Direct evidence for the contribution of the unique I-ANOD to the development of insulitis in non-obese diabetic mice

Determinant capture as a possible mechanism of protection afforded by major histocompatibility complex class II molecules in autoimmune disease

How peptide-major histocompatibility complex (MHC) class II complexes are naturally generated is still unknown, but accumulating evidence suggests that unfolding proteins or long peptides can become bound to class II molecules at the dominant determinant before proteolytic cleavage. We have compared the immunogenicity of hen egg-white lysozyme (HEL) in nonobese diabetic (NOD), (NOD x BALB/c)F1, and E(d) alpha transgenic NOD mice. We find that a response to the subdominant ANOD-restricted determinant disappears upon introduction of an E(d) molecule, and is restored when scission of HEL separates this determinant from its adjoining, competitively dominant, E(d)-restricted determinant. This suggests that the E(d) molecule binds and protects its dominant determinant on a long peptide while captured neighboring determinants are lost during proteolysis. These results provide clear evidence for "determinant capture" as a mechanism of determinant selection during antigen processing and a possible explanation for MHC-protective effects in insulin-dependent diabetes mellitus.

An Abd transgene prevents diabetes in nonobese diabetic mice by inducing regulatory T cells

Susceptibility to the human autoimmune disease insulin-dependent diabetes mellitus is strongly associated with particular haplotypes of the major histocompatibility complex (MHC). Similarly, in a spontaneous animal model of this disease, the nonobese diabetic (NOD) mouse, the genes of the MHC play an important role in the development of diabetes. We have produced transgenic NOD mice that express the class II MHC molecule I-Ad in addition to the endogenous I-Ag7 molecules in order to study the role of these molecules in the disease process. Although the inflammatory lesions within the islets of Langerhans in the pancreas appear similar in transgenic and nontransgenic animals, transgenic mice develop diabetes with greatly diminished frequency compared to their nontransgenic littermates (10% of transgenic females by 30 weeks of age compared to 45% of nontransgenic females). Furthermore, adoptive transfer experiments show that T cells present in the transgenic mice are able to interfere with the diabetogenic process caused by T cells from nontransgenic mice. Thus, the mechanism by which I-Ad molecules protect mice from diabetes includes selecting in the thymus and/or inducing in the periphery T cells capable of inhibiting diabetes development.

The effect of bone marrow and thymus chimerism between non-obese diabetic (NOD) and NOD-E transgenic mice, on the expression and prevention of diabetes

The non-obese diabetic (NOD) mouse is an established animal model of the autoimmune disease, insulin-dependent diabetes mellitus (IDDM). The NOD-E mouse is a transgenic mouse which expresses the I-E molecule (absent in NOD mice). Expression of I-E protects these mice from both insulitis and IDDM. We have investigated the possible mechanisms of this protection by constructing bone marrow, and combined bone marrow and thymus chimeras between NOD and NOD-E mice. Our data suggest that thymic epithelium may play no direct role in either protection against, or promotion of, IDDM. Protection from diabetes is provided either by NOD-E donor bone marrow or NOD-E recipient non-thymic radioresistant cells. The means by which protection may be achieved in this system are discussed.

Prevention of systemic lupus erythematosus in autoimmune BXSB mice by a transgene encoding I-E alpha chain

Males from the BXSB murine strain (H-2b) spontaneously develop an autoimmune syndrome with features of systemic lupus erythematosus (SLE), which results in part from the action of a mutant gene (Yaa) located on the Y chromosome. Like other H-2b mice, the BXSB strain does not express the class II major histocompatibility complex antigen, I-E. Here we report that the expression of I-E (E alpha dE beta b) in BXSB males bearing an E alpha d transgene prevents hypergammaglobulinemia, autoantibody production, and subsequent autoimmune glomerulonephritis. These transgenic mice bear on the majority of their B cells not only I-E molecules, but also an I-E alpha chain-derived peptide presented by a higher number of I-Ab molecules, as recognized by the Y-Ae monoclonal antibody. The I-E+ B cells appear less activated in vivo than the I-E- B cells, a minor population. This limited activation of the I-E+ B cells does not reflect a functional deficiency of this cell population, since it can be stimulated to IgM production in vitro by lipopolysaccharides at an even higher level than the I-E- B cell population. The development of the autoimmune syndrome in the transgenic and nontransgenic bone marrow chimeric mice argues against the possibility that the induction of regulatory T cells or clonal deletion of potential autoreactive T cells as a result of I-E expression is a mechanism of the protection conferred by the E alpha d transgene. We propose a novel mechanism by which the E alpha d transgene protects BXSB mice against SLE: overexpression of I-E alpha chains results in the generation of excessive amounts of a peptide displaying a high affinity to the I-Ab molecule, thereby competing with pathogenic autoantigen-derived peptides for presentation by B lymphocytes and preventing their excessive stimulation.

I-E+ nonobese diabetic mice develop insulitis and diabetes

The development of type I diabetes in the nonobese diabetic (NOD) mouse is under the control of multiple genes, one or more of which is linked to the major histocompatibility complex (MHC). The MHC class II region has been implicated in disease development, with expression of an I-E transgene in NOD mice shown to provide protection from insulitis and diabetes. To examine the effect of expressing an I-E+ or I-E- non-NOD MHC on the NOD background, three I-E+ and three I-E- NOD MHC congenic strains (NOD.H-2i5, NOD.H-2k, and NOD.H-2h2, and NOD.H-2h4, NOD.H-2i7, and NOD.H-2b, respectively) were developed. Of these strains, both I-E+ NOD.H-2h2 and I-E- NOD.H-2h4 mice developed insulitis, but not diabetes. The remaining four congenic strains were free of insulitis and diabetes. These results indicate that in the absence of the NOD MHC, diabetes fails to develop. Each NOD MHC congenic strain was crossed with the NOD strain to produce I-E+ and I-E- F1 mice; these mice thus expressed one dose of the NOD MHC and one dose of a non-NOD MHC on the NOD background. While a single dose of a non-NOD MHC provided a large degree of disease protection to all of the F1 strains, a proportion of I-E+ and I-E- F1 mice aged 5-12 mo developed insulitis and cyclophosphamide-induced diabetes. When I-E+ F1 mice were aged 9-17 mo, spontaneous diabetes developed as well. These data are the first to demonstrate that I-E+ NOD mice develop diabetes, indicating that expression of I-E in NOD mice is not in itself sufficient to prevent insulitis or diabetes. In fact, I-E- F1 strains were no more protected from diabetes than I-E+ F1 strains, suggesting that other non-NOD MHC-linked genes are important in protection from disease. Finally, transfer of NOD bone marrow into irradiated I-E+ F1 recipients resulted in high incidences of diabetes, indicating that expression of non-NOD MHC products in the thymus, in the absence of expression in bone marrow-derived cells, is not sufficient to provide protection from diabetes.

RFLP analysis of the MHC class III region defines unique haplotypes for the non-obese diabetic, cataract Shionogi and the non-obese non-diabetic mouse strains

The non-obese diabetic (NOD) mouse strain which spontaneously develops diabetes is a model for human Type 1 (insulin-dependent) diabetes mellitus. At least one of several genes controlling diabetes in the NOD mouse has been mapped to the MHC. Although previous experiments have implicated the MHC class II genes in the development of the disease, the existence of other MHC linked susceptibility genes has not been ruled out. In order to identify these susceptibility genes we have further characterized the MHC haplotype of the NOD mouse and two non-diabetic sister strains, the non-obese non-diabetic (NON) and cataract Shionogi (CTS). We have examined the mouse MHC class III region for the presence of homologous genes to 17 newly isolated human MHC class III region genes (G1, G2, G4, G6, G7a/valyl-tRNA synthetase, HSP70, G8, G9, G10, G12, G13, G14, G15, G16, G17 and G18). We detect unique hybridizing DNA fragments for 16 of the 17 genes in six inbred mouse strains (NOD, NON, CTS, B10, BALB/c and CBA/J) indicating that this part of the H-2 region is similar to the human MHC class III region. Using a panel of restriction enzymes we have defined RFLPs for 6 (G2, G6, HSP70, G12, G16, G18) of the 16 cross-hybridizing probes. The RFLPs demonstrate that NOD, NON and CTS mouse strains each have a distinct MHC haplotype in the MHC class III region.

A comparative study on T cell receptor V beta gene usages: spleen cells from the non-obese diabetic (NOD) mouse and its non-diabetic sister strain, the ILI mouse, and infiltrating T cells into pancreata of NOD mice

We analyzed the usage of T cell receptor (TCR) V beta genes of spleen cells of NOD mice in comparison with those of its non-diabetic sister strain ILI mice which show no insulitis and (ILI x NOD)F1 mice. The quantitative polymerase chain reaction (PCR) method revealed that PCR V beta repertoires of these mice are indistinguishable. This is consistent with our previous observation that ILI mice share the same H-2 class II genes with NOD mice. PCR method also revealed that the V beta transcript of infiltrating T cells into pancreas of NOD mice was not restricted but was rather diverse. The role of TCR repertoire in the development of insulitis was discussed.

Pancreatic beta-cell destruction in non-obese diabetic mice

We determined the natural history of the widespread pancreatic islet beta-cell destruction that precedes the onset of spontaneous putative autoimmune diabetes mellitus in NOD mice. For this purpose, we performed both histological and immunocytochemical examinations of pancreata retrieved from mice at 2 through 30 weeks of age. An overexpression of la antigens was identified on islet beta cells at 4 weeks of age, without evidence of mononuclear cell infiltration. The abnormal expression of la antigens was age-related and was associated with hyperexpression of class I antigens and progressive islet cell histologic damage after 17 weeks of age. Immunocytochemical examination of islet cell infiltrate showed that the number of macrophages did not increase during the early phase of islet cell damage in these mice. The L3T4/Lyt-2 ratio increased after 7 weeks of age, but was 1:1 in the late stage of insulitis. These findings suggest that widespread islet beta-cell destruction is a process that begins primarily with derangements of the pancreatic beta-cell immune pattern, which may trigger a mononuclear cell reaction.

Three-dimensional structure of the human class II histocompatibility antigen HLA-DR1

The three-dimensional structure of the class II histocompatibility glycoprotein HLA-DR1 from human B-cell membranes has been determined by X-ray crystallography and is similar to that of class I HLA. Peptides are bound in an extended conformation that projects from both ends of an 'open-ended' antigen-binding groove. A prominent non-polar pocket into which an 'anchoring' peptide side chain fits is near one end of the binding groove. A dimer of the class II alpha beta heterodimers is seen in the crystal forms of HLA-DR1, suggesting class II HLA dimerization as a mechanism for initiating the cytoplasmic signalling events in T-cell activation.

Self-nonself discrimination and tolerance in T and B lymphocytes

The immune system must not only fight off infections, but also ensure that it does not react against its own body tissues. Since clones of lymphocytes have predetermined reactivities, some will be self-reactive and have the potential to cause damage. They should therefore be neutralized in some way. In a system as complex and important as that governing self-tolerance, many mechanisms must exist to neutralize autoaggressive lymphocytes. They may be classified under two main groups. In one the tolerant state arises from the physical or functional silencing of potentially autoaggressive lymphocytes after antigen encounter. This may involve clonal deletion, clonal abortion or clonal anergy. In the second, regulatory mechanisms of the immune system itself may hold autoreactive lymphocytes in check, for example through the operation of idiotypic network interactions and the action of specialized suppressor cells. Much evidence has accumulated for the physical deletion of autoreactive T cells as they mature in the thymus. The fate of any that escape thymus censorship has been the subject of recent research and is discussed here. Under certain conditions, self-tolerance must also be imposed at the B-cell level to prevent the production of potentially damaging autoantibodies. Although the mechanisms which silence self-reactive lymphocytes are very efficient, self-tolerance can break down, and autoimmunity will thus ensue. The main factors responsible for this are briefly described here.

Type 1 diabetes mellitus: an imbalance between effector and regulatory T cells?

Abundant evidence now exists that autoimmunity plays a critical role in the pathogenesis of type 1 (insulin-dependent) diabetes mellitus. The non-obese diabetic (NOD) mouse is an extensively studied animal model of this T-cell-mediated autoimmune disease. Our laboratory has focused on isolating diabetogenic T cell clones from NOD mice as a means of elucidating the pathogenesis of type 1 diabetes. This experimental approach presupposes that type 1 diabetes in NOD mice results from the action of islet-reactive T cells that are not present in other mouse strains; the diabetogenic T cells would therefore represent "forbidden clones" which exist in NOD mice as a result of a failure of clonal deletion. While the inappropriate presence of diabetogenic T cells probably plays a central role in murine diabetes, it cannot explain all aspects of the disease. Type 1 diabetes is a chronic disorder with a lengthy preclinical stage; if the diabetogenic T cells acted in an unopposed fashion, one might expect to see a much more fulminant clinical course. This observation suggests that regulatory influences are likely to exist in this disease--a possibility supported by recent experimental data. If these regulatory influences could be identified and enhanced, specific immunotherapy for type 1 diabetes could be achieved.

Intervention therapies for insulin-dependent diabetes

Treatment of insulin-dependent diabetes remains problematic since there continues to be high rates of morbidity and mortality among affected patients. Good outcomes are most likely to be more common among patients who maintain endogenous insulin reserves for the longest time following diagnosis. The disease process can now be identified in its early, pre-symptomatic stages and thus, the time has come for the investigation of preventive therapies through multicenter clinical trials. A wide variety of strategies are available and their choice should be dependent on the pathogenic stage of disease at which treatment is initiated. This stage-specific approach to prevention is discussed with a particular focus on those therapies that will soon be tested in clinical trials.

Transgenes in autoimmunity

The ability of transgenic mice to express a specific protein in a specific tissue has enabled the mechanisms of self-tolerance and autoimmunity to be elucidated. Further studies, combined with more sophisticated methods of gene targeting, will provide insights into the pathway leading from loss of self-tolerance to autoimmunity.

Prevention of autoimmune insulitis in nonobese diabetic mice by expression of major histocompatibility complex class I Ld molecules

Nonobese diabetic (NOD) mice spontaneously develop a T-cell-mediated autoimmune disease that is similar in many respects to insulin-dependent diabetes mellitus in humans. NOD mice were shown to express major histocompatibility complex class I Kd and Db antigens. To examine the possible involvement of major histocompatibility complex class I molecules in the development of autoimmune insulitis, we attempted to express a different type of class I molecule in NOD mice by crossing C57BL/6 mice transgenic for the class I Ld gene with NOD mice. The backcross progeny expressed the Ld antigen on the peripheral blood lymphocytes at a level comparable with that of the BALB/c mice. The cell surface expression of endogenous class I and class II antigens on the peripheral blood lymphocytes was not affected. Analysis of these mice revealed that the expression of the class I Ld antigen significantly reduced the incidence of insulitis at 20 weeks of age. In situ hybridization of a biotinylated probe on mouse chromosomes showed that the Ld transgene was located in the E area of chromosome 6 with which no genetic linkage to insulin-dependent diabetes mellitus was demonstrated. These results suggest that the NOD-type class I molecules are involved in the development of insulitis in NOD mice.

Acquired allo-tolerance to major or minor histocompatibility antigens indifferently contributes to preventing diabetes development in non-obese diabetic (NOD) mice

Diabetes in NOD mice represents the end stage of a genetically-programmed autoimmune process mediated by T lymphocytes and directed against insulin-producing beta cells. We have shown in a previous study that the course of the disease is significantly inhibited in NOD mice which have been made tolerant at birth to foreign histocompatibility antigens. This early T cell manipulation results in a significant delay of disease onset, reduced overall incidence and less severe alterations of islet cells. In order to characterize better the nature of the foreign tolerogenic determinants responsible for this protection, we have now examined separately the contribution of MHC and non-MHC antigens. Two lines of congenic mice were used as donors of tolerogenic cells, NOD.H-2b, which differ from NOD by the MHC-encoded antigens only, and B10.H-2g7, which differ by all the minor histocompatibility antigens encoded by the B10 background, but which share with NOD mice the same MHC haplotype. Our results show that NOD recipients of F1 semi-compatible cells become specifically tolerant to the set of alloantigens to which they were neonatally exposed. Unresponsiveness, assessed by lack of CTL generation, is profound and specific. Yet, despite the fact that distinct sets of alloreactive T cell precursors are silenced, mice made tolerant indifferently to major or minor histocompatibility antigens are significantly protected against overt diabetes. These results could mean that each set of MHC and non-MHC encoded determinants can independently cross-tolerize a sufficient proportion of the autoreactive repertoire to slow the natural course of the disease. Alternatively, neonatally-acquired tolerance might induce polyclonal activation of the immune system resulting in the suppression or the immunodeviation of potentially harmful, autoreactive T cell clones.

The HLA DQB1*0502 allele is neutrally associated with insulin-dependent diabetes mellitus in the Sardinian population

In the Sardinian population a very high incidence of insulin-dependent diabetes mellitus (IDDM) and the lack of HLA-DR2 protective effect due to the high frequency of the A2, Cw7, B17, 3F31, DR2, DQw1 extended haplotype has been reported. This haplotype, carrying a Serine at position 57 of the DQB1*0502 allele, has been previously reported to be underrepresented in patients when compared to controls. In order to provide an explanation for this finding, we defined by RFLP analysis the HLA haplotype of 45 Sardinian IDDM patients and 49 controls. All DR-2DQw1 subjects were molecularly characterized at the HLA DQA and DQB loci. All DR2-positive patients and the vast majority of the DR2-positive controls had the DQB1*0502 allele at the DR2-linked DQB1 locus, with no statistically significant difference between the two groups. All DQA1 genes were the ones expected, with only two exceptions. Nine out of 10 of the DR2-positive patients were compound heterozygotes for DQB1*0201/DQB1*0502 alleles; only this allele combination was significantly increased (p less than 0.0003). Our data suggests that a) the DQB1*0502 allele is neutral for IDDM development and b) the susceptibility to IDDM in our DR2-positive patients is related to the compound heterozygous state between the neutral DQA1*0102/DQB1*0502 and the susceptibility DQA1*0501/DQB1*0201 alleles.

Transgenic mouse as a tool for the study of autoimmune disease: insulin-dependent diabetes mellitus

Transgenic mice have been used for analyses of cis-acting elements which are involved in the tissue-specific and developmental-specific expression, for analyses of physiological function of genes, or for the production of a human disease model. This approach is especially successful in the fields of immunology and oncology. Several years ago it was shown that the major histocompatibility complex (MHC) class II gene is identical to the immune response gene by demonstrating that the immune response can be restored by the new expression of class II molecules on immunocompetent cells. Recent evidence suggests that the class II molecule is involved in the generation of autoimmune disease, such as insulin-dependent diabetes mellitus (IDDM). The NOD (non-obese diabetic) mouse is shown to be a mouse model for human IDDM. Concerning the class II genes, the NOD mouse has two characteristic features, the lack of I-E and the presence of unique I-A. It is discussed how the role of class II molecules in the development of IDDM in the NOD mouse can be analyzed. In addition, the transgenic technique can be applied to the study of differentiation and oncogenesis of lymphoid cells. Factors or molecules that affect these processes will also be discussed.

Altered course of visceral leishmaniasis in mice expressing transgenic I-E molecules

Previous studies had shown that the outcome of infection with Leishmania donovani was exquisitely sensitive to the influence of the major histocompatibility complex. In this study, we have examined the course of infection in non-obese diabetic (NOD) and NOD-E-3 mice, the latter expressing an I-E molecule as a result of transgenic introduction of the wild-type Ed alpha gene. Introduction of this transgene significantly altered the course of infection allowing for enhanced parasite multiplication in the viscera from day 14 to day 28. This was associated with both a delayed and reduced tissue granulomatous response in NOD-E-3 mice. In vitro, spleen cells from these mice produced equivalent levels of interferon (IFN)-gamma during the early phase of infection but this originated from populations having a different balance of T cells subsets. In NOD mice CD8+ T cells contribute substantially to the total levels of IFN-gamma produced, but in transgenic mice the contribution from this subset is significantly decreased. This is reflected in a reduction in the proportion of Leishmania-specific CD8+ T cells, which could only partially be accounted for by deletion of V beta 5- and V beta 3-expressing CD8+ T cells in NOD-E-3 mice. This study highlights the impact of the introduction of a class II gene product on disease outcome and unexpectedly on the functional potential of CD8+ T cells.

Analysis of the T cell receptor (TcR) regions in the NOD, NON and CTS mouse strains define new TcR V alpha haplotypes and new deletions in the TcR V beta region

We have analyzed the T cell receptor (TcR) V alpha and TcR V beta regions in the spontaneous mouse model for insulin-dependent diabetes mellitus, the NOD mouse, and compared it to the regions in the two sister strains, the NON and CTS strains. Based on restriction fragment length polymorphism analysis the TcR V alpha region in the NOD mouse is essentially identical to that of the SJL/J strain. In contrast both the NON and CTS strains have a unique TcR V alpha haplotype. Whereas the NOD and NON strains apparently contains all the TcR V beta genes, the CTS mouse has three deletions in the V beta region. Our analysis does not give any indications for the diabetic phenotype of the NOD mouse.

Complete prevention of diabetes in transgenic NOD mice expressing I-E molecules

Previously, we showed that transgenic expression of the MHC (major histocompatibility complex) class II I-E molecules prevented insulitis in non-obese diabetic (NOD) mice at the age of 19 weeks. To rule out the possibility that the I-E expression merely delays the onset of insulitis, we have further characterized the expression and function of the I-E molecule expressed in transgenic NOD mice and confirmed our previous observations. Northern blot analysis showed that the transgenic E alpha d gene was expressed in a pattern similar to the endogenous E alpha d gene in BALB/c mice. The newly expressed I-E molecules were recognized as an alloantigen by the T lymphocytes of normal NOD mice as shown by mixed lymphocyte reaction (MLR). Transgenic NOD mice were resistant to the treatment by cyclophosphamide, which effectively induces diabetes in normal NOD mice, and did not develop diabetes up to 40 weeks of age. On the basis of these findings, we discuss the role of I-E molecules in the prevention of diabetes in NOD mice.

Linkage of faulty major histocompatibility complex class I to autoimmune diabetes

Pancreatic islet cells are the targets of an autoimmune response in type I diabetes. In the nonobese diabetic (NOD) mouse model of autoimmune diabetes, expression of major histocompatibility complex (MHC) class I proteins was inversely correlated with diabetes; in this mouse a mutation in the MHC class II-linked gene for the putative MHC class I peptide transporter was also present. Mice deficient in MHC class I expression because they do not produce beta 2-microglobulin also developed late onset autoimmune diabetes. In cells from humans with type I diabetes expression of MHC class I was decreased; subsets of prediabetics categorized as most likely to become hyperglycemic also had low MHC class I. T cell responses to self antigens are faulty in diabetics. In sets of genetically identical twins that are discordant for diabetes, the defect appeared to reside with the antigen presenting cell. Thus, a lack of surface MHC class I protein is associated with autoimmune diabetes; the concomitant defect in antigen presentation may impair the development of self tolerance, which could result in autoimmune disease.

Regulation of autoimmunity

Despite the prevalence of self-reactive T cells, the healthy organism is not in a state of all-out war. Potent regulatory mechanisms exist at every level to permit the successful integration of the various aspects of the immune system, allowing only minor skirmishes, which ordinarily can be neutralized.

Insulin-dependent diabetes mellitus

Type I diabetes occurs as a result of T-cell-mediated beta-cell destruction. Several candidate antigens have been described recently, including glutamic acid decarboxylase, heat shock protein 65 and peripherin. Restricted T-cell receptor V beta gene usage in non-obese diabetic mice has been suggested but not yet proven. In addition to major histocompatibility genes, several non-H-2 predisposing genes have been mapped on chromosomes 1, 3 and 11.

The phenotype of lymphoid cells and thymic epithelium correlates with development of autoimmune insulitis in NOD in equilibrium with C57BL/6 allophenic chimeras

The mechanisms contributing to the development of autoimmune insulin-dependent diabetes mellitus have been analyzed in allophenic mouse chimeras of the NOD in equilibrium with C57BL/6 strain combination (where NOD is nonobese diabetic). Occurrence of lymphoid cell infiltration (insulitis) in pancreatic islets was observed in the majority of such chimeras. The development of insulitis was found to correlate with major histocompatibility complex chimerism in lymphoid cells and in thymus cortical regions. Chimeras with more than 50% of C57BL/6 lymphoid cells rarely developed insulitis. Our data suggest that the correlation with the thymic cortical region is absolute. Thus, all individuals displaying NOD or NOD/C57BL/6 thymic cortical regions developed insulitis, whereas we have not observed insulitis in chimeras with only C57BL/6 thymic cortical regions. Thus the positive selection of T cells appears to play a crucial role in the development of insulin-dependent diabetes mellitus.

Monoclonal, natural antibodies prevent development of diabetes in the non-obese diabetic (NOD) mouse

The development of diabetes in the non-obese diabetic (NOD) mouse is mediated by T cells of both the CD4+CD8- and CD4-CD8+ phenotypes, while B cells are not involved in the effector stage of the disease. We have recently found, however, that treatments with heterologous, polyclonal immunoglobulin (Ig) preparations, as well as suppressing the developing B cell repertoire for the first 4 weeks of life dramatically reduce the incidence of disease and the severity of insulitis, in treated mice. We have further investigated the influence of Igs on the development of autoimmunity by testing the effect of polyclonal mouse-Ig or monoclonal, natural antibodies derived from normal, neonatal BALB/c mice. We found that repeated administration of high doses of polyclonal Ig (of xenogenic or isogenic origin), given at birth, inhibits the development of insulitis, as well as diabetes. Furthermore, single injections of moderate doses of isogenic, natural monoclonal antibodies (mAb) administered at the same age, while failing to significantly alter the degree of insulitis, efficiently prevent the development of disease. The effect of mAbs was found to be related to V-region specificity, as only some mAbs of a given isotype and origin had the observed effect.

The role of genetic predisposition to type I (insulin-dependent) diabetes mellitus

The aetiology of insulin-dependent diabetes (IDDM) involves genetic predisposition, a major component of which has been mapped in the HLA complex, near to or identical with genes encoding class II molecules. In Caucasian populations IDDM is strongly associated with the serologically defined HLA-DR3 and DR4 antigens, which are widely recognised as markers of susceptibility. The particularly high risk of DR3/DR4 heterozygotes suggests that susceptibility is determined by two genes acting synergistically. The development of recombinant DNA technology has allowed a finer description of the class II region and provided evidence that DQ rather than DR determinants may primarily influence IDDM susceptibility. The search for specific structural changes of the DQA and DQB genes has shown that susceptibility correlates with the absence of aspartic acid at position 57 on the DQ beta chain (DQ beta 57 Asp--) and/or the presence of arginine at position 52 on the DQ alpha chain (DQ alpha 52 Arg+). In Caucasians the formation of a putative DQ susceptibility molecule (DQ alpha 52 Arg+, DQ beta 57 Asp-) accounts best for the disease associations when transcomplementation molecules consisting of DQ alpha and beta chains encoded by different haplotypes are postulated to explain the excess risk of heterozygotes. The HLA-IDDM associations in the Japanese, however, are not explained by this model. These and other unresolved questions indicate that other residues of the DQ alpha and beta chains or other class II molecules (DR beta chains), as well as non-MHC genes, may also contribute to the susceptibility.

Type 1 diabetes in mice is linked to the interleukin-1 receptor and Lsh/Ity/Bcg genes on chromosome 1

Human type 1 (insulin-dependent) diabetes is a common auto-immune disease of the insulin-producing beta cells of the pancreas which is caused by both genetic and environmental factors. Several features of the genetics and immunopathology of diabetes in nonobese diabetic (NOD) mice are shared with the human disease. Of the three diabetes-susceptibility genes, Idd-1 -3 and -4 that have been mapped in mice to date, only in the case of Idd-1 is there any evidence for the identity of the gene product: allelic variation within the murine immune response I-A beta gene and its human homologue HLA-DQB1 correlates with susceptibility, implying that I-A beta is a component of Idd-1. We report here the mapping of Idd-5 to the proximal region of mouse chromosome 1. This region contains at least two candidate susceptibility genes, the interleukin-1 receptor gene and Lsh/Ity/Bcg, which encodes resistance to bacterial and parasitic infections and affects the function of macrophages.

Transgenic regulation in laboratory animals

This chapter is an attempt to summarize some commonly accepted and some more subjective opinions about the regulation of transgene expression in laboratory animals. After a short historical introduction, I present some general notions regarding gene structure/function. The spotlight shifts then to the description of the most popular techniques for gene transfer, including the targeted gene replacement. The different approaches are briefly discussed in terms of intrinsic advantages and limitations regarding gene expression patterns. Furthermore, the role of enhancers, promoters and other cis-acting elements such as silencers and dominant control regions as well as their involvement in the chromatin on-off state are discussed on the basis of a specific example studied in our laboratory. The review concludes by presenting recent results and the new perspectives opening in the field of 'surrogate' (also called 'reversed') genetics. Some problems which remain to be solved both at the technical as well as at the social-ethical level are also briefly presented.

HLA class II sequences and genetic susceptibility to insulin dependent diabetes mellitus

The analysis of HLA class II sequence variation in IDDM patients and controls, made possible by the PCR, has revealed that specific alleles are associated with IDDM. The HLA-DQ beta chain appears to play a role in determining genetic susceptibility and resistance, although polymorphisms in the DRB1, the DQ alpha, and the DP beta chain may also contribute. Although there is a correlation between susceptibility and the charge of DQ beta residue 57, the complex genetic epidemiology of IDDM cannot be accounted for by polymorphism at this position. As we have discussed previously (Horn et al, 1988a, 1988b; Erlich et al, 1990b), there are no unique class II sequences associated with IDDM, consistent with the view that 'normal' class II alleles confer susceptibility. Given the estimates of concordance of under 50% for monozygotic twins and approximately 15% (Tattersall and Pyke, 1972; Thomson, 1988) for HLA-identical sibs--it is not surprising that some unaffected individuals contain putative susceptibility alleles. Perhaps some environmental 'triggering' agent, such as viral infection, is required for the disease to develop in susceptible individuals. Other non-MHC-linked genes which contribute to susceptibility may account for the difference in concordance rates for monozygotic twins and for HLA-identical sibs. In the NOD (non-obese diabetic) mouse and the BB rat models for IDDM, non-MHC susceptibility loci have been identified and mapped (Colle et al, 1981; Hattori et al, 1986) but, in humans, the analysis of non-MHC candidate loci (i.e. the T cell receptor) has, thus far, failed to reveal any other susceptibility loci. In general, the HLA-linked genetic susceptibility to IDDM, as well as to other autoimmune diseases, appears to be associated with specific combinations of class II epitopes (e.g. alleles, haplotypes or genotypes) rather than with specific individual residues or epitopes. Understanding the role of these predisposing sequences will require structural analysis of the class II molecules as well as in vitro and in vivo functional studies of interactions with putative autoantigens and T cell receptors. In the meantime, DNA typing offers the potential for identifying individuals at high risk. These susceptible individuals could be monitored by immunological (e.g. anti-islet cell antibody) or by metabolic tests to detect the preclinical phase of IDDM.

Genetic analysis of autoimmune type 1 diabetes mellitus in mice

Two genes, Idd-3 and Idd-4, that influence the onset of autoimmune type 1 diabetes in the nonobese diabetic mouse have been located on chromosomes 3 and 11, outside the chromosome 17 major histocompatibility complex. A genetic map of the mouse genome, analysed using the polymerase chain reaction, has been assembled specifically for the study. On the basis of comparative maps of the mouse and human genomes, the homologue of Idd-3 may reside on human chromosomes 1 or 4 and Idd-4 on chromosome 17.

Transgenic mice for the study of diabetes mellitus

Several recent studies have utilized transgenic technology to explore basic questions in the pathophysiology of diabetes mellitus. The ultimate expression of altered glucose homeostasis is a theme common to them. The experimental models have been diverse, however, and, in some instances, resulted in unexpected biologic effects. Many of the studies have examined the autoimmune etiology of insulin-dependent diabetes mellitus by expressing regulatory molecules of the immune system as transgenes in islet beta cells. The molecules have included products of the major histocompatibility complex (MHC), cytokines, and other cell surface antigens. Ectopic expression of these transgenes resulted in altered immune responses directed against islets, and these transgenic mice now serve as important models to study mechanisms of immunologic tolerance. Transgenic technology is also being used to explore basic aspects of islet beta-cell physiology and insulin metabolism. beta-cell function is disrupted by transgenic beta-cell expression of molecules such as calmodulin and H-ras. Hyperexpression of insulin as a transgene can result in a syndrome resembling features of non-insulin-dependent diabetes.

Islet-infiltrating T cell clones from non-obese diabetic mice that promote or prevent accelerated onset diabetes

In humans and non-obese diabetic mice (NOD), insulin-dependent diabetes mellitus (IDDM) results from a spontaneous T cell-dependent autoimmune destruction of the insulin-producing pancreatic beta cells. Previous data suggest that a delicate balance between autoaggressive T cells and suppressor-type immune phenomena determine whether expression of autoimmunity is limited to insulitis or progresses to IDDM. To resolve the cellular basis of this intricate network of pathogenic CD4+ and CD8+ T cells and the role of T cells in suppressive immune phenomena. T cell clones were propagated directly from islets of NOD mice at the onset of insulitis. Insofar as insulitis, but not IDDM, is universal in NOD mice, we have screened for the in vivo effects of the islet-infiltrating T cell clones upon expression of IDDM, not insulitis. A CD4+ T cell clone, IS-3S7D, proliferates in response to islet antigen(s) and its transfer into prediabetic NOD mice promotes the rapid onset of IDDM. An interleukin 2 (IL 2)-dependent noncytolytic, V beta 11+ CD8+. T cell clones IS-2.15, prevents an accelerated onset diabetes in two distinct models. The present study, which documents the presence of CD4+ diabetogenic T cell clones and CD8+ T cell clones that dampen autoimmunity, gives tangible evidence that opposing autoimmune processes may determine whether an autoimmune-prone host develops frank disease.

Transgenic mice as immune system models

In the past year, transgenic mice have continued to be powerful models for the investigation of various features of the immune system, particularly for studies of lymphocyte differentiation and tolerance. Major achievements have included the definition of intra-thymic selection events in T-cell differentiation, and the demonstration of extra-thymic tolerance resulting from clonal energy.

HLA-DQA1*1 contributes to resistance and A1*3 confers susceptibility to type 1 (insulin-dependent) diabetes mellitus in Japanese subjects

In this study HLA-DQA1 and TNF genes in addition to HLA-DQB1 gene were investigated at DNA level for elucidation of the genetic backgrounds of Type 1 (insulin-dependent) diabetes mellitus in Japanese subjects. DNA, amplified by polymerase chain reaction, was subjected to allele specific oligonucleotide dot blot analysis, restriction fragment length polymorphism analysis or DNA sequencing. Polymorphism of the TNF gene to NcoI did not correlate with Type 1 diabetes in Japanese patients. DQw1.2 had a protective effect against the disease, the DQA1*1 allele was significantly decreased and DQA1*3 allele was significantly increased. Seventeen out of twenty-two Type 1 diabetic patients (77%) were homozygous for DQA1*3 and five out of twenty-two (23%) heterozygous. The DQA1*3 gene of Type 1 diabetic patients had a normal nucleotide sequence. Furthermore, DQA1*3 was found unexpectedly in two patients without DR4 or DR9. These data indicate that DQA1 gene confers susceptibility and resistance to Type 1 diabetes in Japanese subjects.