Zealand Black Research Articles

Augmentation of NZB Autoimmune Phenotypes by the Sle1c Murine Lupus Susceptibility Interval

The Sle1c lupus susceptibility interval spans a 7-Mb region on distal murine chromosome 1. Cr2 is the strongest candidate gene for lupus susceptibility in this interval, as its protein products are structurally and functionally altered. B6.Sle1c congenic mice develop Abs to chromatin by 9 mo of age with a 30% penetrance and do not develop GN. To determine whether the New Zealand White (NZW)-derived Sle1c interval would interact with New Zealand Black (NZB) genes to result in enhanced autoimmune phenotypes, NZB mice were bred with B6 or B6.Sle1c congenic mice and approximately 20 female offspring were selected from each breeding for longitudinal study. These mice differ only at the Sle1c locus at which they have either a NZB/B6 or NZB/NZW genotype. NZB x B6.Sle1c mice had an accelerated onset of anti-chromatin Abs (100 vs 68% at 6 mo, p = 0.006) and anti-dsDNA Abs (45 vs 5% at 9 mo, p = 0.0048). Furthermore, median titers of anti-chromatin and anti-dsDNA Abs were significantly higher in the NZB x B6.Sle1c group compared with the NZB x B6 group. This corresponded with a higher prevalence of proliferative GN at 12 mo (55 vs 16%, p = 0.0214) as well as increased glomerular deposition of C3 (p = 0.0272) and IgG (p = 0.032), although blood urea nitrogen remained normal and significant proteinuria was not identified in either group. These data show that the Sle1c interval accelerates and augments the loss of tolerance to chromatin and dsDNA induced by NZB genes and induces significantly greater end-organ damage.

Dissociation of the Genetic Loci Leading to B1a and NKT Cell Expansions from Autoantibody Production and Renal Disease in B6 Mice with an Introgressed New Zealand Black Chromosome 4 Interval

Previous mapping studies have linked New Zealand Black (NZB) chromosome 4 to several lupus traits, including autoantibody production, splenomegaly, and glomerulonephritis. To confirm the presence of these traits, our laboratory introgressed homozygous NZB chromosome 4 intervals extending from either 114 to 149 Mb or 32 to 149 Mb onto the lupus-resistant C57BL/6 background (denoted B6.NZBc4S and B6.NZBc4L, respectively). Characterization of aged cohorts revealed that B6.NZBc4L mice exhibited a striking increase in splenic B1a and NKT cells in the absence of high titer autoantibody production and significant renal disease. Tissue-specific expansion of these subsets was also seen in the peritoneum and liver for B1a cells and in the bone marrow for NKT cells. Staining with CD1d tetramers loaded with an alpha-galactosylceramide analog (PBS57) demonstrated that the expanded NKT cell population was mainly CD1d-dependent NKT cells. The lack of both cellular phenotypes in B6.NZBc4S mice demonstrates that the genetic polymorphism(s) that result in these phenotypes are on the proximal region of NZB chromosome 4. This study confirms the presence of a locus that promotes the expansion of B1a cells and newly identifies a region that promotes CD1d-restricted NKT cell expansion on NZB chromosome 4. Taken together, the data indicate that neither an expansion of B1a cells and/nor NKT cells is sufficient to promote autoantibody production and ultimately, renal disease.

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 × NZW F1) with syngeneic dendritic cells (DC) that had macropinocytosed β2-glycoprotein 1 (β2GPI) during propagation in normal mouse serum or that had phagocytosed apoptotic thymocytes with syngeneic (murine) or xenogeneic (bovine) β2GPI, which was associated to plasma membrane of the cells. Mice were in parallel immunized with apoptotic thymocytes that had associated the β2GPI to their membranes in the absence of DC. The development of anti-β2GPI antibodies and clinical features were monitored.Results. Apoptotic cells alone, opsonized with β2GPI, failed to induce anti-β2GPI autoantibodies or clinical disease. In contrast, autoimmunity developed in the presence of DC. Furthermore, the syngeneic β2GPI was a more effective antigen than the xenogeneic protein in re-boosted animals.Conclusions. DC effectively initiate in NZB × NZW F1 mice self-sustaining autoimmunity against the β2GPI, either associated to apoptotic cells or macropinocytosed from the serum.

Comparative immunobiology of thymic DC mRNA in autoimmune-prone mice

New Zealand Black (NZB) mice have multiple defects in both innate and acquired immunity. A fundamental defect, described more than 25 years ago, is premature thymic involution. Subsequent studies have disclosed multiple defects in thymic epithelial cells, and it has been proposed that thymic dendritic cells (DCs) play an important role not only in thymic involution but also in the appearance of immunopathology. However, the number of available thymic DCs makes this population extremely difficult to study. We have taken advantage of our ability to isolate pure populations of thymic DCs and have examined several key mRNA levels of enzymes involved in signal transduction. Our data on NZB mice was compared to that of NZB x NZW F1 (B/WF1), BXSB- Yaa, MRL/ lpr, NOD and control mice. Importantly, we demonstrate herein that a common feature in autoimmune-prone mice is an increase of thymic DC c-met mRNA. Indeed, the increase in c-met mRNA levels appeared specific to the thymus and was not noted in the spleen. Additionally, we demonstrate that E-cadherin, a downstream molecule of c-met, is also reduced. Finally, we note that the levels of HGF mRNA are normal in the autoimmune strains examined herein, confirming that the abnormality of c-met mRNA is not due to primary defects in thymic stromal cells. We submit that these results highlight the possibility of a selective defect in thymic DCs which will be a pivotal step in loss of tolerance, and suggest that future studies focus on adoptive cell transfer involving this population.

Pancreatic Autoimmunity Induction with Insulin B:9–23 Peptide and Viral Mimics in the NZB Mouse

To create a new experimental model of diabetes, we used the New Zealand Black (NZB) mouse as a potential model. NZB mice were immunized with B:9-23 insulin peptide in IFA and the viral mimic, poly(A:U). No diabetes was observed but blood glucose was significantly higher in the B:9-23 peptide group compared to controls. Insulin autoantibodies (IAA) were only induced in groups given the B:9-23 peptide. B:9-23 alone induced peri-insulitis. We demonstrate insulin autoimmunity in the NZB mouse using the insulin peptide B:9-23 and viral mimics. The reason for the protection from diabetes despite the presence of autoimmunity is currently not established.

Suppression of Disease in New Zealand Black/New Zealand White Lupus-Prone Mice by Adoptive Transfer of Ex Vivo Expanded Regulatory T Cells

An increasing number of studies indicate that a subset of CD4(+) T cells with regulatory capacity (regulatory T cells; T(regs)) can function to control organ-specific autoimmune disease. To determine whether abnormalities of thymic-derived T(regs) play a role in systemic lupus erythematosus, we evaluated T(reg) prevalence and function in (New Zealand Black x New Zealand White)F(1) (B/W) lupus-prone mice. To explore the potential of T(regs) to suppress disease, we evaluated the effect of adoptive transfer of purified, ex vivo expanded thymic-derived T(regs) on the progression of renal disease. We found that although the prevalence of T(regs) is reduced in regional lymph nodes and spleen of prediseased B/W mice compared with age-matched non-autoimmune mice, these cells increase in number in older diseased mice. In addition, the ability of these cells to proliferate in vitro was comparable to those purified from non-autoimmune control animals. Purified CD4(+)CD25(+)CD62L(high) B/W T(regs) were expanded ex vivo 80-fold, resulting in cells with a stable suppressor phenotype. Adoptive transfer of these exogenously expanded cells reduced the rate at which mice developed renal disease; a second transfer after treated animals had developed proteinuria further slowed the progression of renal disease and significantly improved survival. These studies indicate that thymic-derived T(regs) may have a significant role in the control of autoimmunity in lupus-prone B/W mice, and augmentation of these cells may constitute a novel therapeutic approach for systemic lupus erythematosus.

Effects of tripterine on mRNA expression of TGF‐β1 and collagen IV expression in BW F1 mice

Tripterine is a chemical isolated from a traditional Chinese herb which had been testified for its anti-inflammatory and immunosuppressive activities in a previous study. However, little is known about the effects and mechanism of action of Tripterine on treating lupus nephritis. In the present study we investigated the effect of Tripterine on the F1 hybrids of New Zealand Black (NZB) and New Zealand White (NZW) mice which functioned as a model of human systemic lupus erythematosus (BW F1 mice) and evaluated the possible mechanism implicated in the mRNA expression of TGF-beta1 and collagen IV expression of the BW F1 mice kidney tissue. Different doses of Tripterine were injected peritoneally to BW F1 mice at different stages to study the preventive effects of Tripterine on lupus nephritis glomerulosclerosis and its mechanisms. Twenty-four hour urine protein excretion, serum anti-dsDNA antibodies and the expression of collagen type IV were examined by immunohistochemistry while the expression of TGF-beta1 mRNA was detected by RT nested PCR. Tripterine decreased urine protein excretion and the level of serum anti-dsDNA antibodies and also suppressed the expression of collagen type IV and TGF-beta1 mRNA in the murine kidney tissue. Administration of Tripterine before the occurrence of proteinuria had much greater protective effects than if it was administered after the occurrence of proteinuria. No significant difference was found between the 3 mg/kg/week Tripterine-treated-group and the 6 mg/kg/week Tripterine-treated-group. Tripterine had a definite protective effect on glomerulosclerosis of the lupus murine model. Tripterine could significantly reduce the amount of urine protein excretion, suppress the formation of serum anti-dsDNA antibodies, it could also efficiently decrease the expression of renal collagen type IV probably due to its suppressive effect on the expressions of local TGF-(1 mRNA) in this model.

Increased Expression of Ifi202, an IFN-Activatable Gene, in B6.Nba2 Lupus Susceptible Mice Inhibits p53-Mediated Apoptosis

Increased expression of p202 protein (encoded by the Ifi202 gene) in splenocytes derived from B6.Nba2 mice (congenic for the Nba2 interval derived from the New Zealand Black mice) was correlated with defects in apoptosis of splenic B cells and increased susceptibility to develop systemic lupus erythematosus. We have now investigated the molecular mechanisms by which increased expression of p202 in B6.Nba2 cells contributes to defects in apoptosis. In this study, we report that increased expression of p202 in the B6.Nba2 splenocytes, as compared with cells derived from the parental C57BL/6 (B6) mice, was correlated with increased levels of p53 protein and inhibition of p53-mediated transcription of target genes that encode proapoptotic proteins. Conversely, knockdown of p202 expression in B6.Nba2 cells resulted in stimulation of p53-mediated transcription. We found that p202 bound to p53 in the N-terminal region (aa 44-83) comprising the proline-rich region that is important for p53-mediated apoptosis. Consistent with the binding of p202 to p53, increased expression of p202 in B6.Nba2 mouse embryonic fibroblasts inhibited UV-induced apoptosis. Taken together, our observations support the idea that increased expression of p202 in B6.Nba2 mice increases the susceptibility to develop lupus, in part, by inhibiting p53-mediated apoptosis.

Functional Interplay between Intrinsic B and T Cell Defects Leads to Amplification of Autoimmune Disease in New Zealand Black Chromosome 1 Congenic Mice

Genetic loci on New Zealand Black (NZB) chromosome 1 play an important role in the development of lupus-like autoimmune disease. We have shown previously that C57BL/6 mice with an introgressed NZB chromosome 1 interval extending from approximately 35 to 106 cM have significantly more severe autoimmunity than mice with a shorter interval extending from approximately 82 to 106 cM. Comparison of the cellular phenotype in these mice revealed that both mouse strains had evidence of increased T cell activation; however, activation was more pronounced in mice with the longer interval. Mice with the longer interval also had increased B cell activation, leading us to hypothesize that there were at least two independent lupus susceptibility loci on chromosome 1. In this study, we have used mixed hemopoietic radiation chimeras to demonstrate that autoimmunity in these mice arises from intrinsic B and T cell functional defects. We further show that a T cell defect, localized to the shorter interval, leads to spontaneous activation of T cells specific for nucleosome histone components. Despite activation of self-reactive T cells in mixed chimeric mice, only chromosome 1 congenic B cells produce anti-nuclear Abs and undergo class switching, indicating impaired B cell tolerance mechanisms. In mice with the longer chromosome 1 interval, an additional susceptibility locus exacerbates autoimmune disease by producing a positive feedback loop between T and B cell activation. Thus, T and B cell defects act in concert to produce and amplify the autoimmune phenotype.

Aberrant IgM Signaling Promotes Survival of Transitional T1 B Cells and Prevents Tolerance Induction in Lupus-Prone New Zealand Black Mice

New Zealand Black (NZB) mice develop a lupus-like syndrome. Although the precise immune defects leading to autoantibody production in these mice have not been characterized, they possess a number of immunologic abnormalities suggesting that B cell tolerance may be defective. In the bone marrow, immature self-reactive B cells that have failed to edit their receptors undergo apoptosis as a consequence of Ig receptor engagement. Splenic transitional T1 B cells are recent bone marrow emigrants that retain these signaling properties, ensuring that B cells recognizing self-Ags expressed only in the periphery are deleted from the naive B cell repertoire. In this study we report that this mechanism of tolerance is defective in NZB mice. We show that NZB T1 B cells are resistant to apoptosis after IgM cross-linking in vitro. Although extensive IgM cross-linking usually leads to deletion of T1 B cells, in NZB T1 B cells we found that it prevents mitochondrial membrane damage, inhibits activation of caspase-3, and promotes cell survival. Increased survival of NZB T1 B cells was associated with aberrant up-regulation of Bcl-2 after Ig receptor engagement. We also show that there is a markedly increased proportion of NZB T1 B cells that express elevated levels of Bcl-2 in vivo and provide evidence that up-regulation of Bcl-2 follows encounter with self-Ag in vivo. Thus, we propose that aberrant cell signaling in NZB T1 B cells leads to the survival of autoreactive B cells, which predisposes NZB mice to the development of autoimmunity.

Inducible Nitric Oxide Synthase Inhibitors Reduce Urinary Markers of Systemic Oxidant Stress in Murine Proliferative Lupus Nephritis

BackgroundProliferative lupus nephritis (PLN) is characterized by increased expression of inducible nitric oxide (NO) synthase (iNOS). Inhibition of iNOS with NG-monomethyl L-arginine (L-NMMA) abrogates renal disease in two models of...

Colocalization of Expansion of the Splenic Marginal Zone Population with Abnormal B Cell Activation and Autoantibody Production in B6 Mice with an Introgressed New Zealand Black Chromosome 13 Interval

Polyclonal B cell activation is a prominent feature of the lupus-prone New Zealand Black (NZB) mouse strain. We have previously demonstrated linkage between a region on NZB chromosome 13 and increased costimulatory molecule expression on B cells. In this study we have produced C57BL/6 congenic mice with an introgressed homozygous NZB interval extending from approximately 24 to 73 cM on chromosome 13 (denoted B6.NZBc13). We show that B6.NZBc13 female mice not only have enhanced B cell activation but also share many other B cell phenotypic characteristics with NZB mice, including expansion of marginal zone and CD5+ B cell populations, increased numbers of IgM ELISPOTs, and increased serum levels of total IgM and IgM autoantibodies. In addition these mice have increased T cell activation, increased numbers of germinal centers, mild glomerulonephritis, and produce high-titer IgM and IgG anti-chromatin Abs. Male B6.NZBc13 mice have a less pronounced cellular phenotype, lacking expansion of the marginal zone B cell population and IgG anti-chromatin Ab production, indicating the presence of gender dimorphism for this locus. Thus, we have identified a genetic locus that recapitulates with fidelity the B cell phenotypic abnormalities in NZB mice, and we demonstrate that this locus is sufficient to induce an autoimmune phenotype. The data provide further support to the contention that immune abnormalities leading to altered B cell activation and selection contribute to the development of autoimmunity in NZB mice.

T Cell Tolerance to Germline-Encoded Antibody Sequences in a Lupus-Prone Mouse

The BCR V region has been implicated as a potential avenue of T cell help for autoreactive B cells in systemic lupus erythematosus. In principle, either germline-encoded or somatically generated sequences could function as targets of such help. Preceding studies have indicated that class II MHC-restricted T cells in normal mice attain a state tolerance to germline-encoded Ab diversity. In this study, we tested whether this tolerance is intact in systemic lupus erythematosus-prone (New Zealand Black x SWR)F1 mice (SNF1). Using a hybridoma sampling approach, we found that SNF1 T cells were tolerant to germline-encoded Ab sequences. Specifically, they were tolerant to germline-encoded sequences derived from a lupus anti-chromatin Ab that arose spontaneously in this strain. This was true both for diseased and prediseased mice. Thus, there does not appear to be a global defect in T cell tolerance to Ab V regions in this autoimmune-prone strain either before or during autoimmune disease.

Failed Up-Regulation of the Inhibitory IgG Fc Receptor FcγRIIB on Germinal Center B Cells in Autoimmune-Prone Mice Is Not Associated with Deletion Polymorphisms in the Promoter Region of the FcγRIIB Gene

FcgammaRIIB, a low-affinity FcR for IgG, inhibits BCR-mediated activation when these two receptors are co-cross-linked by Ags and IgG-containing immune complexes. Although a role for FcgammaRIIB in the germinal center (GC) reaction has been proposed, conflicting results have been published regarding the levels of FcgammaRIIB expressed on GC B cells in normal and autoimmune-prone mice and humans. In the present study, we investigate this issue in detail in mice by using multiple GC B cell markers, two different antigenic systems, primary and secondary GC responses, and by excluding the influence of splenic influx of immature B cells and passive acquisition of FcgammaRIIB from follicular dendritic cells. Our results are in concordance with previous data indicating that FcgammaRIIB expression is up-regulated on GC B cells in normal mice. In contrast, we observe comparable levels of FcgammaRIIB on GC and non-GC B cells in New Zealand White, New Zealand Black, and B6.Sle1 autoimmune-prone strains. Therefore, we suggest that these strains exhibit failed up-regulation of FcgammaRIIB on GC B cells, rather than down-regulation, as previously suggested. Also, in contrast to previous indications, this perturbed regulation is not uniquely associated with deletion polymorphisms in the promoter region of the FcgammaRIIB gene but does appear to be independent of genetic background. Finally, we present evidence indicating that FcgammaRIII, a low-affinity activating IgG FcR, is expressed on the GC B cells of normal but not autoimmune-prone mice.

Expansion and Hyperactivity of CD1d-Restricted NKT Cells during the Progression of Systemic Lupus Erythematosus in (New Zealand Black × New Zealand White)F1 Mice

CD1d-restricted NKT cells expressing invariant TCR alpha-chain rearrangements (iNKT cells) have been reported to be deficient in humans with a variety of autoimmune syndromes and in certain strains of autoimmune mice. In addition, injection of mice with alpha-galactosylceramide, a specific glycolipid agonist of iNKT cells, activates these T cells and ameliorates autoimmunity in several different disease models. Thus, deficiency and reduced function in iNKT cells are considered to be risk factors for the development of such diseases. In this study we report that the development of systemic lupus erythematosus in (New Zealand Black (NZB) x New Zealand White (NZW))F(1) mice was paradoxically associated with an expansion and activation of iNKT cells. Although young (NZB x NZW)F(1) mice had normal levels of iNKT cells, these expanded with age and became phenotypically and functionally hyperactive. Activation of iNKT cells in (NZB x NZW)F(1) mice in vivo or in vitro with alpha-galactosylceramide indicated that the immunoregulatory role of iNKT cells varied over time, revealing a marked increase in their potential to contribute to production of IFN-gamma with advancing age and disease progression. This evolution of iNKT cell function during the progression of autoimmunity may have important implications for the mechanism of disease in this model of systemic lupus erythematosus and for the development of therapies using iNKT cell agonists.

Regulation of the Expression of Caspase-9 by the Transcription Factor Activator Protein-4 in Glucocorticoid-induced Apoptosis

Caspase-9 (Casp-9) induces death signals by triggering other types of caspase activation, and its expression greatly influences the onset of apoptosis. During the isolation of apoptosis-related genes involved in glucocorticoid (GC)-induced cell death in murine thymic lymphomas, we found that the antisense gene of the transcription factor activator protein-4 (AP-4) inhibited dexamethasone-induced apoptosis. Western blot analysis revealed that the expression of Bcl-xL, Bax, and Apaf-1 was not affected in cells transfected with sense or antisense AP-4 genes. In contrast, both the expression and activation of Casp-9 were inhibited in the antisense AP-4 transfectants. We isolated the 2.4-kb 5'-flanking region of Casp-9, and the promoter activity was investigated. We found the AP-4-binding sites at -1.55 and -1.38 kb to be responsible for the promoter activity. Furthermore, a negative cis-element was expected to exist between bases -1140 and -944. When the cells were treated with dexamethasone, a rapid down-regulation of AP-4 and Casp-9 was observed whether the cells were GC-sensitive lymphomas or GC-insensitive L929 fibroblast cells. In addition, L929 cells pretreated with dexamethasone were found to be resistant to subsequent treatment with etoposide, an apoptosis-inducing reagent. GC has a two-sided effect on apoptosis, i.e. a pro-apoptotic effect on certain cell types and a prosurvival effect on other cell types. Our findings will explain, at least in part, this effect.

Breakdown of Mucosal Immunity in the Gut and Resultant Systemic Sensitization by Oral Antigens in a Murine Model for Systemic Lupus Erythematosus

Secreted IgA plays a pivotal role in the mucosal immunity to maintain the front line of body defense. We found that the level of fecal IgA was dramatically decreased in aged (NZB x NZW)F(1) (BWF(1)) mice developing lupus nephritis, whereas levels in similarly aged New Zealand Black (NZB) and New Zealand White (NZW) mice remained unchanged compared with young mice. The number of cells obtained from Peyer's patches was markedly decreased in aged BWF(1) mice. Aged BWF(1) mice showed increased susceptibility to pathogenic bacterial infection. Furthermore, oral administration of OVA failed to inhibit secondary IgG response induced by systemic immunization, suggesting defective oral tolerance in aged BWF(1) mice. A significant amount of orally administered OVA was incorporated directly into the intestinal lamina propria in aged BWF(1) mice whereas it was mainly localized in subepithelial domes and interfollicular region in Peyer's patches in young mice. T cells obtained from renal and pulmonary lymph nodes of aged BWF(1) mice that had been orally administered with OVA showed an Ag-specific T cell proliferation, whereas those from young BWF(1), aged NZB, and aged NZW mice did not. Interestingly, aerosol exposure to OVA of aged BWF(1) mice, which had been orally administered with the same Ag, provoked an eosinophil infiltration in the lung. These results demonstrate that mucosal immunity in the gut is impaired and oral Ags induce systemic sensitization instead of oral tolerance in the development of murine lupus.

Autoimmune Alterations Induced by the New Zealand BlackLbw2Locus in BWF1 Mice

The New Zealand Black (NZB) Lbw2 locus (lupus NZB x New Zealand White (NZW) 2 locus) was previously linked to mortality and glomerulonephritis, but not to IgG autoantibodies, suggesting that it played a role in a later disease stage. To define its contribution, (NZB x NZW)F1 hybrids (BWF1) containing two, one, or no copies of this locus were generated. Lack of the NZB Lbw2 indeed reduced mortality and glomerulonephritis, but not serum levels of total and anti-DNA IgG Abs. There were, however, significant reductions in the B cell response to LPS, total and anti-DNA IgM and IgG Ab-forming cells, IgM Ab levels, and glomerular Ig deposits. Furthermore, although serum IgG autoantibody levels correlated poorly with kidney IgG deposits, the number of spontaneous IgG Ab-forming cells had a significant correlation. Genome-wide mapping of IgM anti-chromatin levels identified only Lbw2, and analysis of subinterval congenics tentatively reduced Lbw2 to approximately 5 Mb. Because no known genes associated with B cell activation and lupus are in this interval, Lbw2 probably represents a novel B cell activation gene. These findings establish the importance of Lbw2 in the BWF1 hybrid and indicate that Lbw2, by enhancing B cell hyperactivity, promotes the early polyclonal activation of B cells and subsequent production of autoantibodies.

IFN-α Induces Early Lethal Lupus in Preautoimmune (New Zealand Black × New Zealand White)F1 but Not in BALB/c Mice

Recent studies indicate that IFN-alpha is involved in pathogenesis of systemic lupus erythematosus. However, direct proof that IFN-alpha is not only necessary, but also sufficient to induce lupus pathogenicity is lacking. In this study, we show that in vivo adenovector-mediated delivery of murine IFN-alpha results in preautoimmune (New Zealand Black (NZB) x New Zealand White (NZW))F(1), but not in normal, mice, in a rapid and severe disease with all characteristics of systemic lupus erythematosus. Anti-dsDNA Abs appeared as soon as day 10 after initiation of IFN-alpha treatment. Proteinuria and death caused by glomerulonephritis occurred in all treated mice within, respectively, approximately 9 and approximately 18 wk, at a time when all untreated (NZB x NZW)F(1) did not show any sign of disease. IFN-alpha in vivo induced an overexpression of B lymphocyte stimulator in circulation at similar levels in both the preautoimmune and the normal mouse strains. All effects elicited by IFN-alpha were dose dependent. (NZB x NZW)F(1) infused with purified murine IFN-alpha also showed acceleration of lupus. Thus, prolonged expression of IFN-alpha in vivo induces early lethal lupus in susceptible animals.

Differential Role of Three Major New Zealand Black-Derived Loci Linked with Yaa-Induced Murine Lupus Nephritis

By assessing the development of Y-linked autoimmune acceleration (Yaa) gene-induced systemic lupus erythematosus in C57BL/6 (B6) x (New Zealand Black (NZB) x B6.Yaa)F(1) backcross male mice, we mapped three major susceptibility loci derived from the NZB strain. These three quantitative trait loci (QTL) on NZB chromosomes 1, 7, and 13 differentially regulated three different autoimmune traits: anti-nuclear autoantibody production, gp70-anti-gp70 immune complex (gp70 IC) formation, and glomerulonephritis. Contributions to the disease traits were further confirmed by generating and analyzing three different B6.Yaa congenic mice, each carrying one individual NZB QTL. The chromosome 1 locus that overlapped with the previously identified Nba2 (NZB autoimmunity 2) locus regulated all three traits. A newly identified chromosome 7 locus, designated Nba5, selectively promoted anti-gp70 autoantibody production, hence the formation of gp70 IC and glomerulonephritis. B6.Yaa mice bearing the NZB chromosome 13 locus displayed increased serum gp70 production, but not gp70 IC formation and glomerulonephritis. This locus, called Sgp3 (serum gp70 production 3), selectively regulated the production of serum gp70, thereby contributing to the formation of nephritogenic gp70 IC and glomerulonephritis, in combination with Nba2 and Nba5 in NZB mice. Among these three loci, a major role of Nba2 was demonstrated, because B6.Yaa Nba2 congenic male mice developed the most severe disease. Finally, our analysis revealed the presence in B6 mice of an H2-linked QTL, which regulated autoantibody production. This locus had no apparent individual effect, but most likely modulated disease severity through interaction with NZB-derived susceptibility loci.