IgM isotypes

An attempt was made to define the correlation between the clinical features of systemic lupus erythematosus and levels of circulating antihistone antibodies of the IgG, IgA, and IgM isotypes. Serum antibody levels were determined by enzyme linked immunosorbent assay (ELISA) on serial blood samples (n = 4) from 25 patients, representing five subgroups: (a) renal disease; (b) central nervous system disorders; (c) skin and joint disease only; (d) serositis; and (e) deep venous thrombosis with or without spontaneous abortion. The levels of antihistone antibodies of each isotype varied widely from patient to patient, but antibody levels in the four samples from each patient correlated closely. A close correlation between levels of IgG and IgA antihistone antibodies was found but there was no correlation between these isotypes and IgM antihistone antibodies. In individual patients no simple correlation between disease activity and antihistone antibody levels was established, but levels of antihistone antibodies of the IgG and IgA isotypes were significantly higher in those patients in whom the disease was consistently more active.

Drug metabolism by leukocytes and its role in drug-induced lupus and other idiosyncratic drug reactions

This review presents a unifying hypothesis that provides a connection between several types of hypersensitivity reactions associated with several types of drugs and explains some of the therapeutic effects (antiinflammatory activity and antithyroid effects) of these same drugs. This hypothesis centers on the oxidation of these drugs to chemically reactive metabolites by peroxidases. The drugs of interest have functional groups that are easily oxidized. The major peroxidase involved in this hypothesis is MPO because of its critical location in leukocytes which play a key role in the function of the immune system. However, thyroid peroxidase can probably also oxidize many of the same drugs to reactive metabolites, and this may be responsible for the thyroid autoimmunity observed in connection with some hypersensitivity reactions. Peroxidases have also been described in the skin and in platelets, and their presence may be responsible for the high incidence of skin reactions in the hypersensitivity response and the occurrence of immune-mediated thrombocytopenia, respectively. Involvement of other peroxidases, such as prostaglandin peroxidase, may also be important for antiinflammatory effects of drugs. In addition, leukocytes contain prostaglandin synthetase, and the activation of leukocytes leads to the release of arachidonic acid and the production of prostaglandins. This process may also lead to the metabolism of drugs to reactive metabolites. In studies of the metabolism of procainamide and dapsone, aspirin and indomethacin did not inhibit the formation of the hydroxylamine by neutrophils and mononuclear leukocytes. This is evidence against the involvement of prostaglandin synthetase in these oxidation; however, preliminary studies with other drugs suggest that prostaglandin synthetase may contribute to the metabolism of some drugs by leukocytes. Furthermore, the metabolism of phenylbutazone, phenytoin, and tenoxicam, as well as our preliminary work with other drugs such as carbamazepine, suggests that the range of drugs that are metabolized to reactive metabolites by peroxidases may be broader than initially suspected. There are several other drugs that do not fit into the functional group classes covered in this review but have similar properties. A good example is alpha-methyldopa, which is associated with drug-induced lupus, immune-mediated hemolytic anemia, and other hypersensitivity reactions. Such drugs may also be metabolized to reactive metabolites by peroxidases. Another aspect of the hypothesis is that an infection, or other inflammatory condition, may be an important risk factor for a hypersensitivity reaction because such a stimulus leads to activation of leukocytes which can lead to formation of reactive metabolites from certain drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Bullous systemic lupus erythematosus

Two patients with bullous systemic lupus erythematosus are reported. In one, the disease appears to have been caused by hydralazine. The cutaneous lesions of bullous SLE have not been previously reported in drug-induced lupus.

Drug-induced rheumatic syndromes. Diagnosis, clinical features and management

In order to avoid inappropriate therapy and prolonged morbidity, it is important to recognise when a patient's rheumatic complaints are due to drugs. However, this is often difficult because of the large number of drugs that have been implicated and the diversity of clinical presentations. Arthropathy may be seen with several different syndromes, including drug-induced lupus erythematosus (DILE), serum sickness and gout. The most widely reported of these is DILE, which usually develops after some months or even years of drug therapy. While many authors do not specifically require their presence for the diagnosis of DILE, antinuclear antibodies have been detected in the great majority of reported patients with DILE, whatever the causative drug. In contrast, patients who develop arthropathy soon after commencing a drug rarely have antinuclear antibodies and appear to be distinct from patients with DILE. Apart from arthropathy, a number of other syndromes that appear to have an immunological basis may be induced by drugs. Cutaneous vasculitis is not uncommon and drugs are frequently considered to be the aetiological factor. Whether drugs may cause larger vessel systemic vasculitis is less certain. Rarely, polymyositis and scleroderma-like syndromes have been associated with drug therapy. Corticosteroid-induced osteoporosis is a complication of all the corticosteroid preparations that are widely used at present. However, the development of deflazacort, a so-called 'bone-sparing' steroid, has raised the possibility that the effect of corticosteroids on bone may be separable, at least in part, from the other actions of these drugs. Data have been conflicting with regard to whether there is a 'safe' dose of corticosteroid. Similarly, it is unclear whether prophylactic therapy with agents such as calcium, fluoride and vitamin D is beneficial. Nonetheless, recent findings suggest that approaches will be developed to minimise the risk of osteoporosis in patients who require corticosteroids. There are a number of other ways in which drugs may affect bones. Osteomalacia is a well-known but uncommon complication of treatment with anticonvulsants and occasionally other drugs. The mechanism probably relates to the induction of hepatic enzymes and the consequent increased metabolism of vitamin D in patients with borderline levels initially. Osteosclerosis may also result from drug therapy; usually with fluoride or retinol (vitamin A) and its analogues. With continued research, the true spectrum of drug-induced rheumatic syndromes should become more clearly defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulmonary thromboembolism associated with procainamide induced lupus syndrome and anticardiolipin antibodies

Procainamide is the commonest cause of a drug induced lupus syndrome. Long term administration of this compound may induce a variety of immunological abnormalities, including antinuclear antibodies. Uncommonly, 'lupus anticoagulants' have been demonstrated in the absence of other evidence of drug induced lupus. Details of a 67 year old man who developed not only drug induced lupus but also antiphospholipid antibodies which were associated with multiple pulmonary thromboemboli after the administration of procainamide are recorded.

Methyldopa-induced systemic lupus erythematosus

Thirteen months after starting methyldopa therapy, a 55-year-old white male patient presented with a syndrome of hemolytic anemia, arthritis, photosensitivity, and a positive antinuclear antibody test result. Methyldopa-induced antinuclear antibodies were mainly IgG, directed against class H1 histones. Antibodies to native DNA and nonhistone proteins were not detected. Upon withdrawal of methyldopa therapy, and with a short course of prednisone and danazol therapy, the patient's symptoms and hemolytic anemia resolved. His clinical symptoms and serologic abnormalities returned to normal and remained negative after 2 years of followup.

In vitro anti-histone antibody production by peripheral blood cells from patients with systemic lupus erythematosus

Anti-histone antibodies (AHA) have been demonstrated frequently in the sera of patients with systemic lupus erythematosus (SLE). In the present studies, we found that peripheral blood mononuclear leukocytes (PBL) from a large subset of SLE patients spontaneously produce elevated levels of AHA in culture. In contrast, detectable production by normal mononuclear cells was extremely rare. Spontaneous production by patients' PBL correlated with both disease activity and elevated serum AHA levels, and thus appeared to reflect in vivo production. Interestingly, spontaneous AHA production was independent of polyclonal B-cell activation as measured by total Ig synthesis in culture. Production also appeared to be T-cell-independent in that cultures depleted of T cells produced AHA levels similar to those of cultures with unseparated PBL. Although PBL from normal individuals rarely produce AHA spontaneously, the presence of histone-specific B cells in normal peripheral blood could be detected after pokeweed mitogen stimulation. The present studies provide a basis for a further understanding of the mechanisms responsible for autoantibody production in SLE.

Increased presence of common systemic lupus erythematosus (SLE) anti-DNA idiotypes (16/6 Id, 32/15 Id) is induced by procainamide

Sixty-seven patients on treatment with procainamide were examined for the presence of two common idiotypes of anti-DNA antibodies (16/6 Id and 32/15 Id). These idiotypes have been shown previously to have clinical relevance in patients with systemic lupus erythematosus (SLE). An enzyme-linked immunosorbent assay (ELISA) with rabbit anti-Id antibodies revealed increased concentrations of the 16/6 Id and 32/15 Id in 25 (37%) and 16 (24%) patients, respectively. Five of eight patients with drug-induced lupus had elevated titers of both idiotypes. A high correlation (R = 0.56, P less than 0.001 for 16/6 Id) was found between Id levels and anti-single-stranded DNA (ssDNA) antibody titers and between 16/6 Id titers and antihistone antibodies (IgG, R = 0.43; IgM, R = 0.25). It seems that procainamide, a component known to be associated with drug-induced lupus, may induce an increased production of common anti-DNA idiotypes in apparently normal subjects.

Autoantigenic histone epitopes: a comparison between procainamide- and hydralazine-induced lupus

Using the technique of immunoblotting, we assessed the ability of sera from 19 patients with drug-induced lupus to bind individual histones and specific histone fragments. The pattern of histone epitopes bound by sera from 9 patients with procainamide-induced lupus was very similar to that described previously in spontaneous systemic lupus erythematosus. In contrast, sera from 10 patients with hydralazine-induced lupus bound a broader array of individual histones and recognized a different set of histone epitopes. We conclude that these 2 drugs induce antihistone antibodies through somewhat different mechanisms, which possibly involve differences in their ability to structurally alter chromatin.

Antibodies to the five histones and poly(adenosine diphosphate-ribose) in drug induced lupus: implications for pathogenesis

Certain drugs are a frequent source of antinuclear antibody (ANA) induction, and ANA is invariably present in the few patients who progress to the drug induced lupus syndrome. This report concerns the fine specificity of the ANA response to hydralazine, penicillamine, and sulphasalazine therapy. Using highly purified individual histones in fluorimetric assays, antihistone antibodies are always detectable, often in large amounts, but the pattern of response to individual histones is variable and not drug specific. In addition to the response to the three histones H1, H2B, and H3 reminiscent of idiopathic systemic lupus erythematosus, antibody to histone H2A predominates in some drug induced cases. Contrary to previous thought, histones are not the sole target of the antinuclear response: we also demonstrate a significant correlation between ANA titre and antibody to poly(adenosine diphosphate-ribose). Like the histones, this is a macromolecule that can bind to deoxyribonucleic acid (DNA). It is proposed that drug induced damage to chromatin leads to ANA production, while drug induced impairment of complement activity may then enable these autoantibodies to mediate the lupus syndrome.

Detection of anti-histone activity in sera of patients with monoclonal gammopathies

Sera from 249 patients with monoclonal gammopathies (85 multiple myeloma, 92 benign monoclonal gammopathies, 53 cryoglobulinemia, 19 Waldenström's macroglobulinemia) were examined for the presence of anti-histone activity. Thirty-four sera were found positive. In 12 of these cases the serum monoclonal immunoglobulins were purified and in all, the anti-histone activity appeared to reside in the monoclonal component. None of the patients had symptomatology of lupus despite high titers of anti-histone activity. This study demonstrates an anti-histone activity of monoclonal components of patients with monoclonal gammopathies.

Detection of antibodies to total histones and their subfractions in systemic lupus erythematosus patients and their asymptomatic relatives

Sera drawn from 75 patients with systemic lupus erythematosus, 141 healthy relatives (from the families of 51 patients), and 115 healthy control subjects were examined, by enzyme-linked immunosorbent assay, for IgG and IgM antibodies to total histones and their subfractions. Compared with the controls, statistically significant numbers of patients and their relatives had antihistone antibodies of both isotypes. Among the relatives, the sera from females, notably sisters of the patients, contained the highest levels of anti-total histone antibody. Anti-H2A/H2B and H3 antibodies were most prevalent among the lupus patients, but many of the relatives had IgM anti-H4 antibodies. These findings indicate that antihistone antibodies can serve as a genetic marker in patients with systemic lupus erythematosus.

Measurement of serum DNA binding in chronic active hepatitis and systemic lupus erythematosus using the Farr assay

Antibodies to double-stranded DNA (dsDNA), generally regarded as highly specific for systemic lupus erythematosus (SLE), have also been reported in chronic active hepatitis (CAH). Using the Farr assay and E. coli DNA, fractionated by benzoylated-naphthoylated-DEAE cellulose chromatography into dsDNA and dsDNA containing single-stranded regions, we compared the serum DNA binding of CAH and SLE patients. Although CAH sera were found to have dsDNA binding significantly above the normal control group such binding was of low level and we could find no evidence of markedly elevated dsDNA binding in CAH. However 12 of the 20 CAH sera studied did bind preferentially to dsDNA containing single-stranded regions suggesting the presence of anti-single-stranded DNA antibodies. We conclude that the description of elevated anti-dsDNA antibodies, as measured by the Farr assay, in CAH is due to the interaction of anti-single-stranded DNA antibodies or other serum components with single-stranded DNA contaminating dsDNA preparations.

Specificity of acebutolol-induced antinuclear antibodies

Treatment with the beta blocker acebutolol may trigger antinuclear antibody (ANA) production. We retrospectively studied 97 sera from 47 patients who developed ANA during acebutolol treatment. Anti-histone and anti-denatured (ss) DNA antibodies were found in 53% and 66% respectively of the sera tested. The activities of these two antibodies correlated well with the total ANA titer. Anti-native (ds) DNA were absent or present at low titer. This immunochemical pattern of acebutolol-induced ANA is similar to that reported for other drug-induced ANA. To date, the presence such isolated ANA is not known to expose patients to any particular risk other than exceptional and minor clinical manifestations of lupus which are rapidly reversible following therapy cessation.

No demonstrable relationship between IgM and IgG antinuclear antibody levels and acetylator phenotype in patients with systemic lupus erythematosus

To ascertain the possible influence of acetylator phenotype on antinuclear antibodies in systemic lupus erythematosus (SLE), we assayed sera from 11 rapid acetylators and 10 slow acetylators for IgM and IgG antibodies to chromatin, histones, denatured DNA, and native DNA. Whereas the majority of SLE patients of both acetylator phenotypes had elevated levels of antibodies to all 4 antigens compared with normal controls, there was no difference in antibody activities between slow acetylator patients versus rapid acetylator patients for these antigens. We conclude that levels of antibody to chromatin, histones, and DNA in SLE patients are similar irrespective of acetylator phenotype, and that if a protective effect of slow acetylation on spontaneous development of antinuclear antibodies does occur, a prospective study of presymptomatic individuals at high risk for lupus may be required to reveal this effect.

IgG antibodies to the histone complex H2A-H2B characterize procainamide-induced lupus

Patients treated with procainamide and other drugs commonly develop antinuclear antibodies and occasionally symptoms of lupus erythematosus. However, the pathological events which lead to clinical symptoms in some patients but only abnormal serology in others have not been established. The present study examines the incidence, amount, immunoglobulin class, and antigen-binding specificity of anti-histone and anti-denatured DNA (anti-dDNA) antibodies in three groups of patients. These comprised a prospective study of patients treated with procainamide, patients with clinical drug-induced lupus symptoms, and a group undergoing therapy for many years without any symptoms. Procainamide elicited IgG and IgM anti-dDNA antibodies concordantly. Anti-histone IgM antibodies also appeared de novo during this period but IgG anti-histone antibodies were detected less frequently. Asymptomatic patients tended to have an antibody profile consisting of highly elevated anti-dDNA, IgM antibodies reactive with all histones and IgG antibodies specific for only one or two histone classes. In contrast symptomatic patients usually had little anti-dDNA or antibodies to individual histones but had pronounced IgG antibodies to the histone complex H2A-H2B. This unique antibody was characteristics of procainamide-induced lupus and was not detected in patients whose disease was induced by hydralazine. Anti-(H2A-H2B) decreased after procainamide was discontinued, concomitant with subsidence of symptoms. The finding that autoantibodies elicited by procainamide in patients with lupus symptoms have a characteristic immunoglobulin class and specificity may be of pathogenic significance and suggests that patients susceptible to procainamide-induced lupus have a unique immune response. In addition, this information could be of diagnostic value in predicting which procainamide-treated patients will develop overt symptoms of lupus.

Antinuclear antibodies in autoimmune disease. Significance and pathogenicity

A large number of antigen-antibody systems have been described in association with connective tissue diseases. However, with the exception of antibodies to dsDNA, none of them have yet been successfully implicated in the pathogenesis of autoimmune diseases. It is also unclear why specific ANA are associated just with certain diseases, for example, anti-Sm with systemic lupus erythematosus. Although many questions remain about what triggers ANA production and whether these antibodies are innocent bystanders or disease inducers or enhancers, ANA serology can still be very useful to the clinician.

Patterns of antihistone antibody specificity in systemic rheumatic disease. I Systemic lupus erythematosus, mixed connective tissue disease, primary sicca syndrome, and rheumatoid arthritis with vasculitis

A new fluorimetric assay was used to measure the relative amounts of antibodies to individual nuclear histones in sera from 102 patients with systemic lupus erythematosus (SLE), mixed connective tissue disease, primary sicca syndrome, and rheumatoid arthritis with vasculitis. In SLE sera, the predominant responses were to histones H-1, H-2B, and H-3, with marked elevations of binding to H-1 and H-2B in one-third of the patients, and to H-3 in one-fourth; antibodies of both the IgG and IgM classes were also detected. In a few SLE sera, the pattern of histone response differed or was restricted to 1 immunoglobulin class. In mixed connective tissue disease, only 2 of 9 sera showed elevated histone binding activity, the response being predominantly to H-3 in 1 patient and to H-1 and H-2B in the other. Binding to H-2B was also prominent in 2 of 3 patients with primary sicca syndrome. The highest antihistone reactivity and the most heterogeneous response patterns were observed in patients who had rheumatoid arthritis with vasculitis; 6 of 8 of those sera had elevated histone reactivity. In SLE, the highest histone binding results were found among patients with a history of photosensitivity. Histones are closely associated with DNA in the nucleosome, and we speculate that antihistone antibodies could arise as a result of damage to DNA, induced by drugs or irradiation.

The binding of antihistone antibodies to Crithidia luciliae kinetoplasts is growth cycle-dependent

The Crithidia luciliae immunofluorescence (CLIF) assay is widely used to test for native DNA (nDNA) antibodies in the diagnosis and management of systemic lupus erythematosus. However, sera from patients with drug-induced lupus erythematosus or rheumatoid arthritis, which should not contain nDNA antibodies, occasionally react with the CL kinetoplast. We examined 36 sera from patients with systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, and drug-induced lupus erythematosus, who had positive CLIF tests. All 36 sera were also antinuclear antibody-positive with homogeneous and/or peripheral staining patterns on mouse kidney substrates. After hydrochloric acid extraction of the CL smears to remove histone and other nuclear protein antigens, 14 of the 36 sera no longer produced a positive result on the CLIF test. Ten of these 14 sera again gave a positive CLIF result after the hydrochloric acid-extracted Crithidia substrate had been reconstituted with purified histone. These studies demonstrated that kinetoplast binding was due to antihistone antibodies in at least 10 of 36 initially CLIF-positive sera. Antihistone antibodies were then purified with a histone-affinity column, and these purified antibodies were reactive with CL kinetoplasts. Thus, the CLIF test is not specific for nDNA antibodies. Additional studies using CL from different days of culture indicated that histone antigen expression in the CL kinetoplast was a function of the life cycle of this organism and is most readily detected 2 days after initiation of culture.

The diagnostic value of antihistone antibodies in drug-induced lupus erythematosus

This study was undertaken to see whether the presence of antihistone antibodies, measured by indirect immunofluorescence assay, could distinguish between patients who were symptomatic from a drug-induced lupus-like illness (DILE) and asymptomatic patients who had drug-induced antinuclear antibodies (DANA). In this study, 82% of the patients with DILE had antihistone antibodies detectable in their sera, compared with 32% of the patients in the DANA group (P less than 0.01). When the patients taking procainamide were analyzed separately, it was found that 92% of the patients with DILE had demonstrable antihistone antibodies, contrasted with 33% of the patients in the DANA group (P less than 0.01). In those patients with antihistone antibodies (DILE versus DANA patients), there were no differences in the mean antibody titers. We conclude that the presence of antihistone antibodies is strong, statistically significant evidence that the symptoms of a given patient are due to drug-induced lupus erythematosus.

Reevaluation of specificity of Crithidia luciliae kinetoplast as a substrate for detecting antibodies to double-stranded deoxyribonucleic acid

Until now, the kinetoplast of the hemoflagellate Crithidia luciliae has been believed to be a specific indirect immunofluorescence substrate for detecting antibodies to double-stranded deoxyribonucleic acid (DNA). We have recently identified a patient in whom there was the apparent presence of procainamide-induced antinuclear antibodies at a titer of 1/1,280 on mouse kidney sections. This patient's serum also contained antihistone antibodies at a titer of 1:1,280, on the basis of a mouse kidney section histone reconstitution assay. In addition, results of an enzyme-linked immunosorbent assay (ELISA) using a pure histone preparation were strongly positive. We found that this serum produced C. luciliae fluorescence to a titer of 1:80. After pretreatment of the C. luciliae substrate with hydrochloric acid to remove histones, this serum no longer produced kinetoplast fluorescence. However, this serum again produced kinetoplast fluorescence when assayed on a hydrochloric acid-treated C. luciliae substrate that had been reconstituted with purified histone. The negative kinetoplast reactivity after hydrochloric acid treatment of the C. luciliae substrate suggests that the antibody is reacting with acid-extractable nucleic acids, not necessarily the double-stranded DNA, or the antibody is directed against nuclear proteins such as DNA-histone complexes of deoxyribonucleoprotein. The finding that reactivity reappeared after the histone was reconstituted back to the hydrochloric acid-treated C. luciliae substrate suggests that the primary antibody in this serum is directed against DNA-histone complexes or histone alone. These findings strongly suggest that the kinetoplast of C. luciliae contains antigens other than double-stranded DNA and that is not a specific substrate for the detection of double-stranded DNA antibodies by indirect immunofluorescence.