Immunization of naive BALB/c mice with human beta2-glycoprotein I breaks tolerance to the murine molecule

Antiphospholipid syndrome pathogenesis in 2023: an update of new mechanisms or just a reconsideration of the old ones?

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (β2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). β2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating β2GPI tissue presentation. β2GPI/β2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

Oral administration of Domain-I of beta-2glycoprotein-I induces immunological tolerance in experimental murine antiphospholipid syndrome

It is well established that the humoral immunity in antiphospholipid syndrome (APS) is presented by circulating pathogenic anti-β2GPI autoantibodies targeting mainly domain I of the β2GPI protein, playing a major role in the disease pathogenesis. Previously, we have demonstrated that treatment of experimental APS mice with tolerogenic dendritic cells loaded with domain-I was more efficient in tolerance induction than with the whole molecule or domain-V. In the current study we had orally administered a domain-I derivative of the β2GPI molecule, as a new therapeutic approach to induce oral tolerance in this mouse model of APS. BALB/c mice immunized with β2GPI, were fed with either domain-I, domain-V derivative or the complete β2GPI protein. β2GPI immunized mice developed experimental APS which were fed with domain-I significantly had decreased fetal loss (p < 0.004), a lower size of thrombi (p < 0.001) and lower circulating anti-β2GPI Abs in comparison to mice fed with domain-V or PBS (p < 0.002). Likewise, Domain-I fed mice had a lowered inflammatory response, exhibited by decreased expression of inflammatory cytokines (IFNγ, IL-6, IL-17) and elevated production of IL-10 anti-inflammatory cytokine by splenocytes. Moreover, the anti-inflammatory response in the domain-I fed APS mice was associated with increased circulating miRNA variations (155, 146, 182, 98) by RT-PCR, which are associated with immunomodulation of the immune network. We propose that oral tolerance with domain-I can be a novel therapy for patients with APS.

Major Histocompatibility Complex Class II Alleles Influence Induction of Pathogenic Antiphospholipid Antibodies in a Mouse Model of Thrombosis

OBJECTIVE

Both environmental and genetic factors are important in the development of antiphospholipid antibodies (aPL) in patients with antiphospholipid syndrome (APS). Currently, the only available data on predisposing genetic factors have been obtained from epidemiologic studies, without mechanistic evidence. Therefore, we studied the influence of major histocompatibility complex (MHC) class II alleles on the production of aPL in a mouse model of APS.

METHODS

Three groups of mice, MHC class II-deficient (MHCII^-/- ) mice, MHCII^-/- mice transgenic for human HLA-DQ6 (DQ6), DQ8, or DR4 alleles, and the corresponding wild-type (WT) mouse strains were immunized; half were immunized with human β₂ -glycoprotein I (β₂ GPI), and the other half were immunized with control ovalbumin (OVA) protein. Thrombus formation in vivo, tissue factor activity in carotid and peritoneal macrophages, and serum levels of tumor necrosis factor (TNF), IgG anticardiolipin (aCL), antibodies, and anti-OVA antibodies were determined.

RESULTS

Immunization with β₂ GPI induced significant production of aCL and anti-β₂ GPI in WT mice compared with control mice immunized with OVA (P < 0.001) but diminished aCL (P < 0.001) and anti-β₂ GPI (P = 0.016) production in MHCII^-/- mice. Anti-β₂ GPI production was fully restored in DQ6 and DQ8 mice, while levels of anti-β₂ GPI in DR4 mice and aCL in all transgenic lines were only partially restored (P < 0.001 to P < 0.046). Thrombus size in WT mice was twice that in MHCII^-/- mice (P < 0.001) but similar to that in all transgenic lines. Carotid and peritoneal macrophage tissue factor levels decreased by >50% in MHCII^-/- mice compared with wild-type B6 mice and were restored in DQ8 mice but not DR4 mice or DQ6 mice. TNF levels decreased 4-fold in MHCII^-/- mice (P < 0.001) and were not restored in transgenic mice.

CONCLUSION

Our mechanistic study is the first to show that MHC class II alleles influence not only quantitative aPL production but also the pathogenic capacity of induced aPL.

Review on Toll-Like Receptor Activation in Myasthenia Gravis: Application to the Development of New Experimental Models

Abnormal toll-like receptor (TLR) activation and uncontrolled resolution of inflammation are suspected to play a key role in the development of autoimmune diseases. Acquired myasthenia gravis (MG) is an invalidating neuromuscular disease leading to muscle weaknesses. MG is mainly mediated by anti-acetylcholine receptor (AChR) autoantibodies, and thymic hyperplasia characterized by ectopic germinal centers is a common feature in MG. An abnormal expression of certain TLRs is observed in the thymus of MG patients associated with the overexpression of interferon (IFN)-β, the orchestrator of thymic changes in MG. Experimental models have been developed for numerous autoimmune diseases. These models are induced by animal immunization with a purified antigen solubilized in complete Freund's adjuvant (CFA) containing heat-inactivated mycobacterium tuberculosis (MTB). Sensitization against the antigen is mainly due to the activation of TLR signaling pathways by the pathogen motifs displayed by MTB, and attempts have been made to substitute the use of CFA by TLR agonists. AChR emulsified in CFA is used to induce the classical experimental autoimmune MG model (EAMG). However, the TLR4 activator lipopolysaccharide (LPS) has proved to be efficient to replace MTB and induce a sensitization against purified AChR. Poly(I:C), the well-known TLR3 agonist, is also able by itself to induce MG symptoms in mice associated with early thymic changes as observed in human MG. In this review, we discuss the abnormal expression of TLRs in MG patients and we describe the use of TLR agonists to induce EAMG in comparison with other autoimmune experimental models.

Study on the pathogenesis of autoimmune-type recurrent spontaneous abortion by establishing a new mouse model

OBJECTIVE

To establish a new mouse model for autoimmune-type recurrent spontaneous abortion (AI-RSA) and demonstrate the potential role of intrauterine immunization with β2GP-1-like antigen in AI-RSA, we performed an intrauterine injection of human β2GP-1 in BALB/c mice and unrelated protein, adjuvants, and normal saline (NS) as controls. The mean number of embryos implanted (MNEI), embryo loss rate (ELR), mean embryo bulk (MEB), and mean placental weight (MPW) were analyzed. Compared with the control mice, BALB/c mice injected with human β2GP-1 showed increased anti-β2GP-1 and MPW. Moreover, BALB/c mice immunized with human β2GP-1 exhibited hypercoagulability and vascular thrombus formation in the placenta. Electron microscopy confirmed the existence of platelet aggregation, mitochondrial swelling, and endothelial cell necrosis in the placentas of BALB/c mice immunized with human β2GP-1. These finding indicated that intrauterine immunization with β2GP-1 successfully induced AI-RSA in mice. Increased anti-β2GP-1 antibody could independently induce hypercoagulability, vascular endothelial injury, and vascular thrombus formation in the placenta, which led to AI-RSA.

[Efficacy and safety of rituximab in the treatment of primary antiphospholipid syndrome: analysis of 24 cases from the bibliography review]

BACKGROUND AND OBJECTIVE

Antiphospholipid syndrome (APS) is characterized by the presence of antiphospholipid antibodies (aPL) and thrombotic and/or obstetric manifestations. Patients without another associated autoimmune disease are considered to have primary APS. Some patients develop thrombosis recurrence despite anticoagulant treatment and some clinical features do not respond to standard therapy. Rituximab may be an alternative in these cases. We review the published scientific evidence on the use of rituximab in the treatment of primary APS.

PATIENTS AND METHODS

Description of a case and review of the literature with descriptive analysis of the demographic, clinical, and immunologic features, treatment and outcome of patients.

RESULTS

We identified 24 patients (15 women [62.5%]), with a mean age of 37.0 ± 13.4 years. The reasons for the use of rituximab were thrombocytopenia (41.7%), skin involvement (33.3%), neurologic and heart valve involvement (12.5%), hemolytic anemia (8.3%) and pulmonary and renal involvement (4.2%). Lupus anticoagulant was present in 72.7% of the cases, the IgG and IgM isotypes of anticardiolipin antibodies in 75 and 50%, respectively, and the anti-β2GPI (IgG e IgM) antibodies in 80% of patients. Thirteen (54.1%) patients received 2 doses of 1,000 mg of rituximab fortnightly, 10 (41.7%) 4 doses of 375 mg/m(2) weekly and one (4.2%) 8 doses of 375 mg/m(2) weekly. Eleven (45.8%) patients presented a complete clinical response, 7 (29.2%) a partial response and 6 (25%) did not respond to rituximab. Four patients with clinical improvement presented with aPL titer decrease and in one patient, aPL levels did not change. In one patient without clinical response, aPL remained positive. A clinical-immunologic dissociation existed in 2 additional cases.

CONCLUSIONS

The results obtained suggest a possible potential benefit of rituximab in the treatment of some clinical manifestations of primary APS such as thrombocytopenia, skin and heart valve involvement.

C6 knock-out mice are protected from thrombophilia mediated by antiphospholipid antibodies

BACKGROUND

Complement activation plays a role in pathogenesis of the antiphospholipid syndrome (APS), but the involvement of the C5b-9 membrane attack complex (MAC) is unknown. Here we studied the effects of human polyclonal antiphospholipid (aPL) antibodies on thrombosis and tissue factor (TF) up-regulation in C6 deficient (C6(-/-)) mice.

METHODS

C6(-/-) mice or the wild-type C3H/HeJ (C6(+/+)) mice were injected twice with IgG-APS (n = 2) or IgM-APS (n = 1) isolated from APS patients or with the corresponding control immunoglobulins (Igs) of normal human serum, (NHS) (IgG-NHS or IgM-NHS). Then, the sizes of induced thrombi in the femoral vein were determined 72 hours after the first injection. Tissue factor was determined in homogenates of carotid arteries and in peritoneal macrophages.

RESULTS

Thrombus sizes were significantly larger in C6(+/+) treated with IgG-APS1 or with IgG-APS2 or with IgM-APS when compared with C6(+/+) mice treated with IgG-NHS or with IgM-NHS, respectively. The sizes of thrombi were significantly smaller in the C6(-/-) mice injected with IgG-APS1, IgG-APS2 or IgM-APS (p < 0.001), compared to their C6(+/+) counterparts showing an important abrogation of thrombus formation in mice lacking C6. The TF expression and activity in the C6(-/-) mice treated with IgG-APS or IgM-APS were diminished when compared to C3H/HeJ (C6(+/+)) mice treated with the same Igs. All mice injected with IgG-APS and IgM-APS had medium-high titers of anticardiolipin (aCL) and anti-β(2)glycoprotein I (aβ(2)GPI) antibodies.

CONCLUSIONS

These data indicate that the C6 component of the complement system mediates aPL-thrombogenic effects, underscoring an important pathogenic mechanism and indicating the possibility of inhibiting complement to ameliorate APS-related manifestations.

β₂-Glycoprotein-1 autoantibodies from patients with antiphospholipid syndrome are sufficient to potentiate arterial thrombus formation in a mouse model

Antiphospholipid syndrome is characterized by thrombosis, recurrent fetal loss, and the presence of the lupus anticoagulant, anticardiolipin antibodies, or anti-β(2)-glycoprotein-1 (anti-β(2)-GP1) antibodies. Although anti-β(2)-GP1 antibodies have been documented as a biomarker for diagnosis of antiphospholipid syndrome, their direct role in the pathogenesis of thrombosis is unknown. We have demonstrated using intravital microscopy that anti-β(2)-GP1 autoantibodies purified from the sera of patients with antiphospholipid syndrome complicated by thrombosis greatly amplify thrombus size after laser-induced vessel wall injury in live mice. Anti-β(2)-GP1 autoantibodies from 3 patients with antiphospholipid syndrome were affinity-purified using human β(2)-GP1 bound to agarose. The effects of purified anti-β(2)-GP1 IgG autoantibodies, of anti-β(2)-GP1-depleted IgG, and of IgG from normal human sera on thrombus formation were measured in mice after arterial injury in the cremaster muscle. Before injury, purified anti-β(2)-GP1 IgG autoantibodies, anti-β(2)-GP1 antibody-depleted IgG, or IgG from normal human sera were infused. Increasing amounts of purified anti-β(2)-GP1 autoantibodies increased thrombus size in a dose-dependent manner, whereas neither anti-β(2)-GP1 antibody-depleted IgG nor IgG from normal serum affected thrombus size. These results indicate that anti-β(2)-GP1 IgG autoantibodies in antiphospholipid syndrome patient sera are not only a marker of antiphospholipid syndrome but are directly involved in the pathogenesis of thrombosis.

Pathogenesis of the antiphospholipid syndrome: an additional example of the mosaic of autoimmunity

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by an adaptive immune response against self-PL-binding proteins ending in the production of specific autoantibodies. Antiphospholipid antibodies (aPL; and in particular anti-beta2 glycoprotein I antibodies) are formal diagnostic markers and pathogenic antibodies. Although APS may be considered as an autoantibody-mediated disease, there is now evidence that aPL are necessary but not sufficient to trigger some of the clinical manifestations of the syndrome. For example, additional factors, such as mediators of the innate immunity are now recognized to play a key role as second hits able to induce the thrombotic events in the presence of the autoantibodies. The APS scenario is also supplemented by the influence of genetically determined factors. Finally, environmental agents - in particular infectious ones - were reported to act as triggers for the production of autoantibodies cross-reacting with PL-binding proteins as well as inflammatory stimuli that potentiate the aPL thrombogenic effect. Altogether these findings do support the concept of a mosaic of factors that participate to the pathogenesis of the syndrome at different levels.

Requirement for dendritic cells in the establishment of anti-phospholipid antibodies

OBJECTIVE

The cross-presentation of cell-associated autoantigens contributes to systemic autoimmune diseases, including systemic lupus erythematosus (SLE). Little is known about the regulation of the immune response against soluble autoantigens targeted in these diseases.

METHODS

We immunized the offspring of New Zealand Black and New Zealand White mice (NZB x NZW F(1)) with syngeneic dendritic cells (DC) that had macropinocytosed beta2-glycoprotein 1 (beta(2)GPI) during propagation in normal mouse serum or that had phagocytosed apoptotic thymocytes with syngeneic (murine) or xenogeneic (bovine) beta(2)GPI, which was associated to plasma membrane of the cells. Mice were in parallel immunized with apoptotic thymocytes that had associated the beta(2)GPI to their membranes in the absence of DC. The development of anti-beta(2)GPI antibodies and clinical features were monitored.

RESULTS

Apoptotic cells alone, opsonized with beta(2)GPI, failed to induce anti-beta(2)GPI autoantibodies or clinical disease. In contrast, autoimmunity developed in the presence of DC. Furthermore, the syngeneic beta(2)GPI was a more effective antigen than the xenogeneic protein in re-boosted animals.

CONCLUSIONS

DC effectively initiate in NZB x NZW F(1) mice self-sustaining autoimmunity against the beta(2)GPI, either associated to apoptotic cells or macropinocytosed from the serum.

In Vivo Effects of an Inhibitor of Nuclear Factor-Kappa B on Thrombogenic Properties of Antiphospholipid Antibodies

It has been shown that endothelial cell (EC) activation and tissue factor (TF) upregulation in EC and monocytes by antiphospholipid antibodies (aPL Abs) leads to a prothrombotic state and involves translocation of nuclear factor-kappa B (NF-kappaB). Here we examined the effects of an NF-kappaB inhibitor on aPL-induced thrombosis, TF activity, and EC in vivo. We treated CD1 mice with IgG from a patient with antiphospholipid syndrome (IgG-APS) or with control IgG (IgG-NHS). The adhesion of leukocytes (number of white blood cells) to EC in cremaster muscle (as an indication of EC activation) as well as the size of an induced thrombus in the femoral vein of the mice were examined. Some mice in each group were infused with 10 microM MG132 (an inhibitor of NF-kappaB). TF activity was determined using a chromogenic assay in homogenates of carotid arteries and in peritoneal cells of mice. In vivo, IgG-APS increased significantly the number of white blood cells adhering to ECs (4.7 +/- 2.2) when compared to control mice (1.5 +/- 0.8), and these effects were significantly reduced when mice were pretreated with MG132 (0.8 +/- 0.2). IgG-APS increased significantly the thrombus size and MG132 inhibited that effect (93%). Treatment of the mice with IgG-APS also induced significantly increased TF function in peritoneal cells and in homogenates of carotid arteries. Pretreatment of the mice with MG132 abrogated those effects significantly. Mice injected with IgG-APS or with IgM-APS with or without the inhibitor had medium-high titers of anticardiolipin antibodies in serum at the time of the surgical procedures. The data show that prothrombotic and proinflammatory properties of IgG-APS and IgM-APS are downregulated in vivo by an NF-kappaB inhibitor. These findings may be important in designing new modalities of targeted therapies to treat thrombosis in patients with APS.

Immunization with an apoptotic cell-binding protein recapitulates the nephritis and sequential autoantibody emergence of systemic lupus erythematosus

The initial events predisposing to loss of tolerance in patients with systemic lupus erythematosus (SLE) are largely unknown, as are the events that precipitate the transition from preclinical to overt disease. We hypothesized that induction of murine SLE would require tipping the balance between tolerance and immunity in two ways: 1) an immunogen that could take advantage of apoptotic cells as a scaffold for epitope spread, and 2) an immune activator that would generate a strong and persistent T cell response to the inciting immunogen. We show that immunization of C57BL/6 and BALB/c mice with human beta(2)-glycoprotein I, an apoptotic cell-binding protein, in the presence of LPS induces a long-lived, potent response to beta(2)-glycoprotein I that results in epitope spread to multiple SLE autoantigens. SLE-specific autoantibodies emerged in a sequential manner that recapitulated the order seen in human SLE. Moreover, immunized mice developed overt glomerulonephritis closely resembling human lupus nephritis.

Anti-beta 2 glycoprotein I antibodies in centenarians

BACKGROUND

Non-organ-specific autoantibodies are present in centenarians without evidence of autoimmune diseases but conflicting or no data on anti-phospholipid and anti-phospholipid binding proteins were reported.

OBJECTIVE

To investigate the presence and antigen specificity of anti-phospholipid and anti-phospholipid binding proteins in centenarians.

METHODS

Seventy-seven centenarians, 70 adult controls, 65 unselected elderly subjects, and 38 old SENIEUR volunteers were investigated. Anti-cardiolipin, anti-human beta 2 glycoprotein I, and lupus anticoagulant were detected. Antigen specificity was assayed against plates coated with anionic, neutral and cationic phospholipids and beta 2 glycoprotein I-dependence was also evaluated.

RESULTS

54.3% of the centenarians were positive for IgG and 8.6% for IgM anti-beta 2 glycoprotein I antibodies, while only 20.7% centenarians were positive for anti-cardiolipin IgG and 2.59% for IgM; none resulted positive for lupus anticoagulant. Anti-cardiolipin positive sera cross-reacted with negatively charged phospholipids and displayed decreased binding to serum-free cardiolipin-coated plates that was restored by human beta 2 glycoprotein I or fetal calf serum.

CONCLUSIONS

Centenarians display high reactivity against human beta 2 glycoprotein I but low binding to the bovine molecule in the anti-cardiolipin assay. In spite of the presence of antibodies comparable to those found in patients with the anti-phospholipid syndrome, no vascular events were reported suggesting the presence of unknown protective factors and/or the lack of triggering factors.

Combined search for anti–β2-glycoprotein i and anticardiolipin antibodies in antiphospholipid syndrome: Contribution to diagnosis

In this study we sought to assess (1) the diagnostic value of a combined search for anti-beta(2)-glycoprotein (abeta(2)-GPIs) and anticardiolipin antibodies (aCLs) in primary (APS I) and secondary (APS II) antiphospholipid syndrome and (2) the influence of the beta(2)-GPI preparation in the ELISA's results. abeta(2)-GPI and aCL concentrations were assessed in 70 patients with APS and compared with those in 65 patients with systemic lupus erythematosus (SLE) without clinical features of APS. In APS patients (38 with APS I, 32 with APS II), the diagnosis had to have been made at least 3 years earlier; in subjects with SLE, the diagnosis had to have been made at least 5 years earlier. All serum samples were tested for abeta(2) -GPI with the use of an in-house ELISA with an abeta(2) -GPI preparation from human plasma. Samples negative for abeta(2) -GPI were controlled with 2 additional beta(2)-GPI preparations, 1 from human serum and 1 from bovine serum. In APS, abeta(2)-GPIs were more frequent than in SLE (76% and 15%, respectively; P <.0001), mainly with IgG isotype and with significantly higher levels than those found in SLE. The specificity for APS was 92% for IgG abeta(2)-GPIs and 68% for IgG aCLs. The highest association with APS was found for the combination of the 2 markers (odds ratio 29; 95% confidence interval 10-76; P <.0001). Among the APS patients, 6 were positive for aCL only and remained negative regardless of which beta 2 -GPI preparation was used; 1 patient was aCL-negative and only positive with human beta 2 -GPI. These data emphasize the heterogeneity of the APS immunologic profile and the diagnostic possibilities of both antibodies.

Beta-2 glycoprotein I and its role in antiphospholipid syndrome—lessons from knockout mice

The antiphospholipid syndrome is characterized by the presence in serum of autoantibodies against beta2GPI. Although the role of beta2GPI in the pathogenesis of antiphospholipid antibody syndrome (APS) is well recognized, its exact physiological functions still remain undisclosed. Several interactions of beta2GPI with components of the coagulation cascade have been proposed, resulting in both procoagulant and anticoagulant effects. Additionally, beta2GPI has been implicated in the mechanism of recurrent fetal loss entailed in APS. Recently, using a homologous recombination approach, reproduction of mice homozygous for deletion of the beta2GPI gene has been feasible. beta2GPI knockout mice offer a valuable tool for revealing the physiological role of the protein. These mice show decreased in vitro ability for thrombin generation. Furthermore, although mice lacking beta2GPI are fertile, the success of early pregnancy is moderately compromised and functional beta2GPI is believed necessary for optimal implantation and placental morphogenesis.

Requirement of dying cells and environmental adjuvants for the induction of autoimmunity

OBJECTIVE

Cells commonly die without eliciting autoimmunity. However, dying cells are a potential initiating stimulus for systemic lupus erythematosus (SLE). Our goal was to verify whether immune adjuvants influence the autoimmunity induction that ensues following in vivo injection of dying cells.

METHODS

Mice were immunized with apoptotic thymocytes in the presence of artificial moieties, such as Freund's incomplete adjuvant (IFA), or natural adjuvants, such as dendritic cells (DCs). Renal involvement and the development of autoantibodies were monitored.

RESULTS

Apoptotic cells failed to induce clinical disease or to sustain production of autoantibodies in (NZB x NZW)F(1) mice. In contrast, autoimmunity developed in the presence of IFA or DCs. The characteristics of the adjuvant influenced the array of autoantibodies, the kinetics of their development, and the severity of the disease. DCs were required for induction of anti-beta(2)-glycoprotein I IgG. Adjuvants alone did not elicit disease.

CONCLUSION

A "two-hit" signal composed of autoantigens and adjuvants initiates systemic autoimmunity. Moreover, environmental signals at the site of clearance of dead cells shape the features and the severity of the autoimmune disease. Strategies aimed at preventing the accumulation of dying cells and at modulating endogenous adjuvants may be beneficial for the treatment of SLE.

A murine model of type 2 autoimmune hepatitis: Xenoimmunization with human antigens

Autoimmune hepatitis (AIH) is characterized by an immune-mediated injury of the hepatic parenchyma of unknown pathogenesis. Type 2 AIH is identified by the presence of anti-liver-kidney microsomes type 1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1) autoantibodies. The current study shows that a murine model of AIH can be generated by DNA immunization against type 2 AIH self-antigens (P450 2D6 and formiminotransferase-cyclodeaminase). A pCMV plasmid containing the N-terminal region of mouse CTLA-4 and the antigenic region of human CYP2D6 (672-1,377 bp) and human formiminotransferase cyclodeaminase (FTCD; 1,232-1,668 bp) was used for DNA immunization of C57BL/6 female mice. Immunized mice showed elevated levels of alanine aminotransferase (ALT), with peaks at 4 and 7 months postinjection. Periportal, portal, and intralobular liver inflammatory infiltrates were observed at histology. Mainly CD4+ lymphocytes, but also CD8+ and B lymphocytes, were found in the liver. Cytotoxic-specific T cells were found in both the liver and spleen of these animals. Mice developed anti-LKM1 and anti-LC1 antibodies of immunoglobulin G2 (IgG2) subclass, against specific mouse autoantigens. The ALT levels correlated with both the presence of anti-LKM1/anti-LC1 antibodies and the presence of liver necroinflammation. In conclusion, in mice, DNA immunization against human autoantigens breaks tolerance and induces an autoimmune liver disease. Molecular mimicry between foreign and self-antigens explains the liver injury. This model of AIH resembles human type 2 AIH and will be helpful for the study of its pathogenesis.