Linkage analysis of systemic lupus erythematosus induced in diabetes-prone nonobese diabetic mice by Mycobacterium bovis

Silicosis and Silica-Induced Autoimmunity in the Diversity Outbred Mouse

Epidemiological studies have confidently linked occupational crystalline silica exposure to autoimmunity, but pathogenic mechanisms and role of genetic predisposition remain poorly defined. Although studies of single inbred strains have yielded insights, understanding the relationships between lung pathology, silica-induced autoimmunity, and genetic predisposition will require examination of a broad spectrum of responses and susceptibilities. We defined the characteristics of silicosis and autoimmunity and their relationships using the genetically heterogeneous diversity outbred (DO) mouse population and determined the suitability of this model for investigating silica-induced autoimmunity. Clinically relevant lung and autoimmune phenotypes were assessed 12 weeks after a transoral dose of 0, 5, or 10 mg crystalline silica in large cohorts of DO mice. Data were further analyzed for correlations, hierarchical clustering, and sex effects. DO mice exhibited a wide range of responses to silica, including mild to severe silicosis and importantly silica-induced systemic autoimmunity. Strikingly, about half of PBS controls were anti-nuclear antibodies (ANA) positive, however, few had disease-associated specificities, whereas most ANAs in silica-exposed mice showed anti-ENA5 reactivity. Correlation and hierarchical clustering showed close association of silicosis, lung biomarkers, and anti-ENA5, while other autoimmune characteristics, such as ANA and glomerulonephritis, clustered separately. Silica-exposed males had more lung inflammation, bronchoalveolar lavage fluid cells, IL-6, and autoantibodies. DO mice are susceptible to both silicosis and silica-induced autoimmunity and show substantial individual variations reflecting their genetic diverseness and the importance of predisposition particularly for autoimmunity. This model provides a new tool for deciphering the relationship between silica exposure, genes, and disease.

Dysregulation of T lymphocyte proliferative responses in autoimmunity

T cells are critically dependent on cellular proliferation in order to carry out their effector functions. Autoimmune strains are commonly thought to have uncontrolled T cell proliferation; however, in the murine model of autoimmune diabetes, hypo-proliferation of T cells leading to defective AICD was previously uncovered. We now determine whether lupus prone murine strains are similarly hyporesponsive. Upon extensive characterization of T lymphocyte activation, we have observed a common feature of CD4 T cell activation shared among three autoimmune strains-NOD, MRL, and NZBxNZW F1s. When stimulated with a polyclonal mitogen, CD4 T cells demonstrate arrested cell division and diminished dose responsiveness as compared to the non-autoimmune strain C57BL/6, a phenotype we further traced to a reliance on B cell mediated costimulation, which underscores the success of B cell directed immune therapies in preventing T cell mediated tissue injury. In turn, the diminished proliferative capacity of these CD4 T cells lead to a decreased, but activation appropriate, susceptibility to activation induced cell death. A similar decrement in stimulation response was observed in the CD8 compartment of NOD mice; NOD CD8 T cells were distinguished from lupus prone strains by a diminished dose-responsiveness to anti-CD3 mediated stimulation. This distinction may explain the differential pathogenetic pathways activated in diabetes and lupus prone murine strains.

Role for MyD88, TLR2 and TLR9 but not TLR1, TLR4 or TLR6 in experimental autoimmune encephalomyelitis

The potential roles of TLRs in the cause and pathogenesis of autoimmune CNS inflammation remain contentious. In this study, we examined the effects of targeted deletions of TLR1, TLR2, TLR4, TLR6, TLR9, and MyD88 on the induction of myelin oligodendrocyte glycoprotein 35-55 (MOG(35-55)) peptide/CFA/pertussis toxin-induced autoimmune encephalomyelitis. Although C57BL/6.Tlr1(-/-), C57BL/6.Tlr4(-/-) and C57BL/6.Tlr6(-/-) mice showed normal susceptibility to disease, signs were alleviated in female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice and C57BL/6.Tlr2/9(-/-) mice of both sexes. C57BL/6.Myd88(-/-) mice were completely protected. Lower clinical scores were associated with reduced leukocyte infiltrates. These results were confirmed by passive adoptive transfer of disease into female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice, where protection in the absence of TLR2 was associated with fewer infiltrating CD4(+) cells in the CNS, reduced prevalence of detectable circulating IL-6, and increased proportions of central (CD62L(+)) CD4(+)CD25(+)Foxp3(+) regulatory T cells. These results provide a potential molecular mechanism for the observed effects of TLR signaling on the severity of autoimmune CNS inflammation.

Allelic variation of Ets1 does not contribute to NK and NKT cell deficiencies in type 1 diabetes susceptible NOD mice

The NOD mouse is a well characterized model of type 1 diabetes that shares several of the characteristics of Ets1-deficient targeted mutant mice, viz: defects in TCR allelic exclusion, susceptibility to a lupus like disease characterized by IgM and IgG autoantibodies and immune complex-mediated glomerulonephritis, and deficiencies of NK and NKT cells. Here, we sought evidence for allelic variation of Ets1 in mice contributing to the NK and NKT cell phenotypes of the NOD strain. ETS1 expression in NK and NKT cells was reduced in NOD mice, compared to C57BL/6 mice. Although NKT cells numbers were significantly correlated with ETS1 expression in both strains, NKT cell numbers were not linked to the Ets1 gene in a first backcross from NOD to C57BL/6 mice. These results indicate that allelic variation of Ets1 did not contribute to variation in NKT cell numbers in these mice. It remains possible that a third factor not linked to the Ets1 locus controls both ETS1 expression and subsequently NK and NKT cell phenotypes.

Clinical application of NKT cell biology in type I (autoimmune) diabetes mellitus

Type 1 natural killer T (NKT) cells are a population of CD1d-restricted, regulatory T cells that exhibit various NK cell characteristics and rapidly produce cytokines on stimulation with glycolipid antigen. In type I diabetes (TID), NKT cells are thought to have a tolerogenic function, evidenced by NKT cell numerical and functional deficiencies in the nonobese diabetic (NOD) mouse, which when corrected, can ameliorate disease. The mechanisms by which NKT cells can mediate their immunosuppressive effects in NOD mice are still poorly understood, which makes successful clinical translation of NKT- cell-based therapies challenging. However, new insights into the genetic control of NKT cell deficiencies have provided some understanding of the genes that may control NKT cell number and function, potentially offering a new avenue for assessing TID risk in humans. Here, we review the mechanisms by which NKT cells are thought to prevent TID, discuss the evidence for involvement of NKT cells in the regulation of human TID and examine the genetic control of NKT cell number and function. A greater understanding of these areas will increase the chances of successful clinical manipulation of NKT cells to prevent or treat TID.

Congenic analysis of the NKT cell control gene Nkt2 implicates the peroxisomal protein Pxmp4

Type 1 NKT cells play a critical role in controlling the strength and character of adaptive and innate immune responses. We have previously reported deficiencies in the numbers and function of NKT cells in the NOD mouse strain, which is a well-validated model of type 1 diabetes and systemic lupus erythematosus. Genetic control of thymic NKT cell numbers was mapped to two linkage regions: Nkt1 on distal chromosome 1 and Nkt2 on chromosome 2. Herein, we report the production and characterization of a NOD.Nkrp1(b).Nkt2b(b) congenic mouse strain, which has increased thymic and peripheral NKT cells, a decreased incidence of type 1 diabetes, and enhanced cytokine responses in vivo and increased proliferative responses in vitro following challenge with alpha-galactosylceramide. The 19 highly differentially expressed candidate genes within the congenic region identified by microarray expression analyses included Pxmp4. This gene encodes a peroxisome-associated integral membrane protein whose only known binding partner is Pex19, an intracellular chaperone and component of the peroxisomal membrane insertion machinery encoded by a candidate for the NKT cell control gene Nkt1. These findings raise the possibility that peroxisomes play a role in modulating glycolipid availability for CD1d presentation, thereby influencing NKT cell function.

The genetics of immunoregulatory T cells

The immune repertoire of normal, healthy individuals contains autoreactive T cells and natural antibodies that, under normal conditions, are controlled, either through central tolerance or by the activity of immunoregulatory T cells to prevent the onset of autoimmune diseases. Over the years, several types of immunoregulatory T cells have been identified. These include natural CD4+CD25+Foxp3+T (Treg) cells and type 1 NKT cells, which develop in the thymus, as well as acquired immunoregulatory T cells, such as type 1 cells (Tr1), Th3 cells, Ts cells and anergic CD4 T cells, which all appear to be products of peripheral immune activation. While little is understood about the genetics of most types of immunoregulatory T cell, detailed information on the genetic control of NKT and Treg cells is now available and may contribute significantly to our understanding of the aetiology of autoimmune disease.

Two genetic loci independently confer susceptibility to autoimmune gastritis

Autoimmune gastritis is a CD4+ T cell-mediated disease induced in genetically susceptible mice by thymectomy on the third day after birth. Previous linkage analysis indicated that Gasa1 and Gasa2, the major susceptibility loci for gastritis, are located on mouse chromosome 4. Here we verified these linkage data by showing that BALB.B6 congenic mice, in which the distal approximately 40 Mb of chromosome 4 was replaced by C57BL/6 DNA, were resistant to autoimmune gastritis. Analysis of further BALB.B6 congenic strains demonstrated that Gasa1 and Gasa2 can act independently to cause full expression of susceptibility to autoimmune disease. Gasa1 and Gasa2 are located between D4Mit352-D4Mit204 and D4Mit343-telomere, respectively. Numerical differences in Foxp3+ regulatory T cells were apparent between the BALB/c and congenic strains, but it is unlikely that this phenotype accounted for differences in autoimmune susceptibility. The positions of Gasa1 and Gasa2 correspond closely to the positions of Idd11 and Idd9, two autoimmune diabetes susceptibility loci in nonobese diabetic (NOD), mice and this prompted us to examine autoimmune gastritis in NOD mice. After neonatal thymectomy, NOD mice developed autoimmune gastritis, albeit at a slightly lower incidence and severity of disease than in BALB/c mice. Diabetes-resistant congenic NOD.B6 mice, harbouring a B6-derived interval encompassing the Gasa1/2-Idd9/11 loci, demonstrated a slight reduction in the incidence of autoimmune gastritis. This reduction was not significant compared with the reduction observed in BALB.B6 congenic mice, suggesting a difference in the genetic aetiology of autoimmune gastritis in NOD and BALB mice.

Slamf1, the NKT Cell Control Gene Nkt1

Invariant NKT cells play a critical role in controlling the strength and character of adaptive immune responses. We have previously reported deficiencies in the numbers and function of NKT cells in the NOD mouse strain, which is a well-validated model of type 1 diabetes and systemic lupus erythematosus. Genetic control of thymic NKT cell numbers was mapped to two linkage regions: Nkt1 on distal chromosome 1 and Nkt2 on chromosome 2. In this study, we report the production and characterization of a NOD.Nkrp1(b).Nkt1(b) congenic mouse strain, apply microarray expression analyses to limit candidate genes within the 95% confidence region, identify Slamf1 (encoding signaling lymphocyte activation molecule) and Slamf6 (encoding Ly108) as potential candidates, and demonstrate retarded signaling lymphocyte activation molecule expression during T cell development of NOD mice, resulting in reduced expression at the CD4(+)CD8(+) stage, which is consistent with decreased NKT cell production and deranged tolerance induction in NOD mice.

Mouse bone marrow and peripheral blood erythroid cell counts are regulated by different autosomal genetic loci

Erythropoiesis is under fine control and genetic loci that affect it are likely to be important in a range of conditions. To assess the relative contributions of different genetic loci to parameters of erythropoiesis, we have measured RBC counts in the peripheral circulation and committed erythroid cells (RBC and small normoblasts) in the bone marrow in a cohort of (CBA/H x C57BL/6) F2 mice to map quantitative trait loci (QTL). Candidate genes were assessed using bioinformatics and DNA sequencing. Different autosomal loci affect bone marrow (chromosomes 5, 11 and 19) and peripheral blood (chromosome 4) erythroid cell counts but there may be a common chromosome X locus. Spleen weight QTL were found on chromosomes 3, 15 and 17. Surprisingly, erythropoietin (Epo) is the best candidate quantitative trait gene (QTG) in the chromosome 5 locus that affects bone marrow but not peripheral blood erythroid cell counts. Epo gene expression is known to be genetically regulated in mice, but our data suggest a tissue-specific role for epo in mouse erythropoiesis that is also genetically determined. The identity of the other QTG will be important both to further knowledge of the control of erythropoiesis and as potential modifier genes for haematological disorders.

Genetics of SLE in mice

Genetic studies in spontaneous, induced, and gene-manipulated mouse models of SLE have provided significant insights into the potential number and diversity of genes that can promote, resist, and modify lupus susceptibility. Novel genes and mechanisms of disease pathogenesis have also been identified. Importantly, mouse models have provided an initial view of the genomic landscape of lupus-affecting genes, and have documented the complexities of verifying and determining the role of specific candidate loci and genes. Mouse models of lupus should continue to serve as a vital approach to defining the genetics of SLE.

Phosphatidylserine exposure in B lymphocytes: a role for lipid packing

Plasma membrane lipids are usually distributed asymmetrically, with phosphatidylserine (PS) confined to the inner leaflet. PS exposure at the outer leaflet occurs early in apoptosis, but it is also constitutive on some nonapoptotic cell populations where it plays a role in cell signaling. How PS is transported (“flopped”) to the cell surface is unknown. Contrary to previous reports that normal murine B lymphocytes lack lipid asymmetry, we show that PS is normally restricted to the inner leaflet of these cells. PS exposure on normal B cells did, however, occur spontaneously ex vivo. Consistent with the hypothesis that loss of PS asymmetry is regulated by CD45, PS is constitutively exposed on viable, CD45-deficient B cells. We show that calcium-stimulated PS exposure in B cells is strain variable, ABCA1 independent, and both preceded by and dependent on a decrease in lipid packing. This decrease in lipid packing is concomitant with cell shrinkage and consequent membrane distortion, both of which are potently inhibited by blockers of volume-regulatory K+ and Cl- ion channels. Thus, changes in plasma membrane organization precede PS translocation. The data suggest a model in which PS redistribution may occur by a translocase-independent mechanism at energetically favorable sites of membrane perturbation where lipid packing is decreased.

Genetic and functional analysis of the Nkt1 locus using congenic NOD mice: improved Valpha14-NKT cell performance but failure to protect against type 1 diabetes

Defective invariant natural killer T-cells (iNKT cells) have been implicated in the etiology of type 1 diabetes in nonobese diabetic (NOD) mice. In a genome scan of a cross between NOD and C57BL/6 mice, the most significant locus controlling the number of iNKT cells, referred to as Nkt1, was recently mapped to distal chromosome 1. Here, using congenic mice for this chromosomal segment, we definitively demonstrate the existence of Nkt1 and show that introgression of the C57BL/6 allele onto the NOD background improves both the number of iNKT cells and their rapid production of cytokines elicited by alpha-galactosylceramide treatment, explaining at least half of the difference between the NOD and C57BL/6 strains. Using new subcongenic lines, we circumscribed the Nkt1 locus to a 8.7-cM segment, between the NR1i3 and D1Mit458 markers, that notably includes the SLAM (signaling lymphocytic activation molecule) gene cluster, recently involved in murine lupus susceptibility. However, despite a significant correction of the iNKT cell defect, the Nkt1 locus did not alter the course of spontaneous diabetes in congenic mice. Our findings indicate a complex relationship between iNKT cells and autoimmune susceptibility. Congenic lines nonetheless provide powerful models to dissect the biology of iNKT cells.

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.

Defective induction of CTLA-4 in the NOD mouse is controlled by the NOD allele of Idd3/IL-2 and a novel locus (Ctex) telomeric on chromosome 1

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), or CD152, is a negative regulator of T-cell activation and has been shown to be associated with autoimmune diseases. Previous work has demonstrated a defect in the expression of this molecule in nonobese diabetic (NOD) mice upon anti-CD3 stimulation in vitro. Using a genetic approach we here demonstrate that a novel locus (Ctex) telomeric on chromosome 1 together with the Idd3 (Il-2) gene confers optimal CTLA-4 expression upon CD3 activation of T-cells. Based on these data, we provide a model for how gene interaction between Idd3 (IL-2), Ctex, and Idd5.1 (Ctla-4) could confer susceptibility to autoimmune diabetes in the NOD mouse. Additionally, we showed that the Ctex and the Idd3 regions do not influence inducible T-cell costimulator (ICOS) protein expression in NOD mice. Instead, as previously shown, higher ICOS levels in NOD mice appear to be controlled by gene(s) in the Idd5.1 region, possibly a polymorphism in the Icos gene itself.

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.

Genetic Control of Autoimmunity: Protection from Diabetes, but Spontaneous Autoimmune Biliary Disease in a Nonobese Diabetic Congenic Strain

At least 20 insulin-dependent diabetes (Idd) loci modify the progression of autoimmune diabetes in the NOD mouse, an animal model of human type 1 diabetes. The NOD.c3c4 congenic mouse, which has multiple B6- and B10-derived Idd-resistant alleles on chromosomes 3 and 4, respectively, is completely protected from autoimmune diabetes. We demonstrate in this study, however, that NOD.c3c4 mice develop a novel spontaneous and fatal autoimmune polycystic biliary tract disease, with lymphocytic peribiliary infiltrates and autoantibodies. Strains having a subset of the Idd-resistant alleles present in the NOD.c3c4 strain show component phenotypes of the liver disease: NOD mice with B6 resistance alleles only on chromosome 3 have lymphocytic liver infiltration without autoantibody formation, while NOD mice with B10 resistance alleles only on chromosome 4 show autoantibody formation without liver infiltration. The liver disease is transferable to naive NOD.c3c4 recipients using splenocytes from affected NOD.c3c4 mice, demonstrating an autoimmune etiology. Thus, substitution of non-NOD genetic intervals into the NOD strain can prevent diabetes, but in turn cause an entirely different autoimmune syndrome, a finding consistent with a generalized failure of self-tolerance in the NOD genetic background. The complex clinical phenotypes in human autoimmune conditions may be similarly resolved into largely overlapping biochemical pathways that are then modified, potentially by alleles at a few key chromosomal regions, to produce specific autoimmune syndromes.

Cytokine dysregulation induced by apoptotic cells is a shared characteristic of macrophages from nonobese diabetic and systemic lupus erythematosus-prone mice

Macrophages from nonobese diabetic (NOD) mice, which spontaneously develop type I diabetes, share a defect in elicited cytokine production with macrophages from multiple diverse strains of systemic lupus erythematosus (SLE)-prone mice. We have previously shown that, in SLE-prone mice, this defect is triggered by exposure to apoptotic cells. We report in this work that macrophages from prediseased NOD mice also respond abnormally to apoptotic cells, mimicking closely the apoptotic cell-dependent abnormality that we have observed in multiple SLE-prone strains. This defect is characterized by the underexpression of IL-1 beta and multiple other cytokines. In the presence of apoptotic cells or FBS, elicited expression of IL-1 beta by NOD macrophages is markedly reduced compared with that by macrophages from control mice, including three strains of mice that develop type II (nonautoimmune) diabetes. Given the increasing role of apoptotic cells in tolerance and autoimmunity, a macrophage defect triggered by apoptotic cells has broad potential to upset the balance between tolerance and immunity. The concordance of this defect among so many diverse autoimmune-prone strains suggests that the genetic basis for this abnormality may constitute a permissive background for autoimmunity.

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 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.

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.

Mycobacteria, an environmental enhancer of lupus nephritis in a mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterized by the production of antibodies directed against self antigens. Immune complex glomerulonephritis (GN) is one of the most serious complications of this disorder and can lead to potentially fatal renal failure. The aetiology of SLE is complex and multifactorial, characterized by interacting environmental and genetic factors. Here we examine the nature of the renal pathology in mycobacteria-treated non-obese diabetic (NOD) mice, in order to assess its suitability as a model for studying the aetiopathogenesis of, and possible treatment options for, lupus nephritis (LN) in humans. Both global and segmental proliferative lesions, characterized by increased mesangial matrix and cellularity, were demonstrated on light microscopy, and lesions varied in severity from very mild mesangiopathic GN through to obliteration of capillary lumina and glomerular sclerosis. Mixed isotype immune complexes (IC) consisting of immunoglobulin G (IgG), IgM, IgA and complement C3c were detected using direct immunofluorescence. They were deposited in multiple sites within the glomeruli, as confirmed by electron microscopy. The GN seen in mycobacteria-treated NOD mice therefore strongly resembles the pathology seen in human LN, including mesangiopathic, mesangiocapillary and membranous subclasses of LN. The development of spontaneous mixed isotype IC in the glomeruli of some senescent NOD mice suggests that mycobacterial exposure is accelerating, rather than inducing, the development of GN in this model.

Genetic analysis of autoimmune sialadenitis in nonobese diabetic mice: a major susceptibility region on chromosome 1

The nonobese diabetic (NOD) mouse strain provides a good study model for Sjögren's syndrome (SS). The genetic control of SS was investigated in this model using different matings, including a (NOD x C57BL/6 (B6))F(2) cross, a (NOD x NZW)F(2) cross, and ((NOD x B6) x NOD) backcross. Multiple and different loci were detected depending on parent strain combination and sex. Despite significant complexity, two main features were prominent. First, the middle region of chromosome 1 (chr.1) was detected in all crosses. Its effect was most visible in the (NOD x B6)F(2) cross and dominated over that of other loci, including those mapping on chr.8, 9, 10, and 16; the effect of these minor loci was observed only in the absence of the NOD haplotype on chr.1. Most critically, the chr.1 region was sufficient to trigger an SS-like inflammatory infiltrate of salivary glands as shown by the study of a new C57BL/6 congenic strain carrying a restricted segment derived from NOD chr.1. Second, several chromosomal regions were previously associated with NOD autoimmune phenotypes, including Iddm (chr.1, 2, 3, 9, and 17, corresponding to Idd5, Idd13, Idd3, Idd2, and Idd1, respectively), accounting for the strong linkage previously reported between insulitis and sialitis, and autoantibody production (chr.10 and 16, corresponding to Bana2 and Bah2, respectively). Interestingly, only two loci were detected in the (NOD x NZW)F(2) cross, on chr.1 in females and on chr.7 in males, probably because of the latent autoimmune predisposition of the NZW strain. Altogether these findings reflect the complexity and heterogeneity of human SS.

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.

Bcg and autoimmunity: another two-edged sword

BCG immunotherapy for bladder carcinoma has been a long-standing treatment modality that has proved itself efficient and safe. Most of the side-effects of this treatment are minor and of short duration. There have been, nevertheless, several reports regarding more severe and long-term complications of BCG therapy-namely inflammatory arthritis, and occasionally systemic autoimmune manifestations. Here, we present four cases of patients who received intravesical instillation with BCG for bladder carcinoma and developed long-standing inflammatory arthritis. One of these patients developed Reiter's syndrome. We also refer to the possible immune mechanisms by which BCG can trigger arthritis, as well as to the link between mycobacterial infection, BCG immunotherapy and autoimmunity.