Genetic analysis of the NZB contribution to lupus-like autoimmune disease in (NZB x NZW)F1 mice

Dietary restriction regimens for fighting kidney disease: Insights from rodent studies

This review critically discusses the research findings on the effects of various dietary restriction regimens in rodent models of kidney disease. Long-term caloric restriction executed at both early and progressive stages of kidney disease was found to exert beneficial effects in rodents. Moreover, some studies have also demonstrated the efficacy of short-term caloric restriction in treating the kidney disease of variable aetiologies possibly by improving mitochondrial dysfunction, autophagy process and suppression of inflammation. However, the mechanisms underlying these short-term caloric restriction mediated protective effects in rodent models of kidney disease are not completely understood. Importantly, few available evidences have also suggested that carbohydrate restriction can exert beneficial effects in aging and experimentally induced renal injury models, but the mechanisms are not explored yet. Interestingly, the benefits of low protein diet in kidney disease models are extensively reported in literature. However, in most of these studies implementation of the low protein dietary regimen was found to associated with increased high carbohydrate and caloric intake (non-isocaloric). Thus, testing the effects of low protein diet under isocaloric conditions might further help to particularly understand the role of dietary protein content in pathology of kidney disease. Moreover, the direct evidences comparing the efficacy of various dietary restriction regimens in rodent models of kidney diseases are also scarce at present.

An Lck-cre transgene accelerates autoantibody production and lupus development in (NZB × NZW)F1 mice

Lupus is an autoimmune disease characterized by the development of antinuclear autoantibodies and immune complex-mediated tissue damage. T cells in lupus patients appear to undergo apoptosis at an increased rate, and this enhanced T cell apoptosis has been postulated to contribute to lupus pathogenesis by increasing autoantigen load. However, there is no direct evidence to support this hypothesis. In this study, we show that an Lck-cre transgene, which increases T cell apoptosis as a result of T cell-specific expression of cre recombinase, accelerates the development of autoantibodies and nephritis in lupus-prone (NZB × NZW)F1 mice. Although the enhanced T cell apoptosis in Lck-cre transgenic mice resulted in an overall decrease in the relative abundance of splenic CD4(+) and CD8(+) T cells, the proportion of activated CD4(+) T cells was increased and no significant change was observed in the relative abundance of suppressive T cells. We postulate that the Lck-cre transgene promoted lupus by enhancing T cell apoptosis, which, in conjunction with the impaired clearance of apoptotic cells in lupus-prone mice, increased the nuclear antigen load and accelerated the development of anti-nuclear autoantibodies. Furthermore, our results also underscore the importance of including cre-only controls in studies using the cre-lox system.

Chance, genetics, and the heterogeneity of disease and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a remarkably complex and heterogeneous systemic autoimmune disease. Disease complexity within individuals and heterogeneity among individuals, even genetically identical individuals, is driven by stochastic execution of a complex inherited program. Genome-wide association studies (GWAS) have progressively improved understanding of which genes are most critical to the potential for SLE and provided illuminating insight about the immune mechanisms that are engaged in SLE. What initiates expression of the genetic program to cause SLE within an individual and how that program is initiated remains poorly understood. If we extrapolate from all of the different experimental mouse models for SLE, we can begin to appreciate why SLE is so heterogeneous and consequently why prediction of disease outcome is so difficult. In this review, we critically evaluate extrinsic versus intrinsic cellular functions in the clearance and elimination of cellular debris and how dysfunction in that system may promote autoimmunity to nuclear antigens. We also examine several mouse models genetically prone to SLE either because of natural inheritance or inheritance of induced mutations to illustrate how different immune mechanisms may initiate autoimmunity and affect disease pathogenesis. Finally, we describe the heterogeneity of disease manifestations in SLE and discuss the mechanisms of disease pathogenesis with emphasis on glomerulonephritis. Particular attention is given to discussion of how anti-DNA autoantibody initiates experimental lupus nephritis (LN) in mice.

Genome-wide genetic study in autoimmune disease-prone mice

Mouse models of autoimmune diseases provide invaluable insights into the cellular and molecular bases of autoimmunity. Genetic linkage studies focusing on their abnormal quantitative phenotypes in relation to the loss of self-tolerance will lead to the identification of polymorphic genes that play pivotal roles in the genetic predisposition to autoimmunity. In this chapter, we first overview the basic concepts in the statistical genetics and then provide guides to genotyping microsatellite DNA markers and to quantitative trait loci mapping using a MAPMAKER program.

Epistatic suppression of fatal autoimmunity in New Zealand black bicongenic mice

Numerous mapping studies have implicated genetic intervals from lupus-prone New Zealand Black (NZB) chromosomes 1 and 4 as contributing to lupus pathogenesis. By introgressing NZB chromosomal intervals onto a non-lupus-prone B6 background, we determined that: NZB chromosome 1 congenic mice (denoted B6.NZBc1) developed fatal autoimmune-mediated kidney disease, and NZB chromosome 4 congenic mice (denoted B6.NZBc4) exhibited a marked expansion of B1a and NKT cells in the surprising absence of autoimmunity. In this study, we sought to examine whether epistatic interactions between these two loci would affect lupus autoimmunity by generating bicongenic mice that carry both NZB chromosomal intervals. Compared with B6.NZBc1 mice, bicongenic mice demonstrated significantly decreased mortality, kidney disease, Th1-biased IgG autoantibody isotypes, and differentiation of IFN-γ-producing T cells. Furthermore, a subset of bicongenic mice exhibited a paucity of CD21(+)CD1d(+) B cells and an altered NKT cell activation profile that correlated with greater disease inhibition. Thus, NZBc4 contains suppressive epistatic modifiers that appear to inhibit the development of fatal NZBc1 autoimmunity by promoting a shift away from a proinflammatory cytokine profile, which in some mice may involve NKT cells.

Genetically determined Amerindian ancestry correlates with increased frequency of risk alleles for systemic lupus erythematosus

OBJECTIVE

To assess whether genetically determined Amerindian ancestry predicts increased presence of risk alleles of known susceptibility genes for systemic lupus erythematosus (SLE).

METHODS

Single-nucleotide polymorphisms (SNPs) within 16 confirmed genetic susceptibility loci for SLE were genotyped in a set of 804 Mestizo lupus patients and 667 Mestizo healthy controls. In addition, 347 admixture informative markers were genotyped. Individual ancestry proportions were determined using STRUCTURE. Association analysis was performed using PLINK, and correlation between ancestry and the presence of risk alleles was analyzed using linear regression.

RESULTS

A meta-analysis of the genetic association of the 16 SNPs across populations showed that TNFSF4, STAT4, ITGAM, and IRF5 were associated with lupus in a Hispanic Mestizo cohort enriched for European and Amerindian ancestry. In addition, 2 SNPs within the major histocompatibility complex region, previously shown to be associated in a genome-wide association study in Europeans, were also associated in Mestizos. Using linear regression, we predicted an average increase of 2.34 risk alleles when comparing an SLE patient with 100% Amerindian ancestry versus an SLE patient with 0% Amerindian ancestry (P < 0.0001). SLE patients with 43% more Amerindian ancestry were predicted to carry 1 additional risk allele.

CONCLUSION

Our results demonstrate that Amerindian ancestry is associated with an increased number of risk alleles for SLE.

Autosomal loci associated with a sex-related difference in the development of autoimmune phenotypes in a lupus model

Sex-related differences (SrD) are a general characteristic of human autoimmune diseases. There is an increasing body of evidence that suggests a link between sex-related hormones and autoimmune onsets. Here, through a genetic approach using a lupus mouse model, we attempted to show the involvement of genetic factors in the development of SrD in autoimmune diseases. Using MRL/lpr x (MRL/lpr x C57BL/6.Fas(lpr))F1 (MBN2) mice, the whole genome was searched to identify linkage loci to autoimmune phenotypes inherited from a lupus MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice, which exhibits glomerulonephritis, splenomegaly and antinuclear autoantibody. The genome-wide association study confirmed four linkage loci on chromosomes 4, 7, 13, and 17. Furthermore, differential analyses performed using male and female groups of MBN2 mice revealed that two loci located on chromosomes 4 (41-72 cM, MRL/lpr allele) and 7 (4-21 cM, B6/lpr allele) were male specific and suppressed autoimmune phenotypes. Notably, the sum effect of the two loci adequately explained a range of SrD developed in the MBN2 mice. Our present findings suggest the presence of a male-predominant mechanism underlying the development of SrD in autoimmunity, depending on the effects of autosomal loci under an undefined male-specific condition.

CD19 hyperexpression augments Sle1-induced humoral autoimmunity but not clinical nephritis

OBJECTIVE

B cell hyperactivity is a common denominator in murine and human systemic lupus erythematosus. Some susceptibility genes in lupus are associated with B cell hyperactivity, but others are clearly not. While the Sle1 lupus susceptibility locus of NZM2410/NZW origin leads to chromatin-focused autoimmunity, genetically engineered overexpression of CD19 leads to "generalized" B cell hyperactivity. We undertook this study to determine the degree to which generalized B cell hyperactivity can amplify lupus pathogenesis.

METHODS

To elucidate the impact of generalized B cell hyperactivity on Sle1-triggered autoimmunity, B6 mice bearing the human CD19 transgene were rendered congenic for the Sle1(z) genetic locus and phenotyped for serologic, cellular, and pathologic evidence of lupus.

RESULTS

As expected, B6.Sle1.hCD19(Tg/Tg) mice, homozygous at Sle1 and bearing the hCD19 transgene, exhibited high levels of IgM and IgG anti-DNA/antiglomerular autoantibodies, skewed B cell subsets, and profoundly activated B and T cells. Despite exhibiting glomerular IgM, IgG, and complement deposits, these mice did not exhibit accelerated mortality or any clinical evidence of renal dysfunction.

CONCLUSION

Generalized B cell hyperactivity may augment humoral autoimmunity, but this may not suffice to engender end-organ disease in lupus. These findings allude to the presence of an additional distal checkpoint that dissociates pathogenic autoantibody formation and renal immunoglobulin deposition from the progression to clinical nephritis in lupus.

Genetic basis of murine lupus nephritis

Systemic lupus erythematosus is a generalized autoimmune disease affecting multiple end-organs including the kidneys. Glomerulonephritis is a leading cause of death in lupus, both in patients and murine models that develop disease spontaneously. Genetic mapping studies have uncovered several genetic intervals that confer susceptibility to nephritis both in human beings and in mice. This review surveys the genomic positions of these nephritis susceptibility loci in murine lupus. Currently we know very little about the molecular identities of the culprit genes within these mapped loci and whether these genetic elements contribute to nephritis directly in a renal-intrinsic fashion or indirectly by augmenting the formation of pathogenic autoantibodies. The next decade is likely to witness a significant broadening of our understanding of how different genes and molecules might facilitate end-organ damage in lupus.

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.

Hypertension and impaired vascular function in a female mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease that predominantly affects women during their reproductive years. Although women with SLE have hypertension, the underlying mechanisms for this have not been examined. Despite the fact that inflammation is associated with altered endothelial and vascular function, the role of altered vascular function in the development of hypertension during SLE is unclear. In the present study, we tested whether a mouse model of SLE (NZBWF1) develops hypertension and examined whether increased blood pressure was associated with impaired endothelial-dependent relaxation. Female NZBWF1 mice were studied at 8, 20, and 36 wk of age. By 36 wk, urinary albumin and antinuclear antibodies were increased in SLE compared with control mice. Mean arterial pressure, measured by radiotelemetry, was significantly increased in SLE mice (124 ± 4 mmHg, n = 10) compared with control NZW/LacJ mice (111 ± 3 mmHg, n = 7) at 36 wk. Isolated carotid arteries from NZBWF1 mice, precontracted with U-46619 for assessment of endothelial-dependent relaxation, demonstrated a progressively impaired relaxation to ACh with age, although endothelial nitric oxide synthase mRNA expression was not different. Maximal tension generated by 5-hydroxytryptamine was increased in carotid arteries from NZBWF1 mice compared with controls at 8, 20, and 36 wk of age, suggesting a role for altered vascular function early on in the progression of SLE. Taken together, our data support a role for altered endothelial function as a contributing factor to the development of hypertension during SLE.

Systemic lupus erythematosus: multiple immunological phenotypes in a complex genetic disease

Systemic lupus erythematosus (SLE) is a complex polygenic autoimmune disease characterized by the presence of anti-nuclear autoantibodies (ANAs) that are often detectable years prior to the onset of clinical disease. The disease is associated with a chronic activation of the immune system, with the most severe forms progressing to inflammatory damage that can impact multiple organ systems in afflicted individuals. Current therapeutic strategies poorly control disease manifestations and are generally immunosuppressive. Recent studies in human patient populations and animal models have associated elements of the innate immune system and abnormalities in the immature B lymphocyte receptor repertoires with disease initiation. A variety of cytokines, most notably type I interferons, play important roles in disease pathogenesis and effector mechanisms. The genetic basis for disease susceptibility is complex, and analyses in humans and mice have identified multiple susceptibility loci, several of which are located in genomic regions that are syntenic between humans and mice. The complexities of the genetic interactions that mediate lupus have been investigated in murine model systems by characterizing the progressive development of disease in strains expressing various combinations of susceptibility alleles. These analyses indicate that genetic epistasis dramatically impact disease development and support the feasibility of identifying molecular pathways that can suppress disease progression without completely impairing normal immune function.

Current topics in human SLE genetics

Susceptibility to systemic lupus erythematosus (SLE) depends on genetic and environmental factors. Genome scan studies have identified eight chromosomal regions with significant linkage to SLE that are confirmed by individual cohorts, suggesting that susceptibility genes may be identified within each of these loci. Linkage studies and single nucleotide polymorphisms (SNPs) have led to the identification of positional candidate genes, and their functional allelic variants have demonstrated molecular pathogenesis of the disease. The discovery of positional candidate genes that are associated with various autoimmune diseases signifies a common pathway in the mechanism of these diseases. Copy polymorphisms in susceptibility genes provide evidence in how genetic plasticity affects complex phenotypes as seen in SLE.

Genetic Dissection of Vasculitis, Myeloperoxidase-Specific Antineutrophil Cytoplasmic Autoantibody Production, and Related Traits in Spontaneous Crescentic Glomerulonephritis-Forming/Kinjoh Mice

The spontaneous crescentic glomerulonephritis-forming/Kinjoh (SCG/Kj) mouse is a model of human crescentic glomerulonephritis and vasculitis associated with the production of the myeloperoxidase (MPO)-specific antineutrophil cytoplasmic autoantibody (MPO-ANCA). Although the disease is mediated initially by mutation of the Fas gene (lpr), SCG/Kj mice also have non-Fas predisposing genetic factors. To define these factors, genome-wide quantitative trait locus (QTL) mapping was performed on female (B(6)x SCG/Kj) F(2) intercross mice. Fourteen non-Fas QTLs were identified. QTLs of glomerulonephritis were located on chromosomes 1, 10, 13, 16, and 17, vasculitis on chromosomes 1 and 17, splenomegaly on chromosome 1, hypergammaglobulinemia on chromosomes 1, 2, 4, 6, 7, 11, 13, and 17, antinuclear Ab on chromosomes 1, 8, 10, and 12, and MPO-ANCA production on chromosomes 1 and 10. Significant QTLs derived from SCG/Kj on chromosomes 1, 2, 7, and 13 were designated Scg-1 to Scg-5, respectively, and those derived from B(6) on chromosomes 4, 6, 17, and 10 were designated Sxb-1 to Sxb-4, respectively. Two loci linked to MPO-ANCA production on chromosomes 1 and 10 were designated Man-1 and Man-2 (for MPO-ANCA), respectively. Although both Scg-1 and Scg-2 were on chromosome 1 and shared several functions, it was of interest that aberrant MPO-ANCA production was exclusively controlled by Man-1, the centromeric half region of the Scg-2 chromosomal segment. We also examined the epistatic effects between the lpr mutation and non-Fas susceptibility genes. QTLs are discussed in relation to previously described loci, with emphasis on their candidate genes.

Genes mediating environment interactions in type 1 diabetes

The relative risk of type 1 (autoimmune) diabetes mellitus for a sibling of an affected patient is fifteen times that of the general population, indicating a strong genetic contribution to the disease. Yet, the incidence of diabetes in most Western communities has doubled every fifteen years since the Second World War - a rate of increase that can only possibly be explained by a major etiological effect of environment. Here, the authors provide a selective review of risk factors identified to date. Recent reports of linkage of type 1 diabetes to genes encoding pathogen pattern recognition molecules, such as toll-like receptors, are discussed, providing a testable hypothesis regarding a mechanism by which genetic and environmental influences on disease progress are integrated.

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.

The genetics of systemic lupus erythematosus

For years the identification of candidate genes has been approached in various ways. The latest technology allows for whole genome SNP analysis in genetic association studies. These studies pose new challenges but also new possibilities. I hereby review what is known to date on lupus genetics and what challenges we are to overcome with the new available methods.

CTLA-4 (CD152) and its involvement in autoimmune disease

Autoimmune diseases (AID) are inherited as complex genetic diseases. Different Autoimmune diseases have been found to cluster in families and are believed to share some common etiological factors. With the exception of major histocompatibility complex (MHC) genes contributing susceptibility to these diseases have been difficult to identify. CD152 has emerged as one such candidate unifying several autoimmune diseases. We here review the evidence that CD152 constitutes a general susceptibility factor for multiple autoimmune diseases and discuss how CD152 and other co-stimulatory pathways may contribute to autoimmune pathogenesis.

Epistatic suppression of systemic lupus erythematosus: fine mapping of Sles1 to less than 1 mb

Sle is a susceptibility locus for systemic autoimmunity derived from the lupus-prone NZM2410 mouse. The New Zealand White-derived suppressive modifier Sles1 was identified as a specific modifier of Sle1 and prevents the development of IgG anti-chromatin autoantibodies mediated by Sle1 on the C57BL/6 (B6) background. Fine mapping of Sles1 with truncated congenic intervals localizes it to a approximately 956-kb segment of mouse chromosome 17. Sles1 completely abrogates the development of activated T and B cell populations in B6.Sle1. Despite this suppression of the Sle1-mediated cell surface activation phenotypes, B6.Sle1 Sles1 splenic B cells still exhibit intrinsic ERK phosphorylation. Classic genetic complementation tests using the nonautoimmmune 129/SvJ mouse suggests that this strain possesses a Sles1 allele complementary to that of New Zealand White, as evidenced by the lack of glomerulonephritis, splenomegaly, and antinuclear autoantibody production seen in (129 x B6.Sle1 Sles1)F(1)s. These findings localize and characterize the suppressive properties of Sles1 and implicate 129 as a useful strain for aiding in the identification of this elusive epistatic modifier gene.

Genetics of lupus nephritis

Susceptibility to lupus nephritis is the end-result of complex interactions between polymorphic genetic factors involved in the regulation of immune responses. In humans, genome-wide screens and candidate-gene analyses led to the identification of several loci containing potential targets (FcgammaRIIa, PTPN22, PD-1, IL-10) for physiopathological research and therapeutic interventions. In mice, the generation of congenic mice, bearing in a normal genetic background one single disease-associated locus, greatly improved our understanding of the mechanisms mediating the genetic contribution to the disease. In the future, the identification of disease-associated genes will open new perspectives for the development of more targeted therapies of lupus nephritis.

Hormonal modulation of B cell development and repertoire selection

Systemic lupus erythematosus is an autoimmune disorder characterized by the production of pathogenic autoantibodies, primarily to nuclear antigens. The etiology of SLE is not entirely understood, but it is well-appreciated that multiple factors such as genetics and environment contribute to disease progression and pathogenesis. There is also convincing evidence that gender plays an import role in SLE since the incidence of disease occurs with a female to male ratio of 9:1. While it is plausible that some sex-linked genes may contribute to the genetic predisposition for the disease, other likely culprits for this gender bias are the sex hormones estrogen and prolactin. The data implicating estrogen and prolactin in SLE, until recently, were largely circumstantial. However, within the last few years, data collected from both human and mouse studies have provided compelling evidence that alterations in sex hormone levels can alter tolerance of autoreactive B cells and exacerbate disease. In this review, we will discuss recent data demonstrating a role for estrogen and prolactin in SLE and the effect of these hormones on B cell maturation, selection and activation.

Autoimmune alterations induced by the New Zealand Black Lbw2 locus 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.

The effects of vitamin E supplementation on autoimmune-prone New Zealand black x New Zealand white F1 mice fed an oxidised oil diet

The purpose of the present study was to investigate the effect of vitamin E supplementation on autoimmune disease in New Zealand blackxNew Zealand white F1 (NZB/W F1) female mice fed an oxidised oil diet. First, 5-month-old mice were fed an AIN-76 diet containing either 150 g fresh soyabean oil/kg (15S), 50 g fresh soyabean oil/kg + 100 g oxidised frying oil/kg (5S10F) or 5S10F supplemented with all-rac-alpha-tocopheryl acetate at 275 mg/kg diet level (5S10F5E) or 550 mg/kg (5S10F10E), respectively, in experiment 1. The results showed that mice fed the 5S10F10E diet had a lower anti-double-stranded DNA IgG antibody level and a longer lifespan than those fed the 15S and 5S10F diets. Therefore, the 5S10F and 5S10F10E treatments were repeated in experiment 2 for further analysis. The results showed that vitamin E supplementation in the oxidised oil significantly decreased thiobarbituric acid-reactive substance values in the kidney and spleen of NZB/W F1 mice. Interferon-gamma and IL-6 production by mitogen-stimulated splenocytes decreased in mice fed the 5S10F10E diet, whereas the secretion of IL-2 and IL-10 was not affected. The percentage of T-cells was significantly higher and that of MHC class II-bearing cells was lower in the spleens of the 5S10F10E group. The 5S10F10E group had a significantly higher linoleic acid (18 : 2n-6) composition than the 5S10F diet group. Therefore, vitamin E supplementation in oxidised oil might decrease oxidative stress, anti-double-stranded DNA IgG antibody, regulate cytokines and lymphocyte subsets, and subsequently alleviate the severity of autoimmune disease such as systemic lupus erythematosus under oxidative stress.

Genetic origin of lupus in NZB/SWR hybrids: Lessons from an intercross study

OBJECTIVE

(SWR x NZB)F(1) (or SNF(1)) hybrid mice succumb to lupus nephritis. A previous analysis of SNF(1) x NZB backcross mice revealed the existence of 4 SWR loci (H2 on chromosome 17, Swrl-1 on chromosome 1, Swrl-2 on chromosome 14, and Swrl-3 on chromosome 18) and 2 NZB loci (Nba1 and Lbw2/Sbw2, both on chromosome 4). A second study focusing on SNF(1) x SWR backcross offspring uncovered 5 suggestive loci for antinuclear antibody formation, consisting of 3 dominant NZB contributions (Nba4 on chromosome 5, Lbw4 on chromosome 6, and Nba5 on chromosome 7) and 2 recessive SWR contributions (Swrl-1 on chromosome 1 and Swrl-4 on chromosome 10). The present intercross study was executed to replicate the earlier findings, using an independent panel of (SWR x NZB)F(2) offspring.

METHODS

A panel of (NZB x SWR)F(2) hybrids were phenotyped (for renal disease, early mortality, and a variety of autoantibodies) and genotyped (using 95 microsatellite primers positioned across all 19 autosomes and the X chromosome). Linkage analysis was conducted using the derived phenotype and genotype data, with the interval-mapping program MapManager.

RESULTS

Four suggestive loci were mapped: Swrl-5 on chromosome 1 (peak at 106 cM), linked to hypergammaglobulinemia; an NZB locus on chromosome 5 (Nba4; peak at 15 cM), linked to IgG anti-single-stranded DNA (anti-ssDNA) antibodies, IgG anti-doubled-stranded DNA (anti-dsDNA) antibodies, and glomerulonephritis; an NZB locus on chromosome 13 (Nba6; peak at 28 cM), linked to IgG anti-dsDNA antibodies; and an SWR locus on chromosome 14 (Swrl-2; peak at 30 cM), linked to IgG anti-ssDNA antibodies. Eight additional loci revealed linkage at P < 0.01, of which 7 co-mapped with lupus susceptibility loci previously identified in other models.

CONCLUSION

Considering all 3 mapping studies together, lupus in SWR/NZB hybrids appears to be the epistatic end product of several distinct loci, of which 3 SWR-derived loci (Swrl-1, Swrl-2, and Swrl-3) and 5 NZB-derived loci (Nba1, Nba3, Nba4, Nba5, and Lbw4) have been independently confirmed. The immunologic functions and molecular identities of these loci await elucidation.

Multiple loci are linked with anti-red blood cell antibody production in NZB mice -- comparison with other phenotypes implies complex modes of action

The New Zealand Black (NZB) mouse strain is a model of autoimmune haemolytic anaemia (AHA) and systemic lupus erythematosus (SLE), characterized by the production of anti-red blood cell (RBC) antibodies and anti-nuclear antibodies (ANA), respectively. A linkage analysis was carried out in an (NZB x BALB/c) F(2) cross in order to identify loci involved in the production of both anti-RBC IgM and IgG antibodies. These regions of linkage were compared with linkage data to ANA from the same cohort and other linkage analyses involving New Zealand mice. Four previously described NZB loci linked to anti-RBC antibodies were confirmed, and eight novel loci linked to this trait were also mapped: five of which were of NZB origin, and three derived from the non-autoimmune BALB/c background. A comparison between loci linked with anti-RBC antibodies and ANA demonstrated many that co-localize, suggesting the presence of genes that result in the general breaking of tolerance to self-antigen. Furthermore, the observation that some loci were associated only with the anti-RBC response suggests an antigen specific mechanism in addition to a general breaking of tolerance. A locus linked with anti-RBC antibodies and ANA on distal chromosome 7 in this cohort is orthologous to one on the q arm of human chromosome 11, a region linked to AHA and ANA in human SLE.

Genetic basis of murine lupus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the formation of a variety of autoantibodies and subsequent development of severe glomerulonephritis. Etiology of SLE remains unknown even if it is now well established that SLE is under polygenic control as well as the contribution of hormonal and environmental factors. The availability of several murine strains that spontaneously develop an autoimmune syndrome resembling human SLE, such as New Zealand, MRL and BXSB mice has provided useful tools for the genetic dissection of susceptibility to SLE. Moreover, development of various transgenic and mutant mice has made it possible to identify a number of susceptibility genes such as those involved in the regulation of apoptosis or B cell receptor signaling that can trigger lupus-like phenotypes. Obviously, further identification of the genetic defects present in lupus-prone mice is of paramount importance for understanding the immunopathogenesis of SLE.

The candidate gene approach: have murine models informed the study of human SLE?

Genome wide linkage studies in human SLE have identified seven highly significant loci linked to SLE, and more than 20 other loci showing suggestive linkage to disease. However, pin-pointing the susceptibility alleles in candidate genes within these linkage regions is challenging, due the genetic heterogeneity, racial differences and environmental influences on disease aetiology. Utilization of murine models of spontaneous lupus nephritis provide a complementary approach, which may then identify candidate genes for analysis in human cases. This review highlights the utility of cross-species approach to identify and characterize the effect of given candidate genes in lupus. The examples described in this review demonstrate the importance of bringing together both genetic and functional information in human and mouse studies.

New loci from New Zealand Black and New Zealand White mice on chromosomes 4 and 12 contribute to lupus-like disease in the context of BALB/c

New Zealand Black (NZB) and New Zealand White (NZW) mice are genetically predisposed to a lupus-like autoimmune syndrome. To further define the loci linked to disease traits in NZB and NZW mice in the context of the BALB/c genetic background, linkage analyses were conducted in two crosses: (NZW x BALB/c.H2(z))F(1) x NZB and (NZB x BALB/c)F(2). Novel loci linked to autoantibody production and glomerulonephritis, present in both NZB and NZW mice, were identified on proximal chromosomes 12 and 4. The chromosome 12 locus showed the strongest linkage to anti-nuclear Ab production. Additionally, a number of other novel loci linked to lupus traits derived from both the New Zealand and non-autoimmune BALB/c genomes were identified. Furthermore, we confirm the linkage of disease to a number of previously described lupus-associated loci, demonstrating that they are relatively background independent. These data provide a number of additional candidate gene regions in murine lupus, and highlight the powerful effect the non-autoimmune background strain has in influencing the genetic loci linked to disease.

Genetic control of NKT cell numbers

NKT cells play a critical role in shaping the character and strength of a wide range of immune responses, including those against pathogens, tumours, allografts and autologous tissues. Because numbers of NKT cells affect clinical outcomes in a wide range of disease models, and this characteristic demonstrates allelic variation, the mapping of the locations and identification of the coding sequences of these genes has become a matter of significant importance. Here, we review the results to date that examine the effects of targeted deletion of a number of candidate genes, as well as the congenic and genetic linkage analyses that have attempted to localize allelic loci that affect NKT cell numbers. Although a number of candidate genes have been examined, there is no evidence that any of these contribute to variation in NKT cell numbers in natural populations. Two of the most important genetic regions controlling NKT cell numbers are Nkt1 on chromosome 1, which may contribute to lupus susceptibility, and Nkt2 on chromosome 2, which appears to contribute to diabetes susceptibility. Of great interest is a third locus on chromosome 18, identified in a novel congenic line, which can confer an absolute deficiency in this important immunoregulatory lymphocyte population.

Genetic Complementation in Female (BXSB × NZW)F2 Mice

F(1) hybrids among New Zealand Black (NZB), New Zealand White (NZW), and BXSB lupus-prone strains develop accelerated autoimmunity in both sexes regardless of the specific combination. To identify BXSB susceptibility loci in the absence of the Y chromosome accelerator of autoimmunity (Yaa) and to study the genetics of this complementation, genome-wide quantitative trait locus (QTL) mapping was performed on female (BXSB x NZW)F(2) mice. Six QTL were identified on chromosomes 1, 4, 5, 6, 7, and 17. Survival mapped to chromosomes 5 and 17, anti-chromatin Ab to chromosomes 4 and 17, glomerulonephritis to chromosomes 6 and 17, and splenomegaly to chromosomes 1, 7, and 17. QTL on chromosomes 4 and 6 were new and designated as Lxw1 and -2, respectively. Two non-MHC QTL (chromosomes 1 and 4) were inherited from the BXSB and the rest were NZW-derived, including two similar to previously defined loci. Only two of 11 previously defined non-MHC BXSB QTL using male (Yaa(+)) crosses were implicated, suggesting that some male-defined BXSB QTL may require coexpression of the Yaa. Findings from this and other studies indicate that BXSB and NZB backgrounds contribute completely different sets of genes to complement NZW mice. Identification of susceptibility genes and complementing genes in several lupus-prone strain combinations will be important for defining the epistatic effects and background influences on the heterogeneous genetic factors responsible for lupus induction.

Genetic control of NKT cell numbers maps to major diabetes and lupus loci

Natural killer T cells are an immunoregulatory population of lymphocytes that plays a critical role in controlling the adaptive immune system and contributes to the regulation of autoimmune responses. We have previously reported deficiencies in the numbers and function of NKT cells in the nonobese diabetic (NOD) mouse strain, a well-validated model of type 1 diabetes and systemic lupus erythematosus. In this study, we report the results of a genetic linkage analysis of the genes controlling NKT cell numbers in a first backcross (BC1) from C57BL/6 to NOD.Nkrp1(b) mice. The numbers of thymic NKT cells of 320 BC1 mice were determined by fluorescence-activated cell analysis using anti-TCR Ab and CD1/alpha-galactosylceramide tetramer. Tail DNA of 138 female BC1 mice was analyzed for PCR product length polymorphisms at 181 simple sequence repeats, providing greater than 90% coverage of the autosomal genome with an average marker separation of 8 cM. Two loci exhibiting significant linkage to NKT cell numbers were identified; the most significant (Nkt1) was on distal chromosome 1, in the same region as the NOD mouse lupus susceptibility gene Babs2/Bana3. The second most significant locus (Nkt2) mapped to the same region as Idd13, a NOD-derived diabetes susceptibility gene on chromosome 2.

Functional dissection of lupus susceptibility loci on the New Zealand black mouse chromosome 1: evidence for independent genetic loci affecting T and B cell activation

In previous work, we demonstrated linkage between a broad region on New Zealand Black (NZB) chromosome 1 and increased costimulatory molecule expression on B cells and autoantibody production. In this study, we produced C57BL/6 congenic mice with homozygous NZB chromosome 1 intervals of differing lengths. We show that both B6.NZBc1(35-106) (numbers denote chromosomal interval length) and B6.NZBc1(85-106) mice produce IgG anti-nuclear autoantibodies, but B6.NZBc1(35-106) mice develop significantly higher titers of autoantibodies and more severe renal disease than B6.NZBc1(85-106) mice. Cellular analysis of B6.NZBc1(85-106) mice revealed splenomegaly and increased numbers of memory T cells. In addition to these features, B6.NZBc1(35-106) mice had altered B and T cell activation with increased expression of CD69, and for B cells, costimulatory molecules and MHC. Introduction of an anti-hen egg white lysozyme Ig transgene, as a representative nonself-reactive Ig receptor, onto the B6.NZBc1(35-106) background corrected the B cell activation phenotype and led to dramatic normalization of splenomegaly and T cell activation, but had little impact on the increased proportion of memory T cells. These findings indicate that there are multiple lupus susceptibility genes on NZB chromosome 1, and that although B cell defects play an important role in lupus pathogenesis in these mice, they act in concert with T cell activation defects.

Genetic heterogeneity of autoimmune disorders in the nonobese diabetic mouse

The nonobese diabetic mouse is highly susceptible not only to diabetes but to several autoimmune diseases, and one might suspect that these are controlled by a shared set of genes. However, based on various gene-segregation experiments, it seems that only a few loci are shared and that each disorder is influenced also by a unique set of genes.

A genetic analysis of lupus

Systemic lupus erythematosus (SLE) is a complex multigenic inherited disease with susceptibility determined by a combination of genetic, environmental and stochastic factors. Although not yet defined, recent technical advances have provided the means to dissect the component genetic contributions of polygenic traits. We have applied such approaches to mouse models of spontaneous SLE and, in this report, summarize our genome wide mapping studies that identified loci predisposing to several major lupus-related traits. Through the generation and study of interval congenic lines, precise mapping, and screening of candidate genes, identification of the specific genes and mechanisms associated with some of the major loci is currently being pursued.

Dominant NZB contributions to lupus in the (SWR x NZB)F1 model

(SWR x NZB)F1 (or SNF1) mice succumb to lupus nephritis. Analysis of NZB x SNF1 backcross mice has recently revealed the existence of four dominant SWR loci (H2 on Chr 17, Swrl-1 on Chr 1, Swrl-2 on Chr 14 and Swrl-3 on Chr 18), and two NZB loci (Nba1 and Lbw2/Sbw2, both on Chr 4) conferring lupus susceptibility. The present study focusing on a panel of 88 SWR x SNF1 backcross mice reveals the existence of five suggestive loci for antinuclear antibody formation, consisting of three dominant NZB contributions (Nba4 on Chr 5, Lbw4 on Chr 6, and Nba5 on Chr 7), and two recessive SWR contributions (Swrl-1 on Chr 1, and Swrl-4 on Chr 10). In addition, this study reveals a dominant NZB locus for GN (Nba3 on Chr 7, peak at 31 cM), and a dominant NZB locus linked to early mortality, on Chr 10 (peak at 4 cM). Collectively, these studies suggest that lupus in the SNF1 strain is the epistatic end-product of four dominant SWR loci and four dominant NZB loci. The immunological functions and molecular identities of these loci await elucidation.

The genetics of systemic lupus erythematosus: putting the pieces together

With lambda(s) estimates of 10 to 20 and other evidence of familial aggregation, as well as a monozygotic twin concordance rate >20, systemic lupus erythematosus (SLE) would appear to be a very promising phenotype using modern genetic approaches. Indeed, genetic associations are already known at numerous candidate loci including various HLA alleles, complement component genes, Fcgamma receptors, and others, and murine genetic studies of lupus models have provided additional candidate genes and potential syntenic linkages to evaluate in man. The completed genetic linkage studies performed on various collections of pedigrees multiplex for SLE have identified 60 susceptibility loci with varying degrees of evidence for linkage in man. Seven of these meet or exceed the threshold for significant linkage (LOD > or = 3.3 or P < or = 0.00005) at 1q22-23, 1q41, 2q37, 4p16, 6p21-11, 16q13 and 17p13. In addition, these linkages usually dominate in one ethnicity or another, suggesting that the responsible polymorphisms, once identified, will also vary by ethnicity. Evidence that these linkages can be reproduced range from outright independent confirmation (1q41, 4p16 and 6p21) to additional suggestive evidence in the genomic region of the purported linkage (1q22-23 and 2q37). The results now available suggest that human lupus genetics are robust and that gene identification should be possible using existing genetic approaches and technologies.

Evidence for a susceptibility gene (SLEH1) on chromosome 11q14 for systemic lupus erythematosus (SLE) families with hemolytic anemia

Hemolytic anemia is a forme fruste of systemic lupus erythematosus (SLE), being observed months or even years before the onset of other clinical manifestations in some patients. We hypothesized that hemolytic anemia in those SLE-affected patients would identify a group of SLE pedigrees that share a high degree of genetic homogeneity. From 160 multiplex SLE pedigrees, we sought evidence for linkage in 35 (16 African-American, 17 European-American, and 2 Hispanic) who had at least one SLE-affected patient with hemolytic anemia. Significant linkage was present at 11q14 in the 16 African-American pedigrees, yielding a maximum two-point logarithm of odds (LOD) score of 4.5 at D11S2002. The segregation pattern of SLE in these African-American pedigrees suggested a dominant mode of inheritance and, when maximized across penetrance and disease allele frequencies, produced a multipoint LOD of 4.7. Multipoint analysis yielded a multipoint heterogeneity LOD score of 3.6 (alpha = 0.63), again with maximum LOD at D11S2002. Finally, markers typed 7 centimorgans to either side of D11S2002 achieved LOD scores of 3 or better by using the maximized model, supporting linkage to 11q14. Clearly, pedigree ascertainment based on select clinical manifestations is an important tool, capable of revealing otherwise cryptic genetic linkages in complex genetic diseases. Thus, we show strong evidence for an SLE susceptibility gene, SLEH1, near D11S2002 in African-American pedigrees multiplex for SLE that have at least one SLE-affected patient with hemolytic anemia.

B cell stimulatory effects of alpha-enolase that is differentially expressed in NZB mouse B cells

Intrinsic polyclonal B cell activation is characteristic of NZB mice and it contributes to the development of lupus nephritis in NZB crosses. Although multiple autosomal genes appear to be involved, the major loci for B cell hyperactivity have been mapped on chromosome 4. To identify various genes determining B cell hyperactivity, differential mRNA display was done comparing B cells of NZB and BALB/c mice. The approach yielded 32 genes that were consistently upregulated in NZB B cells. Among these, alpha-enolase, which is located in the region of chromosome 4 containing B cell hyperactivity loci, was found to be spontaneously overexpressed only in NZB B cells, but not in splenic B or T cells of BALB/c or T cells of NZB mice. Exposure to soluble, but not plate-bound, enolase induced splenic B cells from normal BALB/c mice or B cell lymphoma lines to secrete Ig that was mediated by augmented transcription. Moreover, in combination with a subthreshold stimulus with anti-IgM, enolase augmented the expression of CD69 and B7.2 in nai;ve B cells from normal mice. Enolase probably functions intracellularly as an accessory molecule in stimulating B cells. Since functionally related genes tend to congregate, enolase may contribute to polyclonal B cell activation in cooperation with other genes in the hyperactivity loci, which appear to be in a transcriptionally active region in NZB B cells.

C1q regulatory region polymorphism down-regulating murine c1q protein levels with linkage to lupus nephritis

Much of the pathology of systemic lupus erythematosus (SLE) is caused by deposition of immune complexes (ICs) into various tissues, including renal glomeruli. Because clearance of ICs depends largely on early complement component C1q, homozygous C1q deficiency is a strong genetic risk factor in SLE, although it is rare in SLE patients overall. In this work we addressed the issue of whether genetic polymorphisms affecting C1q levels may predispose to SLE, using the (NZB x NZW)F(1) model. C1q genes are composed of three genes, C1qa, C1qc, and C1qb, arranged in this order, and each gene consists of two exons separated by one intron. Sequence analysis of the C1q gene in New Zealand Black (NZB), New Zealand White (NZW), and BALB/c mice showed no polymorphisms in exons and introns of three genes. However, Southern blot analysis revealed unique insertion polymorphism of a total of approximately 3.5 kb in the C1qa upstream region of NZB mice. C1q levels in sera and culture supernatants of LPS-stimulated peritoneal macrophages and C1q messages in spleen cells were all lower in disease-free young NZB and (NZB x NZW)F(1) mice than in age-matched non-autoimmune NZW and BALB/c mice. Quantitative trait loci analysis using (NZB x NZW)F(1) x NZW backcrosses showed that NZB microsatellites in the vicinity of the C1q allele on chromosome 4 were significantly linked to low serum C1q levels and the development of nephritis. These data imply that not only C1q deficiency but also regulatory region polymorphisms down-regulating C1q levels may confer the risk for lupus nephritis by reducing IC clearance and thus promoting IC deposition in glomeruli.

Genome screening for susceptibility loci in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex, multigenic autoimmune disease with a wide spectrum of clinical manifestations. Much of the pathology is attributed to deposition to various tissues of immune complexes continuously formed with autoantibodies; thus, the pathogenesis is related to dysregulation of self-reactive B cells. Recent family linkage studies and allele-sharing linkage analyses of affected sibling pairs have advanced genome screening for susceptibility loci in SLE, and a considerable number of chromosomal intervals with significant or suggestive linkage to SLE have been identified. However, there are still several inherent difficulties in precisely identifying loci and genes, as the complexity of polygenic inheritance of SLE phenotypes is considerable. One must note that each specific aspect of diverse SLE phenotypes (clinical manifestations and immunological abnormalities) is mostly controlled separately by a different set of susceptibility loci. Involvement of positive and negative epistatic gene interactions often puzzles genetic analyses. Studies on SLE using murine lupus models are ongoing to solve some of these difficulties. Comparative studies have identified several syntenic chromosomal intervals with susceptibility loci in both mouse models and humans. Thus, combining knowledge derived from both human and murine studies is vital. The ultimate identification of susceptibility genes and their functions will probably depend largely on studies using genetically manipulated mutant mice, including those with homologous recombination of potent polymorphic target genes. The up-coming completion of genomic sequences in mice and humans is predicted to limit the numbers of potent candidate genes in particular genomic intervals and accelerates this line of studies. Such knowledge will lead to elucidation of genetic and cellular mechanisms involved in the dysregulation of self-reactive lymphocytes in the pathogenesis of SLE. Prophylactic and therapeutic clinical approaches can then be better designed.

A novel susceptibility locus on chromosome 2 in the (New Zealand Black x New Zealand White)F1 hybrid mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is inherited as a complex polygenic trait. (New Zealand Black (NZB) x New Zealand White (NZW)) F(1) hybrid mice develop symptoms that remarkably resemble human SLE, but (NZB x PL/J)F(1) hybrids do not develop lupus. Our study was conducted using (NZW x PL/J)F(1) x NZB (BWP) mice to determine the effects of the PL/J and the NZW genome on disease. Forty-five percent of BWP female mice had significant proteinuria and 25% died before 12 mo of age compared with (NZB x NZW)F(1) mice in which >90% developed severe renal disease and died before 12 mo. The analysis of BWP mice revealed a novel locus (chi(2) = 25.0; p < 1 x 10(-6); log of likelihood = 6.6 for mortality) designated Wbw1 on chromosome 2, which apparently plays an important role in the development of the disease. We also observed that both H-2 class II (the u haplotype) and TNF-alpha (TNF(z) allele) appear to contribute to the disease. A suggestive linkage to proteinuria and death was found for an NZW allele (designated Wbw2) telomeric to the H-2 locus. The NZW allele that overlaps with the previously described locus Sle1c at the telomeric part of chromosome 1 was associated with antinuclear autoantibody production in the present study. Furthermore, the previously identified Sle and Lbw susceptibility loci were associated with an increased incidence of disease. Thus, multiple NZW alleles including the Wbw1 allele discovered in this study contribute to disease induction, in conjunction with the NZB genome, and the PL/J genome appears to be protective.

The NOD mouse as a model of SLE

In addition to developing a high incidence of type 1 diabetes caused by a specific autoimmune response against pancreatic beta cells in the islets of Langerhans, NOD mice also demonstrate spontaneous autoimmunity to other targets including the thymus, adrenal gland, salivary glands, thyroid, testis, nuclear components and red blood cells. Moreover, treatment of pre-diabetic NOD mice with an intravenous dose of heat killed Mycobacterium bovis (M. bovis; bacillus Calmette-Guèrin (BCG)) protects them from developing type 1 diabetes, but instead precipitates an autoimmune rheumatic disease similar to systemic lupus erythematosus (SLE), characterised by accelerated and increased incidence of haemolytic anaemia (HA), anti-nuclear autoantibody (ANA) production, exacerbation of sialadenitis, and the appearance of immune complex-mediated glomerulonephritis (GN). The reciprocal switching between the two phenotypes by a single environmental trigger (mycobacterial exposure) raised the possibility that genetic susceptibility for type 1 diabetes and SLE may be conferred by a single collection of genes in the NOD mouse. This review will focus on the genetic components predisposing NOD mice to SLE induced by BCG treatment and compare them to previously determined diabetes susceptibility genes in this strain and SLE susceptibility genes in the BXSB, MRL and the New Zealand mouse strains.