Are there environmental forms of systemic autoimmune diseases?

A large number of drugs and an increasing number of environmental agents reportedly result in the appearance of a number of autoantibodies and in many instances in the appearance of a range of autoimmune clinical syndromes. The major disorders so recognized have marked resemblances to the autoimmune disease systemic lupus erythematosus. The commonly used term is drug-induced lupus; a better term is drug-related lupus. There is considerable interest at the present time in an increasing number of environmental agents. There have been two epidemics in recent years--one in Spain to a contaminant of rapeseed oil and one in the United States to a contaminant of l-tryptophan that caused an eosinophilic myositis. It is important for physicians and others involved in health care to recognize the potential associations of these diseases of unknown cause or causes.

Human autoantibodies recognizing a native macromolecular structure composed of Sm core proteins in U small nuclear RNP particles

OBJECTIVE

Monoclonal antibody (mAb) F78 recognizes a heat-labile particle composed of Sm core proteins designated F78P. The objective of this study was to identify human autoantibodies recognizing the conformational structure of F78P.

METHODS

Immunoblots using HeLa cell extracts without heating prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to identify autoantibodies recognizing F78P. To confirm reactivities with F78P, immunoprecipitates of mAb F78 were used as a substrate for immunoblots. To identify reactivities against the F78P structure in classic anti-Sm-positive sera, autoantibodies to individual Sm core proteins were absorbed with purified U1 small nuclear RNP before immunoblotting.

RESULTS

We identified 2 sera that, like F78, recognized only F78P and not its component polypeptides. When classic anti-Sm antibodies were preabsorbed, the presence of F78-like, particle-specific antibodies was revealed in all of the anti-Sm-positive sera tested.

CONCLUSION

Autoantibodies against the F78P structure were commonly present in sera from patients with systemic rheumatic diseases, often in combination with4=1998 M autoantibodies.

Association of osteonecrosis in systemic lupus erythematosus with abnormalities of fibrinolysis

Patients with systemic lupus erythematosus (SLE) are at an increased risk of developing osteonecrosis (ON). Twenty-six patients with SLE were studied. Fifteen of these had ON and 11 did not. The latter were used as control subjects. Various coagulation analytes including antithrombin III (ATIII) activity, protein C activity, protein S activity, alpha 2-antiplasmin activity, anticardiolipin antibodies (aCL), plasminogen activator inhibitor (PAI-1) activity and tissue type plasminogen activator (tPA) antigen were measured using citrated plasma samples from the patients. A significant proportion (80%) of patients had at least one laboratory abnormality that has been associated with a thrombotic predisposition. ON was significantly associated with elevated levels of PAI-1 activity; it was also associated with elevated PAI-1/tPA ratio. There was no association between ON of SLE and abnormalities of the other measured coagulation analytes. These results suggest that defective fibrinolysis seems to be operative in the pathogenesis of ON associated with SLE. The defect appears to involve an imbalance between tPA and its inhibitor, PAI-1. This imbalance could represent an important risk factor in the pathogenesis of ON.

Genetic and immunologic studies of patients on procainamide

Forty (40) patients with cardiac arrhythmias receiving procainamide (PA) therapy and 24 patients who were receiving other drugs for their cardiac disorders were investigated for class II HLA phenotypes and their DRB1*04 and DQB1*03 subtypes. Other genetic marker evaluations in the PA patients included: 1) class III MHC C4A and C4B null alleles of complement; and, 2) acetylation phenotype. Twenty (20) of the PA patients were also tested for the ability of their stimulated cells to secrete Interleukin-1 (IL-1 beta) and tumor necrosis factor (TNF alpha). We also examined the spontaneous production of these cytokines by peripheral blood leukocytes (PBL) from patients who were receiving chronic PA treatment. The results revealed no association of acetylation phenotypes with the class II HLA phenotypes nor class III MHC C4 allotypes in these patients. The results did show a significant increase in class III C4 complement allotypes in the PA patients when compared to the controls. The results also showed a significant increase in autoantibodies and DQw3 phenotypes in the PA patient group when compared to control populations. Results of spontaneous IL-1 and TNF production suggested there may be an association of select class II HLA phenotypes in some patients and this may be relevant to host responsiveness to PA treatment.

Accelerated atherosclerosis and coronary disease in SLE

Atherosclerosis may represent a significant cause of death and morbidity in patients with systemic lupus erythematosus. Coronary involvement is more premature in lupus patients. We present the case of a young woman diagnosed with SLE at the age of 20 years who had a myocardial infarction at age 29 years. We review the mechanisms of atherosclerosis, the interrelations between atherosclerosis and autoimmunity, and between atherosclerosis and SLE. We also review the risk factors, influence of disease and treatment and the guidelines for management of accelerated atherosclerosis in lupus patients.

Reversible parotid enlargement and pseudo-Sjögren's syndrome secondary to hypertriglyceridemia

We describe 2 patients with a Sjögren-like syndrome apparently secondary to hypertriglyceridemia. Both had bilateral parotitis in addition to musculoskeletal and sicca symptoms. Parotid gland histology revealed fatty infiltration with no inflammation. Therapy with dietary modification and triglyceride lowering drugs resulted in resolution of symptoms and parotid swelling in one patient. In the 2nd patient, hypertriglyceridemia was resistant to triglyceride lowering drugs, and parotid symptoms and swelling continued unabated. Our findings suggest aggressive treatment of hyperlipidemia in pseudo-Sjögren's syndrome may result in amelioration of musculoskeletal and parotid symptoms.

Triplex-DNA stabilization by hydralazine and the presence of anti-(triplex DNA) antibodies in patients treated with hydralazine

Hydralazine is an antihypertensive drug that elicits andti-nuclear antibodies in patients as an adverse effect. We investigated the ability of hydralazine to promote/stabilize the triplex DNA form of poly(dA).2poly(dT). Under conditions of low ionic strength, the polynucleotide melted as a double helix with a melting temperature (Tm) of 55.3 degrees C. Hydralazine destabilized this duplex form by reducing its Tm to 52.5 degrees C. Spermidine (2.5 microM), a natural polyamine, provoked the triplex form of poly(dA)-.2poly(dT) with two melting transitions, Tm1 of 42.8 degrees C corresponding to triplex-->duplex+single-stranded DNA and Tm2 of 65.4 degrees C, corresponding to duplex melting. Triplex DNA thus formed in the presence of spermidine was further stabilized by hydralazine (250 microM) with a Tm1 of 53.6 degrees C. A similar stabilization effect of hydralazine was found on triplex DNA formed in the presence of 5 mM Mg2+. CD spectra revealed conformational perturbations of DNA in the presence of spermidine and hydralazine. These results support the hypothesis that hydralazine is capable of stabilizing unusual forms of DNA. In contrast with the weak immunogenicity of DNA in its right-handed B-DNA conformation, these unusual forms are immunogenic and have the potential to elicit anti-DNA antibodies. To test this possibility, we analysed sera from a panel of 25 hydralazine-treated patients for anti-(triplex DNA) antibodies using an ELISA. Our results showed that 72% of sera from hydralazine-treated patients contained antibodies reacting toward the triplex DNA. In contrast, there was no significant binding of normal human sera to triplex DNA. Taken together our data indicate that hydralazine and related drugs might exert their action by interacting with DNA and stabilizing higher-order structures such as the triplex DNA.

Etiology, environmental relationships, epidemiology, and genetics of systemic lupus erythematosus

The etiology of systemic lupus erythematosus (SLE) and the many lupuslike syndromes continues to challenge investigators. Focus is now on the role of heat-shock proteins, apoptosis, the possible role of diet factors, and in particular, the role of lipids. The role of various infections as either triggering mechanisms or in contributing to morbidity is receiving close attention. In particular, retroviruses are being carefully studied with all the molecular tools available. This area has real promise and carries with it the possibility of anti-infection treatments. Considerably more attention is being paid to the hormonal aspects of SLE and their modulation of the immune system. Environmental associations continue to intrigue investigators and clinicians, and both drugs and other environmental factors provide excellent investigational models. We continue to need good prevalence and incidence studies. Genetically, there is an increasing sophistication in the type of studies, and the ensuing data may well provide real insights into various subsets of SLE.

Epidemiology, genetics, etiology, and environment relationships of systemic lupus erythematosus

Systemic lupus erythematosus continues to provide a major etiologic challenge. Current investigation is focusing on the possibilities of environmental factors, including infection. How these factors are related to genetic factors, including the major histocompatibility complex and more recently observed defects in apoptosis genes, remains unclear. Ethnic and geographic studies of systemic lupus erythematosus are providing important clues, as are continued clinical observations on the various subsets of disease and the patterns of therapeutic response. Different pathogenic mechanisms are constantly being uncovered and in turn need to be related to the various etiologies.

Alterations in human endothelial cell morphology, proliferation and function by a macrophage-derived factor

Changes in endothelial cell (EC) morphology occur at sites of physiological lymphocyte traffic and in areas of chronic inflammation. Previous studies have shown that EC shape changes also occur in vitro following exposure of EC monolayers to peripheral blood mononuclear cell (PBMC)-derived conditioned media (CM). In the present study, quantitative image analysis is used to define the cell of origin of the elongating factor(s), to examine changes in EC proliferation and function accompanying PBMC-induced human EC elongation and to identify the active PBMC-derived products responsible for this elongation. By separating mononuclear cells into subpopulations (macrophages, B cells and T cells) and adding conditioned media derived from these subpopulations to cultured ECs, the macrophage (M phi) is shown to be the primary cell of origin of the elongating factor(s). Furthermore, EC elongation is accompanied by both a dose-dependent decrease in cellular proliferation and an increase in prostacyclin production. These findings suggest that PBMC-induced changes in EC morphology may be associated with a shift from a proliferative state to a more secretory phase of the EC cycle. Finally, using recombinant factors it is shown that TNF alpha acting in combination with IL-1 may be the active PBMC-derived products which contribute to EC elongation.

Nonsteroidal antiinflammatory drug modulation of prosthesis pseudomembrane induced bone resorption

OBJECTIVE

To study the in vitro effect of therapeutic levels of select nonsteroidal antiinflammatory drugs (NSAID) on prosthesis associated pseudomembrane induced bone resorption and cytokine and prostanoid synthesis using tissue obtained from osteoarthritic patients undergoing revision of cemented implants.

METHODS

Pseudomembranes were cultured in the presence and absence of therapeutic levels of select NSAID: Processed conditioned media were evaluated for bone resorbing capacity by assessing murine neonatal limb rudiment release of 45Ca. Interleukin 1 (IL-1) and tumor necrosis factor (TNF) were analyzed by bioassay and prostaglandin E2 (PGE2) by radioimmunoassay.

RESULTS

Piroxicam, in contrast to indomethacin and sodium salicylate, significantly decreased membrane associated bone resorption. The NSAID effect correlated more consistently with piroxicam downregulation of TNF synthesis than that of IL-1. Consistent drug associated suppression of PGE2 synthesis did not enable differentiation of NSAID effectiveness in suppressing pseudomembrane induced bone resorption.

CONCLUSION

Results provide a rational basis for design of animal models and/or further human studies to test the hypothesis that the prophylactic administration of an NSAID can potentially retard the pseudomembrane effected bone resorptive process associated with aseptic cemented prosthesis failure.

Study of procainamide hapten-specific antibodies in rabbits and humans

Procainamide (PA) is the drug most commonly associated with the induction of autoantibodies and drug-related lupus (DRL). While the majority of these patients express autoantibodies, antibodies to the parent drug and metabolites, PA-hydroxylamine (PAHA) or nitroso-PA (NOPA), have not been reported in humans. Hapten-carrier conjugates were prepared using human hemoglobin (HgB) or autologous rabbit erythrocytes with PAHA or NOPA. PA was conjugated to rabbit serum albumin (RSA) or egg albumin (OVA) via diazotization and condensation methods. Rabbits were immunized with hapten conjugates in Freund's adjuvant. These hapten-carrier compounds (5-10 micrograms/ml) were used as test antigens for antibodies in sera from the rabbits and 40 patients on chronic PA treatment. 10 SLE patients, 33 elderly and 20 young normal controls by ELISA. Type I and II collagens were also used as test antigens for human sera. Sera from rabbits immunized with the PA compounds had elevated IgG antibody values to PA, PAHA and NOPA, but no autoantibodies. Absorption of the rabbit sera with the PA compounds reduced the antibody levels; ssDNA and histones failed to inhibit the total binding values. Mean binding to PA-OVA was 0.95 +/- 0.41 for PA patients and 1.37 +/- 0.26 standard error of means (S.E.M.) in the SLE patients compared to 0.37 +/- 0.14 S.E.M. in the normal sera (P < or = 0.05); similar binding values to PAHA-HgB and NOPA-HgB were also observed. Sixty-eight percent of the PA patients had antibodies to type II collagen. Elevated binding values to PA compounds were inhibited by absorption of human sera with ssDNA or total histones; absorption with PA or PAHA had no significant effect. These findings suggest that sera from PA patients containing high titers of autoantibodies cross-react in vitro with unrelated antigens.

Hydralazine induces Z-DNA conformation in a polynucleotide and elicits anti(Z-DNA) antibodies in treated patients

We studied the effect of hydralazine, an antihypertensive drug with lupus-inducing side effects, on the conformation of poly(dG-m5dC).poly(dG-m5dC) and a plasmid with a 23 bp insert of (dG-dC)n.(dG-dC)n sequences. Using an e.l.i.s.a. with a monoclonal anti-(Z-DNA) antibody Z22, we found that hydralazine provoked the Z-DNA conformation in poly(dG-m5dC).poly(dG-m5dC) at 250-500 microM concentration. The supercoiled form of hydralazine-treated plasmid bound to Z22 in a gel-retardation assay. To examine further whether Z-DNA could act as an inciting agent in anti-nuclear antibody production in patients, we analysed 65 sera from 25 hypertensive patients taking hydralazine and found anti-(Z-DNA) antibodies in 82% of these sera. Sera from age-matched normal controls showed no binding to Z-DNA. Data on sera drawn sequentially from four hypertensive patients showed that antibodies were present after the drug treatment. These data demonstrate the presence of a high incidence of anti-(Z-DNA) antibodies in patients treated with hydralazine and suggest that a possible mechanism for the production of autoantibodies in drug-related lupus might involve the induction and stabilization of Z-DNA by drugs.

Erosive osteoarthritis

Erosive osteoarthritis is a disorder that most often involves the hands of postmenopausal women. It can begin abruptly with pain, swelling, and tenderness. Distal interphalangeal joints are involved most frequently, followed by proximal interphalangeal joints. Occasionally there is metacarpophalangeal, carpal, or large joint involvement. The female-to-male ratio is approximately 12:1. There are no known HLA associations. Laboratory studies generally are negative. A mild elevation of the sedimentation rate may occur. Radiologically, the disorder is characterized by central erosions and the "gull wing" deformity. Synovial pathology has shown changes consistent with both rheumatoid arthritis and osteoarthritis and manifests the stage of disease at the time of biopsy. The etiology remains obscure, but hormonal influences, metabolic disorders, and autoimmunity have been implicated. Treatment is largely supportive with physical therapy, nonsteroidal antiinflammatory drugs, and occasionally prednisone. Overall prognosis is good, although deformity and impairment of hand function may occur. For this reason, a reassessment of treatment strategies may be in order.

Rheumatic diseases and AIDS--is the association real?

There have been many reports of an association of certain musculoskeletal disorders especially Reiter's syndrome and psoriatic arthritis with human immunodeficiency virus (HIV) infection. A review of the first 1,100 HIV positive patients at the University of Cincinnati AIDS Clinic and Treatment Center has revealed 9 with psoriasis of whom 4 developed arthritis, 1 with Reiter's syndrome which predated HIV infection, 9 with nonspecific arthralgias, 7 with diffuse myalgias of whom 5 were AZT and one alpha-interferon related. Three patients with temporal arteritis/polymyalgia rheumatica, 2 of whom are biopsy proven, have been observed. The frequency distribution for race, age, sex for this population was contrasted to that expected. The only increased frequencies were in psoriatic arthritis with 4 cases observed and 0.73 expected and in temporal arteritis/polymyalgia rheumatica with 3 cases observed and 0.3 expected. Whether there is a coincidental or real increase is an important question requiring prospective, epidemiological studies to help determine if the differences reported are demographic or genetic.

Genetic, immunologic and biotransformation studies of patients on procainamide

This report represents follow-up observations of a unique long-term study of patients on procainamide (PA) for various cardiac arrhythmias. Serologic and clinical evaluations associated with drug-related autoimmunity were assessed and patients were characterized for factors postulated to influence susceptibility to autoimmunity, including acetylator phenotype, oxidative metabolism of PA, HLA class profile, and production of interleukin-1 (IL-1) and tumor necrosis factor (TNF). Fifty-two percent had IgM and 70% IgG antibodies to total histones; 67% had IgG antibodies to histone H2A/H2B. Patients were equally divided between fast and slow acetylators. N-oxidative metabolism of PA was indicated by the presence of urinary nitroprocainamide, which correlated with elevated titers of antihistone antibodies. There was a significant incidence of the DQw7 split of DQw3 in PA patients when compared to controls, and the frequency of antibodies to total histones and H2A/H2B was significantly increased in the DQw7 patients. C4A*QO and C4B*QO alleles were more frequent in the PA patients than in controls. IL-1 and TNF production was not different in patients compared to controls. These data suggest that certain genetic factors may serve as markers for PA-related autoimmunity.

Dicyanogold (I) is a common human metabolite of different gold drugs

Gold based drugs and their metabolites have been characterized using reversed phase, ion pairing chromatography with an inductively coupled plasma mass spectrometer as an element specific detector. For a patient receiving gold sodium thiomalate the principal gold species in the urine is [Au(CN)2]-, which is also seen in a low molecular weight infiltrate of the blood. The same compound is also identified in the urine and blood of a patient taking auranofin and in patients taking solganol. This represents the first identification of a specific gold metabolite in biological fluids taken from patients undergoing gold therapy and the first evidence that different gold drugs have common metabolites.

Role of drugs and environmental agents in lupus syndromes

It is increasingly accepted that a broad range of drugs and environmental factors can give rise to lupus syndromes and other types of connective tissue disease syndromes. This chapter reviews the drugs and environmental agents reported during this past year. Considerable research efforts are now focused on understanding the possible mechanisms, particular specificities of the antibody responses, new patterns of antibody responses, and biochemical pathways. These potentially important contributors to the expression of disease are reviewed.

Serologic evaluation of patients receiving procainamide

This controlled study examined the characteristics of serologic abnormalities in 52 patients receiving procainamide for cardiac arrhythmias, who had no symptoms of a connective tissue disease. Antinuclear antibodies occurred in 43 patients (83%). Significant elevation of antibody binding to single-stranded DNA (mean +/- SEM 30 +/- 2.6%), double-stranded DNA (13 +/- 1.1%), Z-DNA (optical density 0.54 +/- 0.06), and poly A (7.2 +/- 0.6%) was seen (P less than 0.001). Thirty-four patients (65.4%) had antibodies to total histones, most frequently, the H2A/2B dimer. IgG antibodies to H2A/2B correlated with the cumulative procainamide dose. One patient subsequently developed drug-related lupus.

Drug-related lupus. Incidence, mechanisms and clinical implications

Adverse side effects to drugs and chemicals in which immune mechanisms may be responsible have been described in drug-related lupus (DRL). The spectrum of drugs that may elicit DRL includes such classes as the hydrazines, arylamines, and chemicals that can be metabolised to amines. The 2 major pathways of metabolism--acetylation and N-hydroxylation--are described in detail. The events leading to autoantibody production are not well understood; however, specific consideration of the genetic makeup of patients who are candidates for treatment with these drugs may help identify those at risk of developing DRL.

Drug-related lupus

All physicians should be alerted to the many drugs and other agents that are associated with drug-related lupus, as there is an increasing number of such drugs. A wide range of immune responses and antibodies are being reported with this syndrome. A new concern is the perceived ability of new biologic treatments to induce these autoimmune phenomena. More in-depth studies of various environmental factors are providing new insights into possible mechanisms. These include the immune responses to the drugs, their metabolites, and drug-altered conjugates; bioactivation mechanisms of drug protein conjugation; the role of macrophages in antigen recognition and processing; and lastly, the important role of the acetylation of various drugs and the relationship to immunogenetic factors. Continued study of this human experimental model of lupus will help to clarify the etiology and mechanisms of systemic lupus erythematosus itself.

Determination of metabolically derived nitroprocainamide in the urine of procainamide-dosed humans and rats by liquid chromatography with electrochemical detection

The N-oxidized metabolites of the antiarrhythmic procainamide have previously been implicated as inciting agents in the autoimmune condition drug-related lupus. Although much data have been collected with respect to the in vitro behavior of these metabolites, relatively little has been accomplished in vivo because of their extreme reactivity. The determination of nitroprocainamide (NPA), a stable decomposition product of the reactive hydroxylamine and nitroso species, in the urine of rats dosed with procainamide is reported here using the sensitive and selective method of HPLC with electrochemical detection. For orally and i.v.-dosed animals, up to microgram amounts of NPA were excreted over 24 hr from an initial dose of 66-100 mg procainamide/kg body weight. Also, the apparent elimination of microgram quantities of NPA in the urine specimens of 9 of 11 patients undergoing treatment with procainamide was observed. This suggests that N-oxidation of the aromatic ring of procainamide is occurring at sufficient levels to result in the formation of significant amounts of the reactive hydroxylamine and nitroso metabolites in vivo, and may have direct implications in the diverse and widespread symptomatology associated with procainamide-induced drug-related lupus.

NSAID induction of interleukin 1/catabolin inhibitor production by osteoarthritic synovial tissue

Select classes of nonsteroidal antiinflammatory drugs (NSAID), independent of their cyclooxygenase suppressing property, may potentially regulate pathophysiologic mechanisms operative in accelerated cartilage catabolism occurring in osteoarthritis (OA). Piroxicam has been shown to downregulate the expression of interleukin 1 (IL-1) associated chondrocyte enzyme inducing activity (catabolin) produced by OA synovium. In situ membrane synthesis of catabolin/IL-1 inhibitors functioning at various levels in thymocyte and catabolin bioassay systems is currently shown. The piroxicam effect appears due to a selective increase in production of a naturally occurring inhibitor(s) and/or induction of new inhibitor formation acting on chondrocytes at a post-IL-1 receptor level.

Induction of autoantibodies by human immunodeficiency virus infection and their significance

Although many of the changes in HIV and AIDS appear to be global, on closer investigation the defects are specific and can be explained by recognized mechanisms. Despite a demonstrated concurrent polyclonal B-cell activation, studies fail to show any evidence to date of significant dysregulation of the immune system leading to serologic or clinical autoimmunity.

Effects of procainamide hydroxylamine on generation of reactive oxygen species by macrophages and production of cytokines

A series of experiments was conducted to examine the effects of the N-oxidized metabolite of procainamide, procainamide hydroxylamine (PAHA), on reactive oxygen species (ROS) production by macrophages in vitro, as well as on the release of the cytokine interleukin-1 (IL-1). Results with PAHA were compared with those from the parent compound, procainamide, and in some cases with other procainamide metabolites such as N-acetylprocainamide or nitrosoprocainamide. The effects of PAHA on ROS production by mouse and rat macrophages were complex, resulting in both stimulatory and inhibitory activity depending upon the PAHA concentration and whether macrophages were resting or elicited. The primary effect of PAHA appeared to be a stimulation of ROS production. Monocytes pretreated with PAHA (20 microM) depressed the responsiveness of lymphocytes in co-culture to a T-cell mitogen (conconavalin A) but not a B-cell mitogen (lipopolysaccharide). This effect was inhibited when monocyte pretreatment with PAHA was accompanied by the antioxidants, catalase or superoxide dismutase. IL-1 production by rat adherent splenocytes was unaffected by PAHA in concentrations that were not cytotoxic. These observations suggest that the oxidative metabolism of procainamide to PAHA may result in enhanced production of ROS by macrophages contributing its toxicity to lymphocytes.

Nonsteroidal antiinflammatory drugs in rheumatoid arthritis: duration of use as a measure of relative value

To determine if any nonsteroidal antiinflammatory drug (NSAID) was superior in the treatment of rheumatoid arthritis, duration of use of each drug was employed as a measure of combined efficacy and tolerability. Duration was treated as survival data and a proportional hazards model utilized to adjust for differences in disease severity and concomitant antirheumatic therapy. One hundred and sixteen patients took 188 courses of nonsalicylate NSAID during the 3-year study period. The NSAID prescribed included naproxen, ibuprofen, sulindac, indomethacin, piroxicam, and tolmetin. Naproxen was used significantly longer than any other NSAID (p less than 0.001).

Immunomodulatory effects of procainamide metabolites: their implications in drug-related lupus

Evidence suggests that N-oxidized metabolites of procainamide may be responsible for the development of lupus-like symptoms associated with procainamide therapy. The human hepatic microsomal metabolism of procainamide has been previously reported to result in formation of the N-hydroxylamine derivative of procainamide (procainamide hydroxylamine [PAHA]). The objective of this study was to examine the effects of PAHA on human lymphocytes and adherent cells (monocytes and macrophages). When incubated with lymphocytes in whole blood, PAHA enhanced the response to mitogen and immunoglobulin secretion at lower concentrations (less than or equal to 4 mumol/L) but suppressed these functions at higher concentrations. The cytotoxic effects were nonselective for T lymphocytes and B lymphocytes and appeared to involve an interaction between PAHA and hemoglobin. When erythrocytes were removed or when hemoglobin was converted to carboxyhemoglobin, the suppressive effects of PAHA on lymphocytes were reduced. PAHA stimulated interleukin-1 production by adherent cells at 25 mumol/L but had no effect at lower concentrations. Superoxide anion release was unaffected by PAHA in "resting" adherent cells. Pretreatment with PAHA (2 mumol/L) diminished superoxide release in response to stimulation by phorbol myristate acetate (PMA) or latex bead phagocytosis but augmented superoxide release when coincubated with PMA or latex. These observations indicate that PAHA produces complex, concentration-dependent interactions with human immunoregulatory cells, and they suggest that the effects of PAHA on lymphocyte function may result from the further oxidation of PAHA by hemoglobin, perhaps to the nitroso form.