Murine lupus susceptibility locus Sle1a requires the expression of two sub-loci to induce inflammatory T cells.

The NZM2410-derived Sle1a lupus susceptibility locus induces activated autoreactive CD4(+) T cells and reduces the number and function of Foxp3(+) regulatory T cells (Tregs). In this study, we first showed that Sle1a contributes to autoimmunity by increasing antinuclear antibody production when expressed on either NZB or NZW heterozygous genomes, and by enhancing the chronic graft versus host disease response indicating an expansion of the autoreactive B-cell pool. Screening two non-overlapping recombinants, the Sle1a.1 and Sle1a.2 intervals that cover the entire Sle1a locus, revealed that both Sle1a.1 and Sle1a.2 were necessary for the full Sle1a phenotype. Sle1a.1, and to a lesser extent Sle1a.2, significantly affected CD4(+) T-cell activation as well as Treg differentiation and function. Sle1a.2 also increased the production of autoreactive B cells. As the Sle1a.1 and Sle1a.2 intervals contain only 1 and 15 known genes, respectively, this study considerably reduces the number of candidate genes responsible for the production of autoreactive T cells. These results also show that the Sle1 locus is an excellent model for the genetic architecture of lupus, in which a major obligate phenotype results from the coexpression of multiple genetic variants with individual weak effects.

CD4(+) T cells from lupus-prone mice are hyperresponsive to T cell receptor engagement with low and high affinity peptide antigens: a model to explain spontaneous T cell activation in lupus.

Polyclonal CD4(+) T cell activation is characteristic of spontaneous lupus. As a potential explanation for this phenotype, we hypothesized that T cells from lupus-prone mice are intrinsically hyperresponsive to stimulation with antigen, particularly to those peptide ligands having a low affinity for the T cell receptor (TCR). To test this hypothesis, we backcrossed the alpha and beta chain genes of the AND TCR specific for amino acids 88-104 of pigeon cytochrome C (PCC) to the Fas-intact MRL/Mp(+)(Fas-lpr) and to the H-2(k)-matched control backgrounds B10.BR and CBA/CaJ (MRL.AND, B10.AND, and CBA.AND, respectively), and assessed naive CD4(+) TCR transgenic T cell activation in vitro after its encounter with cognate antigen and lower affinity altered peptide ligands (APLs). MRL.AND T cells, compared with control B10.AND and CBA.AND cells, proliferated more when stimulated with agonist antigen. More strikingly, MRL.AND T cells proliferated significantly more and produced more interleukin 2 when stimulated with the APLs of PCC 88-104, having lower affinity for the transgenic TCR. These results imply that one of the forces driving polyclonal activation of alpha/beta T cells in lupus is an intrinsically heightened response to peptide antigen, particularly those with low affinity for the TCR, independent of the nature of the antigen-presenting cell and degree of costimulation.

(SWR x SJL)F1 mice: a new model of lupus-like disease.

During the study of autoimmune models we found that (SWR x SJL)F1 mice (both parental strains with the V beta a phenotype) spontaneously produced immunoglobulin G (IgG) antibodies directed against Sm/U1 small nuclear ribonucleoproteins (snRNPs). In some of these females, the presence of these autoantibodies was found as early as 10 wk of age. Their frequency increased with age i.e., 70% at 40 wk. At that time, only 10% of males developed anti-Sm/U1snRNP antibodies. Anti-Sm/U1snRNP antibodies from positive mice generally recognized the peptides BB', D, 70 kD, and A from RNPs. These polypeptides are known to bear the autoantigenic epitopes that are recognized by human sera containing anti-Sm and anti-U1snRNP antibodies. Reactivity of IgG antibodies with the octapeptide sequence PPPGMRPP was also found in 30% of anti-Sm/U1snRNP positive (SWR x SJL)F1 mice that precipitated BB' peptides. This octapeptide has been described as the most immunoreactive linear epitope in systemic lupus erythematosus (SLE) patients with anti-Sm and anti-U1snRNP antibodies. Approximately 30% of anti-Sn/U1snRNP positive females, later produced anti-dsDNA antibodies. This fact was accompanied by the development of proteinuria due to glomerulonephritis mediated by immunocomplexes. In addition to the specific autoimmune response, (SWR x SJL)F1 females also showed other immunologic abnormalities such as hypergammaglobulinemia, and an approximately twofold increase in spleen cell number compared with control mice. These results indicate that (SWR x SJL)F1 females develop clinical and serological abnormalities similar to those observed in human SLE and constitute a novel model for the study of the genetic mechanisms that result in autoimmunity.

SH2D1A regulates T-dependent humoral autoimmunity.

The signaling lymphocytic activation molecule (SLAM)/CD150 family includes a family of chromosome 1-encoded cell surface molecules with costimulatory functions mediated in part by the adaptor protein SH2D1A (SLAM-associated protein, SAP). Deficiency in SH2D1A protects mice from an experimental model of lupus, including the development of hypergammaglobulinemia, autoantibodies including anti-double stranded DNA, and renal disease. This protection did not reflect grossly defective T or B cell function per se because SH2D1A-deficient mice were susceptible to experimental autoimmune encephalomyelitis, a T cell-dependent disease, and they were capable of mounting normal T-independent antigen-specific immunoglobulin responses. Instead, T-dependent antibody responses were impaired in SH2D1A-deficient mice, reflecting defective germinal center formation. These findings demonstrate a specific role for the SLAM-SH2D1A system in the regulation of T-dependent humoral immune responses, implicating members of the CD150-SH2D1A family as targets in the pathogenesis and therapy of antibody-mediated autoimmune and allergic diseases.

Promiscuous presentation and recognition of nucleosomal autoepitopes in lupus: role of autoimmune T cell receptor alpha chain.

T cells specific for nucleosomal autoepitopes are selectively expanded in lupus mice and these Th cells drive autoimmune B cells to produce pathogenic antinuclear antibodies. We transfected the TCR-alpha and -beta chain genes of a representative, pathogenic autoantibody-inducing Th clone specific for the nucleosomal core histone peptide H471-94 into TCR-negative recipient cells. Although the autoimmune TCRs were originally derived from SNF1 (I-Ad/q) mice, the transfectants could recognize the nucleosomal autoepitope presented by APC-bearing I-A molecules of all haplotypes tested, as well as human DR molecules. Competition assays indicated that the autoepitopes bound to the MHC class II groove. Most remarkably, MHC-unrestricted recognition of the nucleosomal peptide epitope was conferred by the lupus TCR-alpha chain even when it paired with a TCR-beta chain of irrelevant specificity. Several other disease-relevant Th clones and splenic T cells of lupus mice had similar properties. The TCR-alpha chains of these murine lupus Th clones shared related motifs and charged residues in their CDRs, and similar motifs were apparent even in TCR-alpha chains of human lupus Th clones. The lupus TCR-alpha chains probably contact the nucleosomal peptide complexed with MHC with relatively high affinity/avidity to sustain TCR signaling, because CD4 coreceptor was not required for promiscuous recognition. Indeed, pathogenic autoantibody-inducing, CD4-negative, TCR-alphabeta+ Th cells are expanded in systemic lupus erythematosus. These results have implications regarding thymic selection and peripheral expansion of nucleosome-specific T cells in lupus. They also suggest that universally tolerogenic epitopes could be designed for therapy of lupus patients with diverse HLA alleles. We propose to designate nucleosomes and other antigens bearing universal epitopes "Pantigens" (for promiscuous antigens).

A novel mouse with B cells but lacking serum antibody reveals an antibody-independent role for B cells in murine lupus.

The precise role of B cells in systemic autoimmunity is incompletely understood. Although B cells are necessary for expression of disease (Chan, O., and M.J. Shlomchik. 1998. J. Immunol. 160:51-59, and Shlomchik, M.J., M.P. Madaio, D. Ni, M. Trounstine, and D. Huszar. 1994. J. Exp. Med. 180:1295-1306), it is unclear whether autoantibody production, antigen presentation, and/or other B cell functions are required for the complete pathologic phenotype. To address this issue, two experimental approaches were used. In the first, the individual contributions of circulating antibodies and B cells were analyzed using MRL/MpJ-Faslpr (MRL/lpr) mice that expressed a mutant transgene encoding surface immunoglobulin (Ig), but which did not permit the secretion of circulating Ig. These mice developed nephritis, characterized by cellular infiltration within the kidney, indicating that B cells themselves, without soluble autoantibody production, exert a pathogenic role. The results indicate that, independent of serum autoantibody, functional B cells expressing surface Ig are essential for disease expression, either by serving as antigen-presenting cells for antigen-specific, autoreactive T cells, or by contributing directly to local inflammation.

Autoimmune-mediated congenital heart block.

Autoimmune-mediated congenital heart block (CHB) is a severe manifestation of neonatal lupus in which conduction tissues of the fetal heart are damaged. This occurs due to passive transference of maternal anti-SSA/Ro and anti-SSB/La autoantibodies and subsequent inflammation and fibrosis of the atrioventricular (AV) node. Notably, the disease manifests after the fetal heart has structurally developed, ruling out other anatomical abnormalities that could otherwise contribute to the block of conduction. Complete AV block is irreversible and the most common manifestation of CHB, although other cardiac complications such as endocardial fibroelastosis (EFE), dilated cardiomyopathy, and valvular insufficiency have been observed. In this review, we detail the classification, prevalence, pathogenesis, and clinical management recommendations for autoimmune CHB.

Antibodies against citrullinated proteins enhance tissue injury in experimental autoimmune arthritis.

Antibodies against citrullinated proteins are specific and predictive markers for rheumatoid arthritis although the pathologic relevance of these antibodies remains unclear. To investigate the significance of these autoantibodies, collagen-induced arthritis (CIA) in mice was used to establish an animal model of antibody reactivity to citrullinated proteins. DBA/1J mice were immunized with bovine type II collagen (CII) at days 0 and 21, and serum was collected every 7 days for analysis. Antibodies against both CII and cyclic citrullinated peptide, one such citrullinated antigen, appeared early after immunization, before joint swelling was observed. Further, these antibodies demonstrated specific binding to citrullinated filaggrin in rat esophagus by indirect immunofluorescence and citrullinated fibrinogen by Western blot. To evaluate the role of immune responses to citrullinated proteins in CIA, mice were tolerized with a citrulline-containing peptide, followed by antigen challenge with CII. Tolerized mice demonstrated significantly reduced disease severity and incidence compared with controls. We also identified novel murine monoclonal antibodies specific to citrullinated fibrinogen that enhanced arthritis when coadministered with a submaximal dose of anti-CII antibodies and bound targets within the inflamed synovium of mice with CIA. These results demonstrate that antibodies against citrullinated proteins are centrally involved in the pathogenesis of autoimmune arthritis.

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.

Mechanisms of drug-induced lupus. II. T cells overexpressing lymphocyte function-associated antigen 1 become autoreactive and cause a lupuslike disease in syngeneic mice.

Current theories propose that systemic lupus erythematosus develops when genetically predisposed individuals are exposed to certain environmental agents, although how these agents trigger lupus is uncertain. Some of these agents, such as procainamide, hydralazine, and UV-light inhibit T cell DNA methylation, increase lymphocyte function-associated antigen 1 (LFA-1) (CD11a/CD18) expression, and induce autoreactivity in vitro, and adoptive transfer of T cells that are made autoreactive by this mechanism causes a lupuslike disease. The mechanism by which these cells cause autoimmunity is unknown. In this report, we present evidence that LFA-1 overexpression is sufficient to induce autoimmunity. LFA-1 overexpression was induced on cloned murine Th2 cells by transfection, resulting in autoreactivity. Adoptive transfer of the transfected, autoreactive cells into syngeneic recipients caused a lupuslike disease with anti-DNA antibodies, an immune complex glomerulonephritis and pulmonary alveolitis, similar to that caused by cells treated with procainamide. These results indicate that agents or events which modify T cell DNA methylation may induce autoimmunity by causing T cell LFA-1 overexpression. Since T cells from patients with active lupus have hypomethylated DNA and overexpressed LFA-1, this mechanism could be important in the development of human autoimmunity.

Interferon-gamma is required for lupus-like disease and lymphoaccumulation in MRL-lpr mice.

Congenic MRL-lpr mice homozygous and heterozygous for the IFN-gamma gene disruption were created to assess the role of this pleotropic cytokine on the lymphoaccumulation and lupus-like disease of Fas-defective mice. Early death was prevented, and glomerulonephritis severely reduced in IFN-gamma-/- mice. Hypergammaglobulinemia was maintained with a switch from IgG2a to IgG1 predominance, but the dramatic decrease in levels of the dominant IgG2a anti-dsDNA autoantibodies was not associated with a compensatory increase in TH2-associated IgG subclasses. Remarkably, early death and glomerulonephritis were also prevented in IFN-gamma+/- mice, although autoantibody levels and glomerular immune deposits were equivalent to IFN-gamma+/+ lpr mice, indicating the importance of additional locally-exerted disease-promoting effects of IFN-gamma. IFN-gamma-/- mice exhibited reduced lymphadenopathy concomitant to a decrease in DN B220(+) T cells. In vivo BrdU labeling showed reduced proliferation of DN B220(+) cells in IFN-gamma-/- vs. IFN-gamma+/+ lpr mice, while enhanced proliferation of all other T cell subsets was unaffected. Macrophages of IFN-gamma-/-lpr mice expressed markedly decreased levels of MHC class I and II molecules compared with controls. Moreover, the heightened expression of MHC class II molecules on proximal tubules of IFN-gamma+/+ lpr mice was significantly reduced in both IFN-gamma-/- and IFN-gamma+/- mice. The data indicate that IFN-gamma hyperproduction is required for lupus development, presumably by increasing MHC expression and autoantigen presentation to otherwise quiescent nontolerant anti-self T cells, and also by promoting local immune and inflammatory processes.

Activation of natural killer T cells in NZB/W mice induces Th1-type immune responses exacerbating lupus.

In vivo treatment of mice with the natural killer T (NKT) cell ligand, alpha-galactosylceramide (alphaGalCer), ameliorates autoimmune diabetes and experimental autoimmune encephalomyelitis (EAE) by shifting pathogenic Th1-type immune responses to nonpathogenic Th2-type responses. In the current study, in vivo activation of NKT cells in adult NZB/W mice by multiple injections of alphaGalCer induced an abnormal Th1-type immune response as compared with the Th2-type response observed in nonautoimmune C57BL/6 mice. This resulted in decreased serum levels of IgE, increased levels of IgG2a and IgG2a anti-double-stranded DNA (anti-dsDNA) Ab's, and exacerbated lupus. Conversely, treatment of NZB/W mice with blocking anti-CD1d mAb augmented Th2-type responses, increased serum levels of IgE, decreased levels of IgG2a and IgG2a anti-dsDNA Ab's, and ameliorated lupus. While total CD4+ T cells markedly augmented in vitro IgM anti-dsDNA Ab secretion by splenic B cells, the non-CD1d-reactive (CD1d-alphaGalCer tetramer-negative) CD4+ T cells (accounting for 95% of all CD4+ T cells) failed to augment Ab secretion. The CD1d-reactive tetramer-positive CD4+ T cells augmented anti-dsDNA Ab secretion about tenfold. In conclusion, activation of NKT cells augments Th1-type immune responses and autoantibody secretion that contribute to lupus development in adult NZB/W mice, and anti-CD1d mAb might be useful for treating lupus.

Drug-induced anti-histone autoantibodies display two patterns of reactivity with substructures of chromatin.

Increasing evidence suggests that autoantibodies in the rheumatic diseases are a consequence of immune selection by self-material, but the nature of the in vivo immunogen is unknown. Insight into this problem may be obtained by measuring autoantibody binding to various forms of a target antigen. Antihistone antibodies arising as a side effect of therapy with various drugs offer an opportunity to explore this premise because many forms of histone have been characterized and adapted to ELISA formats. Two patterns of antibody reactivity were observed. All 21 patients with symptomatic procainamide-induced lupus and 7 of 12 patients with quinidine-induced lupus had IgG antibodies reacting predominantly with the (H2A-H2B)-DNA complex and with chromatin. In contrast, antibodies in 19 of 24 patients taking procainamide without accompanying lupus-like symptoms did not show any pattern. The second pattern was observed in 18/19 chlorpromazine-treated patients and 14/17 patients with hydralazine-induced lupus in which IgM antibodies displayed more reactivity with DNA-free histones than with the corresponding histone-DNA complexes and almost no binding to H1-stripped chromatin. Absorption studies were entirely consistent with these results. Thus, the two patterns of reactivity with nucleosomal components reflect the molecular substructure of chromatin, suggesting that two processes underlie antihistone antibody induction by drugs. In one, IgG autoantibodies appear to be elicited by chromatin, whereas in the other, autoimmune tolerance to native chromatin appears largely intact, and IgM antibodies may be driven by DNA-free histone.

Genesis and evolution of antichromatin autoantibodies in murine lupus implicates T-dependent immunization with self antigen.

Autoantibodies reacting with chromatin and its components, histones and DNA, are characteristic of the human autoimmune disease SLE and drug-induced lupus, but the mechanisms of their induction remain unknown. Serial serum samples collected over short intervals from lupus-prone MRL/MP-lpr/lpr and BXSB mice were tested by ELISA on chromatin and its substructures to characterize the initial autoimmune response to these antigens. Direct binding studies demonstrated that the early autoantibodies recognized discontinuous epitopes on native chromatin and the (H2A-H2B)-DNA subnucleosome. As the immune response progressed, native DNA and other chromatin constituents generally became antigenic. Based on adsorption studies and IgG subclass restriction, antibodies to native DNA were more related to chromatin than to denatured DNA. The kinetics of autoantibody appearance and the Ig class distribution were similar to the kinetics and distribution seen in antibodies induced by immunization with an exogenous T-dependent antigen. These results are most consistent with the view that autoantibodies reacting with chromatin are generated by autoimmunization with chromatin, and antibodies to native DNA are a subset of the wide spectrum of antichromatin autoantibodies.

Studies with human leukocyte lysosomes. Evidence for antilysosome antibodies in lupus erythematosus and for the presence of lysosomal antigen in inflammatory diseases.

Human lysosomes were isolated from normal peripheral blood leukoyctes and characterized by electron microscopy, enzyme analysis, and assays for DNA and RNA. Stored sera from 37 unselected patients with systemic lupus erythematosus (SLE), including active and inactive, treated and untreated cases, were tested in complement fixation (CF) reactions with these lysosome preparations. 23 SLE sera exhibited positive CR reactions, as did sera from two patients with "lupoid" hepatitis. The seven SLE sera with strongest CF reactivity also demonstrated gel precipitin reactions with lysosomes. Neither CF nor precipitin reactions with lysosomes were observed with normal sera or with sera of patients with drug-induced lupus syndrome, rheumatoid arthritis (RA), polymyositis, or autoimmune hemolytic anemia. By several criteria the antilysosome CF and precipitin reactions of SLE sera cound not be attributed to antibody to DNA, RNA, or other intracellular organelles. The lysosomal component reactive with SLE sera in CF assays was sedimentable at high speed and is presumably membrane associated. The CF activity of two representative SLE sera was associated with IgG globulins by Sephadex filtration. A search for lysosomal antigen in SLE and related disorders was also made. By employing rabbit antiserum to human lysosomes in immunodiffusion, a soluble lysosomal component, apparently distinct from the sedimentable (membrane-associated) antigen described above, was identified in serum, synovial fluid, or pleural fluid from patients with SLE, RA, ankylosing spondylitis, and leukemoid reaction. An antigenically identical soluble component reactive with the rabbit antiserum could be released in vitro from intact lysosomes by repeated freeze-thaw cycles..

Antibody induction of lupus-like neuropsychiatric manifestations.

Although systemic lupus erythematosus (SLE) is usually evaluated with regard to autoimmune reactivity toward the kidney, there are multiple psychiatric abnormalities associated with this autoimmune disease. Lupus-prone male NZM88 mice, derived from NZB/NZW F1 mice, develop early neuropsychiatric manifestations without any signs of nephritis. In addition to the usual repertoire of antibody specificities, including autoantibodies to dsDNA and renal antigens, mice of this inbred strain express autoantibodies to numerous brain antigens. Here, we show that autoantibodies to brain antigens, assessed by Western analysis, are as individually varied as are the diverse neuropsychiatric manifestations observed in SLE patients. Additionally, a monoclonal antibody derived from the spleen of an untreated NZM88 male when injected into healthy BALB/cByJ, but not C57BL/6J, mice induced behaviors similar to those of lupus-prone NZM88 mice. This monoclonal antibody, which is specific to dynamin-1, binds preferentially in BALB/cByJ cortex and induces substantial expression of cytokines mainly in the hypothalamus. Thus, an antibody to just one brain antigen can induce multiple behavioral changes, and multiple autoantibodies to different brain antigens exist in lupus-prone mice; however, susceptibility to the induction of neurobehavioral deficits is dependent on host genetics.

Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells.

Small ribonucleic acid (RNA)-protein complexes precipitated by anti-Ro and anti-La antibodies from lupus patients have been examined with emphasis on their RNA components. In both ribonucleoprotein (RNP) classes, the numbers of different RNA molecules and their sequences vary between mouse and human cells. The complex mixtures of La RNAs include two previously sequenced 4.5S RNAs from mouse cells and 5S ribosomal RNA-like molecules from both mouse and human cells. All Ro and La RNAs possess 5-triphosphates. Some La RNAs have internal modifications typical of transfer RNAs. The Ro RNPs are quite stable and are localized by immunofluorescence in the cell cytoplasm, whereas the majority of the La RNPs turn over rapidly and reside in the nucleus. Despite these differences, reconstitution experiments show that the Ro particles carry the La as well as the Ro determinant. Studies using a nuclear transcription system demonstrate that most of the La RNAs are synthesized by RNA polymerase III. The possibility that the La protein(s) functions in the transcription or maturation of all RNA polymerase III transcripts is discussed.

Recurrent congenital heart block in neonatal lupus.

Congenital heart block (CHB) is the main complication of neonatal lupus (NL) and is strongly associated with the presence of anti-SSA/Ro and anti-SSB/La antibodies. The recurrence of CHB in subsequent pregnancies in mothers with these antibodies is uncommon, occurring in approximately 15% of cases. We describe here a case of recurrent CHB in a previously asymptomatic mother with Sjögren syndrome and discuss the current strategies for the prevention and treatment of CHB in NL.

Induction of lupus-related specific autoantibodies by non-specific inflammation caused by an intraperitoneal injection of n-hexadecane in BALB/c mice.

A single intraperitoneal (i.p.) injection of pristane, incomplete Freund's adjuvant (IFA), or the adjuvant oil squalene, but not high molecular weight medicinal mineral oils, induces lupus-related autoantibodies to nRNP/Sm and -Su in non-autoimmune strains of mice. This ability appears to be associated with the low molecular weight and adjuvanticity of hydrocarbon. n-Hexadecane (C(16)H(34)), which is present in petroleum, has adjuvant activity and induces arthritis in rodents like other lupus-inducing oils. In addition to dietary exposure to n-hexadecane in mineral oils, exposure also occurs via inhalation of oil mist, jet fuel, or diesel exhaust or by absorption through the skin. Since n-hexadecane is a low molecular weight adjuvant hydrocarbon oil similar to other lupus-inducing hydrocarbons, the present study examined whether it can also induce lupus-related autoantibodies in mice. Female BALB/cJ mice received a single i.p. injection of 0.5 ml of n-hexadecane, pristane, or saline (control). Pathology and serology (immunoglobulin levels, autoantibodies by immunofluorescence, immunoprecipitation, and ELISA) were examined 3 months later. Unexpectedly, all n-hexadecane-treated mice, but none in the other groups, developed inflammatory ascites within 2.5 months. n-Hexadecane induced hypergammaglobulinemia (IgG1, IgG2a), antinuclear (titer>1:160, 67%) and -cytoplasmic antibodies (58%) and autoantibodies to nRNP/Sm (25%), Su (33%), ssDNA (83%), and chromatin (100%). Therefore, non-specific inflammation caused by n-hexadecane resulted in the production of a limited set of specific autoantibodies. These previously unrecognized immunological effects of n-hexadecane may have implications in monitoring human exposure to hydrocarbons and in the pathogenesis of autoimmune diseases.