Anchored polymerase chain reaction based analysis of the V beta repertoire in the non-obese diabetic (NOD) mouse

Endogenous retrovirus Gag antigen and its gene variants are unique autoantigens expressed in the pancreatic islets of non-obese diabetic mice

Endogenous retrovirus (ERV) are remnants of ancient retroviruses that have been incorporated into the genome and evidence suggests that they may play a role in the etiology of T1D. We previously identified a murine leukemia retrovirus-like ERV whose Env and Gag antigens are involved in autoimmune responses in non-obese diabetic (NOD) mice. In this study, we show that the Gag antigen is present in the islet stromal cells. Although Gag gene transcripts were present, Gag protein was not detected in diabetes-resistant mice. Cloning and sequencing analysis of individual Gag genes revealed that NOD islets express Gag gene variants with complete open-reading frames (ORFs), in contrast to the diabetes-resistant mice, whose islet Gag gene transcripts are mostly non-ORFs. Importantly, the ORFs obtained from the NOD islets are extremely heterogenous, coding for various mutants that are absence in the genome. We further show that Gag antigens are stimulatory for autoreactive T cells and identified one islet-expressing Gag variant that contains an altered peptide ligand capable of inducing IFN-gamma release by the T cells. The data highlight a unique retrovirus-like factor in the islets of the NOD mouse strain, which may participate in key events triggering autoimmunity and T1D.

Prenatal Administration of Betamethasone Causes Changes in the T Cell Receptor Repertoire Influencing Development of Autoimmunity

Prenatal glucocorticoids are routinely administered to pregnant women at risk of preterm delivery in order to improve survival of the newborn. However, in half of the cases, birth occurs outside the beneficial period for lung development. Glucocorticoids are potent immune modulators and cause apoptotic death of immature T cells, and we have previously shown that prenatal betamethasone treatment at doses eliciting lung maturation induce profound thymocyte apoptosis in the offspring. Here, we asked if there are long-term consequences on the offspring’s immunity after this treatment. In the non-obese diabetic mouse model, prenatal betamethasone clearly decreased the frequency of pathogenic T cells and the incidence of type 1 diabetes (T1D). In contrast, in the lupus-prone MRL/lpr strain, prenatal glucocorticoids induced changes in the T cell repertoire that resulted in more autoreactive cells. Even though glucocorticoids transiently enhanced regulatory T cell (Treg) development, these cells did not have a protective effect in a model for multiple sclerosis which relies on a limited repertoire of pathogenic T cells for disease induction that were not affected by prenatal betamethasone. We conclude that prenatal steroid treatment, by inducing changes in the T cell receptor repertoire, has unforeseeable consequences on development of autoimmune disease. Our data should encourage further research to fully understand the consequences of this widely used treatment.

Autoimmune Responses to Exosomes and Candidate Antigens Contribute to Type 1 Diabetes in Non-Obese Diabetic Mice

PURPOSE OF REVIEW

The initial autoimmune trigger of type 1 diabetes (T1D) remains unclear. In non-obese diabetic (NOD) mice, islet inflammation starts early in life, suggesting the presence of an endogenous trigger for the spontaneous autoimmune response in this T1D mouse model. In this review, we argue that abnormal release of exosomes might be the trigger of the early inflammatory and autoimmune responses in the islets.

RECENT FINDINGS

Exosomes are nano-sized membrane complexes that are secreted by cells following fusion of late endosomes and/or multivesicular bodies with the plasma membrane. They are known extracellular messengers, communicating among neighboring cells via transporting large molecules from parent cells to recipient cells. Recent evidence demonstrates that these extracellular vesicles can modulate immune responses. It has been shown that insulinoma and islet mesenchymal stem cell-released exosomes are potent immune stimuli that can induce autoreactive B and T cells. Searching for candidate antigens in the exosomes identified endogenous retrovirus (ERV) Env and Gag antigens, which are homologous to an endogenous murine leukemia retrovirus. Autoantibodies and autoreactive T cells spontaneously developed in NOD mice can react to these retroviral antigens. More importantly, expression of the retroviral antigens in the islet mesenchymal stem cells is associated with disease susceptibility, and the expression is restricted to T1D-susceptible but not resistant mouse strains. Exosomes are novel autoimmune targets, carrying autoantigens that can stimulate innate and adaptive immune responses. An abnormal or excess release of exosomes, particularly those ones containing endogenous retroviral antigens might be responsible for triggering tissue-specific inflammatory and autoimmune responses.

Autoreactive effector/memory CD4+ and CD8+ T cells infiltrating grafted and endogenous islets in diabetic NOD mice exhibit similar T cell receptor usage

Islet transplantation provides a “cure” for type 1 diabetes but is limited in part by recurrent autoimmunity mediated by β cell-specific CD4⁺ and CD8⁺ T cells. Insight into the T cell receptor (TCR) repertoire of effector T cells driving recurrent autoimmunity would aid the development of immunotherapies to prevent islet graft rejection. Accordingly, we used a multi-parameter flow cytometry strategy to assess the TCR variable β (Vβ) chain repertoires of T cell subsets involved in autoimmune-mediated rejection of islet grafts in diabetic NOD mouse recipients. Naïve CD4⁺ and CD8⁺ T cells exhibited a diverse TCR repertoire, which was similar in all tissues examined in NOD recipients including the pancreas and islet grafts. On the other hand, the effector/memory CD8⁺ T cell repertoire in the islet graft was dominated by one to four TCR Vβ chains, and specific TCR Vβ chain usage varied from recipient to recipient. Similarly, islet graft- infiltrating effector/memory CD4⁺ T cells expressed a limited number of prevalent TCR Vβ chains, although generally TCR repertoire diversity was increased compared to effector/memory CD8⁺ T cells. Strikingly, the majority of NOD recipients showed an increase in TCR Vβ12-bearing effector/memory CD4⁺ T cells in the islet graft, most of which were proliferating, indicating clonal expansion. Importantly, TCR Vβ usage by effector/memory CD4⁺ and CD8⁺ T cells infiltrating the islet graft exhibited greater similarity to the repertoire found in the pancreas as opposed to the draining renal lymph node, pancreatic lymph node, or spleen. Together these results demonstrate that effector/memory CD4⁺ and CD8⁺ T cells mediating autoimmune rejection of islet grafts are characterized by restricted TCR Vβ chain usage, and are similar to T cells that drive destruction of the endogenous islets.

T cell populations in the pancreatic lymph node naturally and consistently expand and contract in NOD mice as disease progresses

Nonobese diabetic (NOD) mice develop spontaneous autoimmune Type 1 diabetes (T1D) that results from the destruction of insulin secreting β cells by diabetogenic T cells. The activation of autoreactive T cells occurs in the pancreatic lymph nodes (PLN) from where effector T cells migrate to the pancreas. This study was designed to explore whether T cell populations in the NOD PLN expand in a predictable and reproducible way during disease progression. Complementary determining region (CDR) 3 length spectratype analysis of 19 TCR Vβ families was used to identify the relative frequency of T populations in PLN of 4 and 10 week old NOD mice and mice at T1D onset. Significant and highly reproducible changes in specific T cell populations were detected in 14 of Vβ families tested at all stages of disease. However, of these, the CDR3 spectratype of only four Vβ families was significantly more perturbed at T1D onset than in 10 week old mice. Intriguingly, when diabetes was induced in 10 week old mice with cyclophosphamide (CYP) the same four Vβ families, Vβ5.1, Vβ9, Vβ10, and Vβ15, were again significantly more perturbed than in the untreated non-diabetic age matched mice. Taken together the data show that while T cell responses in PLN of NOD mice are heterogeneous, they are ordered and consistent throughout disease development. The finding that within this heterogeneous response four Vβ families are significantly more perturbed in diabetic mice, whether spontaneous or induced, strongly suggests their selection as part of the disease process.

Spectratyping analysis of the islet-reactive T cell repertoire in diabetic NOD Igμ(null) mice after polyclonal B cell reconstitution

BACKGROUND

Non Obese Diabetic mice lacking B cells (NOD.Igμ(null) mice) do not develop diabetes despite their susceptible background. Upon reconstitution of B cells using a chimera approach, animals start developing diabetes at 20 weeks of age.

METHODS

We have used the spectratyping technique to follow the T cell receptor (TCR) V beta repertoire of NOD.Igμ(null) mice following B cell reconstitution. This technique provides an unbiased approach to understand the kinetics of TCR expansion. We have also analyzed the TCR repertoire of reconstituted animals receiving cyclophosphamide treatment and following tissue transplants to identify common aggressive clonotypes.

RESULTS

We found that B cell reconstitution of NOD.Igμ(null) mice induces a polyclonal TCR repertoire in the pancreas 10 weeks later, gradually diversifying to encompass most BV families. Interestingly, these clonotypic BV expansions are mainly confined to the pancreas and are absent from pancreatic lymph nodes or spleens. Cyclophosphamide-induced diabetes at 10 weeks post-B cell reconstitution reorganized the predominant TCR repertoires by removing potential regulatory clonotypes (BV1, BV8 and BV11) and increasing the frequency of others (BV4, BV5S2, BV9, BV16-20). These same clonotypes are more frequently present in neonatal pancreatic transplants under the kidney capsule of B-cell reconstituted diabetic NOD.Igμ(null) mice, suggesting their higher invasiveness. Phenotypic analysis of the pancreas-infiltrating lymphocytes during diabetes onset in B cell reconstituted animals show a predominance of CD19+ B cells with a B:T lymphocyte ratio of 4:1. In contrast, in other lymphoid organs (pancreatic lymph nodes and spleens) analyzed by FACS, the B:T ratio was 1:1. Lymphocytes infiltrating the pancreas secrete large amounts of IL-6 and are of Th1 phenotype after CD3-CD28 stimulation in vitro.

CONCLUSIONS

Diabetes in NOD.Igμ(null) mice appears to be caused by a polyclonal repertoire of T cell accumulation in pancreas without much lymphoid organ involvement and is dependent on the help by B cells.

N-terminal flanking residues of a diabetes-associated GAD65 determinant are necessary for activation of antigen-specific T cells in diabetes-resistant mice

A diabetes-associated peptide in the glutamic acid decarboxylase 65 (GAD65) molecule, p524-543, activates two distinct populations of T cells, which apparently play opposite roles in the development of diabetes in NOD mice. By comparing the fine specificity of these two T cell repertoires using a nested set of truncated peptides that cover the p524-543 region, we found, surprisingly, that all clones recognized the same core within this peptide, p530-539. The core itself was non-immunogenic, but the residues flanking this shared sequence played the crucial role in selecting T cells to activate. A peptide missing N-terminal flanking residues at position 528 and 529 was stimulatory in NOD but not in MHC-matched, NOD-resistant (NOR) mice, suggesting that a protective response in the resistant mice may require T cell recognition of one or more of the N-terminal flanking residues. T cell repertoire studies demonstrated selective clonal expansions within the BV4 TCR family that dominates the p524-543 response in NOD but not in NOR mice. These data suggest that processing or trimming events affecting T cell recognition of very few flanking residues of diabetes-associated determinants might be involved in the protective response in NOR mice.

T cells to a dominant epitope of GAD65 express a public CDR3 motif

Non-obese diabetic (NOD) mice spontaneously develop autoimmune diabetes, and serve as a model for type 1 diabetes (T1D) and natural autoimmunity. T cell responses to the pancreatic islet antigen glutamic acid decarboxylase 65 (GAD65) can be detected in the spleens of young prediabetic NOD mice, which display a unique MHC class II molecule. Here, we report that a distinct TcR beta chain and CDR3 motif are utilized by all NOD mice in response to a dominant determinant on GAD65, establishing a public repertoire in the spontaneous autoimmunity to an important islet cell antigen. GAD65 530-543 (p530)-reactive T cells preferentially utilize the Vbeta4, Dbeta2.1 and Jbeta2.7 gene segments, with a CDR3 that is characterized by a triad of amino acids, DWG, preceded by a polar residue. In addition, we used CDR3 length spectratyping, CDR3-specific reverse transcriptase-PCR and direct TcR sequencing to show that the TcR beta chain structural patterns associated with p530-specific T cells consistently appeared in the islets of young NOD mice with insulitis, but not in the inflamed islets of streptozotocin-treated C57BL/6 mice, or in inflamed NOD salivary glands. To our knowledge, this is the first report to demonstrate that a public T cell repertoire is used in spontaneous autoimmunity to a dominant self-determinant. These findings suggest that defined clonotypes and repertoires may be preferentially selected in haplotypes predisposed to spontaneous autoimmunity.

Restricted islet-cell reactive T cell repertoire of early pancreatic islet infiltrates in NOD mice

The mechanisms responsible for initiating autoimmune diabetes remain obscure. Here, we describe a method for identifying both the alpha- and beta-chains of the T cell receptor (TCR) from individual pancreatic islet-infiltrating T cells at the earliest stages of disease in nonobese diabetic mice (NOD). Analysis of the TCR repertoire of these early islet infiltrates reveals enrichment for a small subset of TCR sequences. Reconstitution of these TCR in vitro demonstrates that these receptors confer reactivity to islet cells but not to the well characterized autoantigens, glutamic acid decarboxylase (GAD65) and insulin. Thus, autoimmune diabetes in NOD may be initiated by a limited number of antigens distinct from GAD65 and insulin.

On the role of the pre-T cell receptor in alphabeta versus gammadelta T lineage commitment

The role of the pre-T cell receptor (TCR) in lineage commitment to the gammadelta versus alphabeta lineage of T cells was addressed by analyzing TCRbeta chain rearrangements in gammadelta T cells from wild-type and pre-TCR-deficient mice by single cell polymerase chain reaction. Results show that the pre-TCR selects against gammadelta T cells containing rearranged Vbeta genes and that gammadelta T cell precursors but not gammadelta T cells express the pre-TCRalpha protein. Furthermore, pre-TCR-induced proliferation could not be detected in gammadelta T cells. We propose that the pre-TCR commits developing T cells to the alphabeta lineage by an instructive mechanism that has largely replaced an evolutionary more ancient stochastic mechanism of lineage commitment.

T-cell receptor Vbeta gene expression in experimental lupus nephritis

A limited T-cell receptor (TCR) Vbeta repertoire employed by autoreactive T cells may be related to the development and course of autoimmune diseases. Vbeta repertoire skewing has been observed not only in man, but also in animal models of several human autoimmune diseases, such as MRL-lpr mice, which spontaneously develop a systemic lupus erythematosus (SLE)-like disease. Murine chronic graft-versus-host disease (GVHD) is an inducible model for SLE, involving direct interaction between donor T cells and recipient B cells. It is not known whether Vbeta-specific T-cell subsets are pathogenically involved in this model. Retroviral superantigens such as Mls-1 are known to have a profound impact on the TCR Vbeta repertoire in mice. Restriction of the peripheral TCR repertoire may result from intrathymic expression of Mls-1, which causes deletion of T cells expressing Vbeta6, -7, -8.1, or -9. Mls-1 incompatibility between donor and recipient can be used to determine the involvement of these TCR Vbeta families in GVHD. In the present study we induced GVHD in several strain combinations to investigate TCR Vbeta gene expression during GVHD, and the effect of Mls-1 incompatibility on the TCR Vbeta repertoire. TCR Vbeta gene expression was determined using an RNase protection assay. Our results indicate that T cells expressing the Vbeta2 or Vbeta16 chain play an important pathogenetic role, while T cells bearing the Vbeta1 or Vbeta6 chain may be related to self-limitation of the lupus-like disease in this model.

Individuals from multiplex insulin-dependent diabetes mellitus (IDDM) families express higher levels of TCRBV2S1 than controls

T lymphocytes recognise peptide antigens through the T cell antigen receptor, which is composed of variable alpha and beta chains. There are forty-six functional variable regions on the beta chain. In this study the expression of the T cell receptor beta-chain variable regions 2S1 and 3S1, in a large cohort of multiplex insulin-dependent diabetes mellitus families, have been determined by use of monoclonal antibodies and flow cytometry. Peripheral blood was collected from these multiplex families and three control groups, healthy individuals, sporadic insulin-dependent diabetes mellitus patients and non-insulin-dependent diabetes mellitus patients. The level of TCRBV2S1 expression in the multiplex families was significantly higher than all the control groups for both the CD4+ and CD8+ T lymphocyte subsets. Detailed analysis of the family data showed that this increased expression was not associated with age, sex, HLA type or the diabetic phenotype. The TCRBV3S1 expression in all the diabetic cohorts was significantly lower than the healthy controls, in the CD4 subset only. Detailed analysis of the family data showed only the fathers TCRBV3S1 expression was lower than the healthy controls. This study gives further insight into TCRBV usage which could reflect the mechanism of the autoimmune response in IDDM multiplex families.

Th1-like cytokine production profile and individual specific alterations in TCRBV-gene usage of T cells from newly diagnosed type 1 diabetes patients after stimulation with beta-cell antigens

In order to study cytokine production profile (IFN-gamma, IL-4 and TNF-alpha) and TCRBV-gene usage of peripheral autoreactive T cells from IDDM patients, we have generated antigen-specific T cell lines with either tetanus toxoid, insulinoma membranes or a single beta-cell protein, recombinant ICA69, which has been shown to be a target of both autoantibodies and T cells in IDDM. By semi-quantitative polymerase chain reaction (PCR) analysis, we have determined the composition of the T cell receptor repertoire of these T cell lines and compared this with the general peripheral repertoire. T cell responses against beta-cell antigens and tetanus toxoid (TT) were shown to be associated with IFN-gamma and TNF-alpha production, suggestive of a Th1-like phenotype of the T-cell lines. The production of IFN-gamma was significantly higher in T-cell lines generated with ISG compared to those generated with TT. The cytokine production profiles of the T-cell lines generated with ICA69 did not provide an obvious explanation for the inverse relation between cellular and humoral responses to this protein observed earlier. Upon stimulation with beta-cell antigens, outgrowth of T cells using a restricted set of TCRBV elements was observed in newly diagnosed IDDM patients. However, this skewing in TCRBV-gene expression was patient-specific rather than antigen-associated, since the T-cell repertoire that is used for the recognition of these antigens was, overall, heterogeneous.

T cell receptor gene polymorphisms associated with anti-insulin, autoimmune T cells in diabetes-prone NOD mice

The great majority of insulin-specific T cell clones isolated from islets of NOD mice react with insulin peptide B-(9-23) (amino acids 9-23 of the insulin B chain). The T cell receptors of these clones contain diverse beta-chains but restricted alpha-chains. The dominant alpha-chain motif is a V alpha 13 segment (10 out of 13) combined to either a J alpha 45 or a J alpha 34 segment (eight out of 13). Furthermore, nine out of 10 of these V alpha 13 segments are a product of a novel NOD TCR V alpha gene which we have termed V alpha 13.3. Analysis of V alpha 13 transcripts from splenic cDNA libraries from the NOD, BALB/c and C57BL/6 mice revealed significant differences between strains. The NOD sequences contained both V alpha 13.1 and the novel V alpha 13.3. The BALB/c contained the previously reported V alpha 13.1 and V alpha 13.2, but not the V alpha 13.3 sequence identified in the NOD anti-insulin T cell clones. The C57BL/6 had V alpha 13.1 and V alpha 13.3 plus two additional novel sequences which we have termed V alpha 13.4 and V alpha 13.5. These V alpha 13 subfamily members differed by two to four amino acids in either the CDR1 region or adjoining the CDR2 region. The frequency of utilization of the different V alpha 13 subtypes varied dramatically between strains. In the NOD spleen, V alpha 13.3 was detected 79% of the time, compared to 21% for V alpha 13.1. In contrast, the C57BL/6 spleen contained only 7% of V alpha 13.3 sequences compared to the other subfamily members present (V alpha 13.1: 27%; V alpha 13.4: 56%; V alpha 13.5: 10%). MHC polymorphisms or other unknown selective pressures may contribute to these differences in V alpha 13 utilization. We hypothesize that the presence and frequent utilization of the V alpha 13.3 T cell receptor element is involved in targeting insulin B-(9-23) and may be related to diabetes susceptibility of NOD mice.

Characterization of T cell receptor repertoire and anti-Ro/SSA autoantibodies in relation to sialadenitis of NOD mice

Non-obese diabetic (NOD) mice develop sialadenitis which morphologically resembles the exocrinopathy in human Sjögren's syndrome (SS). The sialadenitis is characterized by focal infiltrates of inflammatory cells. Immunoenzyme staining (ABC-technique) and monoclonal antibodies defining CD4, CD8, CD11b, TCR alpha/beta, gamma/delta, V beta 2, V beta 4, V beta 6, V beta 7, V beta 8.1, 2, V beta 10b and V beta 11 were used to examine the infiltrating mononuclear cells (MNC) in salivary glands of NOD mice. TCR alpha beta + cells dominated clearly over TCR gamma delta + cells in the salivary glands. A predominance of CD4+ T-cells was identified, while a small population of CD8+ cells was found in the salivary gland infiltrates. CD11b+ mononuclear cells were sporadically seen within the salivary gland lesions. All different TCR V beta:s which were analysed appeared to be utilized at the site of MNC infiltration in salivary glands; although with various frequencies. The frequency pattern of V beta gene expression in salivary glands was V beta 8.1,2 (15%) > V beta 6 (12%) > V beta 4 (11%) > V beta 10b (5%) > V beta 11 (5%) = V beta 2 (5%) > V beta 7 (3%). Analysis of the TCR V beta utilization in corresponding lymph nodes revealed a quite similar frequency pattern as found in the salivary glands. Serum samples were also tested for anti-Ro52, Ro60 and anti-La antibodies with Western blot. Autoantibody production was limited to anti-Ro/SSA and 3/37 (8%) of the mice were found to produce anti-Ro52 kD antibodies. The degree of sialadenitis (focus score) appeared not to influence reactivity to the Ro52 kD protein.