Faecal microbiota transplantation halts progression of human new-onset type 1 diabetes in a randomised controlled trial.

OBJECTIVE: Type 1 diabetes (T1D) is characterised by islet autoimmunity and beta cell destruction. A gut microbiota-immunological interplay is involved in the pathophysiology of T1D. We studied microbiota-mediated effects on disease progression in patients with type 1 diabetes using faecal microbiota transplantation (FMT). DESIGN: Patients with recent-onset (<6 weeks) T1D (18-30 years of age) were randomised into two groups to receive three autologous or allogenic (healthy donor) FMTs over a period of 4 months. Our primary endpoint was preservation of stimulated C peptide release assessed by mixed-meal tests during 12 months. Secondary outcome parameters were changes in glycaemic control, fasting plasma metabolites, T cell autoimmunity, small intestinal gene expression profile and intestinal microbiota composition. RESULTS: Stimulated C peptide levels were significantly preserved in the autologous FMT group (n=10 subjects) compared with healthy donor FMT group (n=10 subjects) at 12 months. Small intestinal Prevotella was inversely related to residual beta cell function (r=-0.55, p=0.02), whereas plasma metabolites 1-arachidonoyl-GPC and 1-myristoyl-2-arachidonoyl-GPC levels linearly correlated with residual beta cell preservation (rho=0.56, p=0.01 and rho=0.46, p=0.042, respectively). Finally, baseline CD4 +CXCR3+T cell counts, levels of small intestinal Desulfovibrio piger and CCL22 and CCL5 gene expression in duodenal biopsies predicted preserved beta cell function following FMT irrespective of donor characteristics. CONCLUSION: FMT halts decline in endogenous insulin production in recently diagnosed patients with T1D in 12 months after disease onset. Several microbiota-derived plasma metabolites and bacterial strains were linked to preserved residual beta cell function. This study provides insight into the role of the intestinal gut microbiome in T1D. TRIAL REGISTRATION NUMBER: NTR3697.

Oral butyrate does not affect innate immunity and islet autoimmunity in individuals with longstanding type 1 diabetes: a randomised controlled trial.

AIMS/HYPOTHESIS: The pathophysiology of type 1 diabetes has been linked to altered gut microbiota and more specifically to a shortage of intestinal production of the short-chain fatty acid (SCFA) butyrate, which may play key roles in maintaining intestinal epithelial integrity and in human and gut microbial metabolism. Butyrate supplementation can protect against autoimmune diabetes in mouse models. We thus set out to study the effect of oral butyrate vs placebo on glucose regulation and immune variables in human participants with longstanding type 1 diabetes. METHODS: We administered a daily oral dose of 4 g sodium butyrate or placebo for 1 month to 30 individuals with longstanding type 1 diabetes, without comorbidity or medication use, in a randomised (1:1), controlled, double-blind crossover trial, with a washout period of 1 month in between. Participants were randomly allocated to the 'oral sodium butyrate capsules first' or 'oral placebo capsules first' study arm in blocks of five. The clinical investigator received blinded medication from the clinical trial pharmacy. All participants, people doing measurements or examinations, or people assessing the outcomes were blinded to group assignment. The primary outcome was a change in the innate immune phenotype (monocyte subsets and in vitro cytokine production). Secondary outcomes were changes in blood markers of islet autoimmunity (cell counts, lymphocyte stimulation indices and CD8 quantum dot assays), glucose and lipid metabolism, beta cell function (by mixed-meal test), gut microbiota and faecal SCFA. The data was collected at the Amsterdam University Medical Centers. RESULTS: All 30 participants were analysed. Faecal butyrate and propionate levels were significantly affected by oral butyrate supplementation and butyrate treatment was safe. However, this modulation of intestinal SCFAs did not result in any significant changes in adaptive or innate immunity, or in any of the other outcome variables. In our discussion, we elaborate on this important discrepancy with previous animal work. CONCLUSIONS/INTERPRETATION: Oral butyrate supplementation does not significantly affect innate or adaptive immunity in humans with longstanding type 1 diabetes. TRIAL REGISTRATION: Netherlands Trial Register: NL4832 (www.trialregister.nl). DATA AVAILABILITY: Raw sequencing data are available in the European Nucleotide Archive repository (https://www.ebi.ac.uk/ena/browse) under study PRJEB30292. FUNDING: The study was funded by a Le Ducq consortium grant, a CVON grant, a personal ZONMW-VIDI grant and a Dutch Heart Foundation grant.

Type 1 diabetes induction in humanized mice.

There is an urgent and unmet need for humanized in vivo models of type 1 diabetes to study immunopathogenesis and immunotherapy, and in particular antigen-specific therapy. Transfer of patient blood lymphocytes to immunodeficient mice is associated with xenogeneic graft-versus-host reactivity that complicates assessment of autoimmunity. Improved models could identify which human T cells initiate and participate in beta-cell destruction and help define critical target islet autoantigens. We used humanized mice (hu-mice) containing robust human immune repertoires lacking xenogeneic graft-versus-host reactivity to address this question. Hu-mice constructed by transplantation of HLA-DQ8+ human fetal thymus and CD34+ cells into HLA-DQ8-transgenic immunodeficient mice developed hyperglycemia and diabetes after transfer of autologous HLA-DQ8/insulin-B:9-23 (InsB:9-23)-specific T-cell receptor (TCR)-expressing human CD4+ T cells and immunization with InsB:9-23. Survival of the infused human T cells depended on the preexisting autologous human immune system, and pancreatic infiltration by human CD3+ T cells and insulitis were observed in the diabetic hu-mice, provided their islets were stressed by streptozotocin. This study fits Koch's postulate for pathogenicity, demonstrating a pathogenic role of islet autoreactive CD4+ T-cell responses in type 1 diabetes induction in humans, underscores the role of the target beta-cells in their immunological fate, and demonstrates the capacity to initiate disease with T cells, recognizing the InsB:9-23 epitope in the presence of islet inflammation. This preclinical model has the potential to be used in studies of the pathogenesis of type 1 diabetes and for testing of clinically relevant therapeutic interventions.

Identification of Donor Origin and Condition of Transplanted Islets In Situ in the Liver of a Type 1 Diabetic Recipient.

Transplantation of islet allografts into type 1 diabetic recipients usually requires multiple pancreas donors to achieve insulin independence. This adds to the challenges of immunological monitoring of islet transplantation currently relying on surrogate immune markers in peripheral blood. We investigated donor origin and infiltration of islets transplanted in the liver of a T1D patient who died of hemorrhagic stroke 4 months after successful transplantation with two intraportal islet grafts combining six donors. Immunohistological staining for donor HLA using a unique panel of human monoclonal HLA-specific alloantibodies was performed on liver cryosections after validation on cryopreserved kidney, liver, and pancreas and compared with auto- and alloreactive T-cell immunity in peripheral blood. HLA-specific staining intensity and signal-to-noise ratio varied between tissues from very strong on kidney glomeruli, less in liver, kidney tubuli, and endocrine pancreas to least in exocrine pancreas, complicating the staining of inflamed islets in an HLA-disparate liver. Nonetheless, five islets from different liver lobes could be attributed to donors 1, 2, and 5 by staining patterns with multiple HLA types. All islets showed infiltration with CD8+ cytotoxic T cells that was mirrored by progressive alloreactive responses in peripheral blood mononuclear cells (PBMCs) to donors 1, 2, and 5 after transplantation. Stably low rates of peripheral islet autoreactive T-cell responses after islet infusion fit with a complete HLA mismatch between grafts and recipient and exclude the possibility that the islet-infiltrating CD8 T cells were autoreactive. HLA-specific immunohistochemistry can identify donor origin in situ and differentiate graft dysfunction and immunological destruction.

Immunogenicity of human embryonic stem cell-derived beta cells.

AIMS/HYPOTHESIS: To overcome the donor shortage in the treatment of advanced type 1 diabetes by islet transplantation, human embryonic stem cells (hESCs) show great potential as an unlimited alternative source of beta cells. hESCs may have immune privileged properties and it is important to determine whether these properties are preserved in hESC-derived cells. METHODS: We comprehensively investigated interactions of both innate and adaptive auto- and allo-immunity with hESC-derived pancreatic progenitor cells and hESC-derived endocrine cells, retrieved after in-vivo differentiation in capsules in the subcutis of mice. RESULTS: We found that hESC-derived pancreatic endodermal cells expressed relatively low levels of HLA endorsing protection from specific immune responses. HLA was upregulated when exposed to IFNγ, making these endocrine progenitor cells vulnerable to cytotoxic T cells and alloreactive antibodies. In vivo-differentiated endocrine cells were protected from complement, but expressed more HLA and were targets for alloreactive antibody-dependent cellular cytotoxicity and alloreactive cytotoxic T cells. After HLA compatibility was provided by transduction with HLA-A2, preproinsulin-specific T cells killed insulin-producing cells. CONCLUSIONS/INTERPRETATION: hESC-derived pancreatic progenitors are hypoimmunogenic, while in vivo-differentiated endocrine cells represent mature targets for adaptive immune responses. Our data support the need for immune intervention in transplantation of hESC-derived pancreatic progenitors. Cell-impermeable macro-encapsulation may suffice.

Innate and adaptive immunity to human beta cell lines: implications for beta cell therapy.

AIMS/HYPOTHESIS: Genetically engineered human beta cell lines provide a novel source of human beta cells to study metabolism, pharmacology and beta cell replacement therapy. Since the immune system is essentially involved in beta cell destruction in type 1 diabetes and after beta cell transplantation, we investigated the interaction of human beta cell lineswith the immune system to resolve their potential for immune intervention protocol studies. METHODS: Human pancreatic beta cell lines (EndoC-ßH1 and ECi50) generated by targeted oncogenesis in fetal pancreas were assessed for viability after innate and adaptive immune challenges. Beta cell lines were pre-conditioned with T helper type 1 (Th1) cytokines or high glucose to mimic inflammatory and hyperglycaemia-stressed conditions. Beta cells were then co-cultured with auto- and alloreactive cytotoxic T cells (CTL), natural killer (NK) cells, supernatant fraction from activated autoreactive Th1 cells, or alloantibodies in the presence of complement or effector cells. RESULTS: Low HLA expression protected human beta cell lines from adaptive immune destruction, but it was associated with direct killing by activated NK cells. Autoreactive Th1 cell inflammation, rather than glucose stress, induced increased beta cell apoptosis and upregulation of HLA, increasing beta cell vulnerability to killing by auto- and alloreactive CTL and alloreactive antibodies. CONCLUSIONS/INTERPRETATION: We demonstrate that genetically engineered human beta cell lines can be used in vitro to assess diverse immune responses that may be involved in the pathogenesis of type 1 diabetes in humans and beta cell transplantation, enabling preclinical evaluation of novel immune intervention strategies protecting beta cells from immune destruction.

T cell receptor reversed polarity recognition of a self-antigen major histocompatibility complex.

Central to adaptive immunity is the interaction between the αß T cell receptor (TCR) and peptide presented by the major histocompatibility complex (MHC) molecule. Presumably reflecting TCR-MHC bias and T cell signaling constraints, the TCR universally adopts a canonical polarity atop the MHC. We report the structures of two TCRs, derived from human induced T regulatory (iT(reg)) cells, complexed to an MHC class II molecule presenting a proinsulin-derived peptide. The ternary complexes revealed a 180° polarity reversal compared to all other TCR-peptide-MHC complex structures. Namely, the iT(reg) TCR α-chain and ß-chain are overlaid with the α-chain and ß-chain of MHC class II, respectively. Nevertheless, this TCR interaction elicited a peptide-reactive, MHC-restricted T cell signal. Thus TCRs are not 'hardwired' to interact with MHC molecules in a stereotypic manner to elicit a T cell signal, a finding that fundamentally challenges our understanding of TCR recognition.

Posttranslational modification of HLA-DQ binding islet autoantigens in type 1 diabetes.

Posttranslational modification (PTM) of islet autoantigens can cause lack of central tolerance in type 1 diabetes (T1D). Tissue transglutaminase (tTG), involved in PTM of gluten antigens in celiac disease, creates negatively charged peptides favored by T1D-predisposing HLA-DQ molecules, offering an attractive candidate modifying islet autoantigens in T1D. The highly predisposing HLA-DQ8cis/trans molecules share preferences for negatively charged peptides, as well as distinct peptide-binding characteristics that distinguish their peptide-binding repertoire. We screened islet autoantigens with the tTG substrate motif for candidate-modified epitopes binding to HLA-DQ8cis/trans and identified 31 candidate islet epitopes. Deamidation was confirmed for 28 peptides (90%). Two of these epitopes preferentially bound to HLA-DQ8cis and six to HLA-DQ8trans upon deamidation, whereas all other peptides bound equally to HLA-DQ8cis/trans. HLA-DQ8cis-restricted T cells from a new-onset T1D patient could only be generated against a deamidated proinsulin peptide, but cross-reacted with native proinsulin peptide upon restimulation. The rate of T-cell autoreactivity in recent-onset T1D patients extended from 42% to native insulin to 68% adding responses to modified proinsulin, versus 20% and 37% respectively, in healthy donors. Most patients responded by interferon-γ, whereas most healthy donors produced interleukin-10 only. Thus, T-cell autoreactivity exists to modified islet epitopes that differs in quality and quantity between patients and healthy donors.

Transfer of regulatory properties from tolerogenic to proinflammatory dendritic cells via induced autoreactive regulatory T cells.

Infectious tolerance is a term generally assigned to the process through which regulatory T cells (Tregs) transfer immunoregulatory properties to other T cells. In this study, we demonstrated that a similar process applies to human dendritic cells (DCs), albeit through a different mechanism. We induced and cloned proinsulin-specific Tregs using tolerogenic DCs and investigated mechanisms by which induced Ag-specific regulatory T cells (iaTregs) endorse the suppressive effects. iaTregs expressed FOXP3, programmed death-1, and membrane-bound TGF-ß and upregulated IL-10 and CTLA-4 after stimulation with the cognate Ag. The iaTregs suppressed effector T cells only when both encountered the cognate Ags on the same APCs (linked suppression). This occurred independently of IL-10, TGF-ß, programmed death-1, or CTLA-4. Instead, iaTregs used a granzyme B-mediated mechanism to kill B cells and monocytes, whereas proinflammatory DCs that resisted being killed were induced to upregulate the inhibitory receptors B7 (family) homolog 3 and ICOS ligand. These re-educated mature monocyte-derived dendritic cells (mDCs) suppressed effector T cells and induced IL-10-producing cells from the naive T cell pool. Our data indicated that human tolerogenic DCs confer infectious tolerance by inducing Ag-specific Tregs, which, in turn, re-educate proinflammatory mature DCs into DCs with regulatory properties.

Discovery of low-affinity preproinsulin epitopes and detection of autoreactive CD8 T-cells using combinatorial MHC multimers.

Autoreactive cytotoxic CD8 T-cells (CTLs) play a key pathogenic role in the destruction of insulin-producing beta-cells resulting in type 1 diabetes. However, knowledge regarding their targets is limited, restricting the ability to monitor the course of the disease and immune interventions. In a multi-step discovery process to identify novel CTL epitopes in human preproinsulin (PPI), PPI was digested with purified human proteasomes, and resulting COOH-fragments aligned with algorithm-predicted HLA-binding peptides to yield nine potential HLA-A1, -A2, -A3 or -B7-restricted candidates. An UV-exchange method allowed the generation of a repertoire of multimers including low-affinity HLA-binding peptides. These were labeled with quantum dot-fluorochromes and encoded in a combinatorial fashion, allowing parallel and sensitive detection of specific, low-avidity T-cells. Significantly increased frequencies of T-cells against four novel PPI epitopes (PPI(4-13)/B7, PPI(29-38)/A2, PPI(76-84)/A3 and PPI(79-88)/A3) were detected in stored blood of patients with recent onset diabetes but not in controls. Changes in frequencies of circulating CD8 T-cells against these novel epitopes were detected in blood of islet graft recipients at different time points after transplantation, which correlated with clinical outcome. In conclusion, our novel strategy involving a sensitive multiplex detection technology and requiring minimal volumes of stored blood represents a major improvement in the direct ex-vivo characterization and enumeration of immune cells in the pathogenesis of type 1 diabetes.

Critical role for TNF in the induction of human antigen-specific regulatory T cells by tolerogenic dendritic cells.

TNF is a pleiotropic cytokine with differential effects on immune cells and diseases. Anti-TNF therapy was shown to be effective in rheumatoid arthritis but proved inefficient or even detrimental in other autoimmune diseases. We studied the role of TNF in the induction of Ag-specific regulatory T cells (Tregs) by tolerogenic vitamin D3-modulated human dendritic cells (VD3-DCs), which previously were shown to release high amounts of soluble TNF (sTNF) upon maturation with LPS. First, production of TNF by modulated VD3-DCs was analyzed upon maturation with LPS or CD40L with respect to both secreted (cleaved) TNF (sTNF) and expression of the membrane-bound (uncleaved) form of TNF (mTNF). Next, TNF antagonists were tested for their effect on induction of Ag-specific Tregs by modulated DCs and the subsequent functionality of these Tregs. VD3-DCs expressed greater amounts of mTNF than did control DCs (nontreated DCs), independent of the maturation protocol. Inhibition of TNF with anti-TNF Ab (blocking both sTNF and mTNF) during the priming of Tregs with VD3-DCs prevented generation of Tregs and their suppression of proliferation of CD4(+) T cells. In contrast, sTNF receptor II (sTNFRII), mainly blocking sTNF, did not change the suppressive capacity of Tregs. Blocking of TNFRII by anti-CD120b Ab during Treg induction similarly abrogated their subsequent suppressive function. These data point to a specific role for mTNF on VD3-DCs in the induction of Ag-specific Tregs. Interaction between mTNF and TNFRII instructs the induction of suppressive Tregs by VD3-DCs. Anti-TNF therapy may therefore act adversely in different patients or disease pathways.

Simultaneous detection of circulating autoreactive CD8+ T-cells specific for different islet cell-associated epitopes using combinatorial MHC multimers.

OBJECTIVE: Type 1 diabetes results from selective T-cell-mediated destruction of the insulin-producing beta-cells in the pancreas. In this process, islet epitope-specific CD8(+) T-cells play a pivotal role. Thus, monitoring of multiple islet-specific CD8(+) T-cells may prove to be valuable for measuring disease activity, progression, and intervention. Yet, conventional detection techniques (ELISPOT and HLA tetramers) require many cells and are relatively insensitive. RESEARCH DESIGN AND METHODS: Here, we used a combinatorial quantum dot major histocompatibility complex multimer technique to simultaneously monitor the presence of HLA-A2 restricted insulin B(10-18), prepro-insulin (PPI)(15-24), islet antigen (IA)-2(797-805), GAD65(114-123), islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(265-273), and prepro islet amyloid polypeptide (ppIAPP)(5-13)-specific CD8(+) T-cells in recent-onset diabetic patients, their siblings, healthy control subjects, and islet cell transplantation recipients. RESULTS: Using this kit, islet autoreactive CD8(+) T-cells recognizing insulin B(10-18), IA-2(797-805), and IGRP(265-273) were shown to be frequently detectable in recent-onset diabetic patients but rarely in healthy control subjects; PPI(15-24) proved to be the most sensitive epitope. Applying the "Diab-Q-kit" to samples of islet cell transplantation recipients allowed detection of changes of autoreactive T-cell frequencies against multiple islet cell-derived epitopes that were associated with disease activity and correlated with clinical outcome. CONCLUSIONS: A kit was developed that allows simultaneous detection of CD8(+) T-cells reactive to multiple HLA-A2-restricted beta-cell epitopes requiring limited amounts of blood, without a need for in vitro culture, that is applicable on stored blood samples.

Cellular islet autoimmunity associates with clinical outcome of islet cell transplantation.

BACKGROUND: Islet cell transplantation can cure type 1 diabetes (T1D), but only a minority of recipients remains insulin-independent in the following years. We tested the hypothesis that allograft rejection and recurrent autoimmunity contribute to this progressive loss of islet allograft function. METHODOLOGY/PRINCIPAL FINDINGS: Twenty-one T1D patients received cultured islet cell grafts prepared from multiple donors and transplanted under anti-thymocyte globulin (ATG) induction and tacrolimus plus mycophenolate mofetil (MMF) maintenance immunosuppression. Immunity against auto- and alloantigens was measured before and during one year after transplantation. Cellular auto- and alloreactivity was assessed by lymphocyte stimulation tests against autoantigens and cytotoxic T lymphocyte precursor assays, respectively. Humoral reactivity was measured by auto- and alloantibodies. Clinical outcome parameters--including time until insulin independence, insulin independence at one year, and C-peptide levels over one year--remained blinded until their correlation with immunological parameters. All patients showed significant improvement of metabolic control and 13 out of 21 became insulin-independent. Multivariate analyses showed that presence of cellular autoimmunity before and after transplantation is associated with delayed insulin-independence (p = 0.001 and p = 0.01, respectively) and lower circulating C-peptide levels during the first year after transplantation (p = 0.002 and p = 0.02, respectively). Seven out of eight patients without pre-existent T-cell autoreactivity became insulin-independent, versus none of the four patients reactive to both islet autoantigens GAD and IA-2 before transplantation. Autoantibody levels and cellular alloreactivity had no significant association with outcome. CONCLUSIONS/SIGNIFICANCE: In this cohort study, cellular islet-specific autoimmunity associates with clinical outcome of islet cell transplantation under ATG-tacrolimus-MMF immunosuppression. Tailored immunotherapy targeting cellular islet autoreactivity may be required. Monitoring cellular immune reactivity can be useful to identify factors influencing graft survival and to assess efficacy of immunosuppression. TRIAL REGISTRATION: Clinicaltrials.gov NCT00623610.

Alloreactivity against repeated HLA mismatches of sequential islet grafts transplanted in non-uremic type 1 diabetes patients.

BACKGROUND: Islet transplantation can restore insulin production in type 1 diabetes patients. However, survival of the islet allografts will face rejection or recurrence of autoimmunity or a combination of both. In a study on islet-after-kidney transplants, we previously reported that islet cell recipients presented low T-cell alloresponses for HLA mismatches that were shared by the islet cell graft and the prior kidney graft, that is, repeated mismatch, while vigorous responses were measured against novel HLA mismatches. METHODS: We now investigated T-cell alloreactivity to repeated HLA-mismatches in three non-uremic type 1 diabetic patients each receiving three sequential islet cell implants. RESULTS: These islet-after-islet recipients patients exhibited low or absent responses to repeated mismatches to the first graft which was accompanied by sustained graft function, and reduced responsiveness towards subsequent grafts. In one patient, T-cell responses towards these mismatches were noticed following new mismatches in subsequent grafts, with loss of graft function. CONCLUSION: These case reports further support the view that subsequent islet implantations can reduce alloreactivity for repeated HLA mismatches. They demonstrate the usefulness of monitoring T-cell reactivity against islet allografts to correlate immune function with graft survival and to identify conditions for preservation of beta-cell function.

HLA incompatibility and immunogenicity of human pancreatic islet preparations cocultured with blood cells of healthy donors.

Type 1 diabetes mellitus (T1D) is a T-cell-mediated autoimmune disease characterized by the destruction of beta cells in the pancreas. An attractive novel therapy for type 1 diabetes is pancreatic islet transplantation, provided that recurrent islet autoimmunity and allograft rejection can be prevented. We analyzed the response of peripheral blood mononuclear cells (PBMC) from healthy blood donors to human islet-cell preparations with a composition similar to that of islet grafts used in clinical transplantation trials. It was examined whether the degree of major histocompatibility complex incompatibility between PBMC and donor islet cells is related to the degree of proliferative T-cell responses during coculture of human leukocyte antigen (HLA)-matched and mismatched PBMC with human islet cell-preparations (i.e., mixed islet/lymphocyte reaction). Prominent T-cell responses were observed in the vast majority of cases of double HLA class II mismatches. Intermediate T-cell responsiveness was observed in single HLA class II mismatches, whereas HLA matches did not induce a T-cell response. Our results identify the potential immunogenicity of islet preparations transplanted between HLA-DR incompatible subjects regardless of an autoimmune background of the recipient.

Precursor frequencies of T-cells reactive to insulin in recent onset type 1 diabetes mellitus.

T-cell mediated autoimmune beta-cell destruction is an important component of type 1 diabetes (T1D) and insulin is a critical antigen recognized by autoreactive T-cells. The aim of this study was to investigate the precursor frequency of insulin reactive T-cells in type 1 diabetes. We studied 19 T1D patients, 12 age-matching non-diabetic healthy siblings and 12 non-diabetic healthy parents. Limiting dilution analysis (LDA) was performed to insulin and tetanus toxoid (TT). A progressive decrease in the number of negative cultures at increasing cell concentrations that is represented by a low goodness-of-fit (GoF, low Chi-square), was seen with the TT response in all three groups; precursor frequencies and GoF were similar in patients, siblings, and parents. Reactivity to insulin, however, showed low precursor frequencies in patients and siblings and the LDA to insulin demonstrated dramatic decreases in the number of positive cultures at higher cell concentrations leading to a high GoF in patients and siblings compared to parents. This saw-toothed pattern of reactivity to insulin is indicative of multiple hit kinetics and implies that the response is regulated. Consequently the precursor frequency of insulin autoreactive cells in patients and their siblings is probably much higher than calculated.

HLA-DQ-regulated T-cell responses to islet cell autoantigens insulin and GAD65.

HLA-DQ is strongly associated with genetic predisposition to type 1 diabetes. It is assumed that HLA-DQ molecules exert their effects on the disease via the presentation of peptides from islet autoantigens to CD4(+) T-cells, but little information regarding HLA-DQ-restricted, islet antigen-specific, autoreactive T-cells is available. To investigate the role of HLA-DQ in the immune response to islet autoantigens, we measured T-cell proliferation to insulin and GAD65 in the presence and absence of monoclonal antibodies that block HLA-DQ-mediated antigen presentation in recent-onset type 1 diabetic patients and their siblings. Positive proliferative T-cell responses to GAD65 were observed in 60% of type 1 diabetic patients and 52% of siblings. This proliferation was significantly reduced in the presence of anti-DQ antibody, demonstrating the presence of primed, effector HLA-DQ-restricted T-cell responses to GAD65. Positive proliferative responses to insulin were observed in 25% of type 1 diabetic patients and 10% of siblings. However, blocking HLA-DQ-restricted T-cell responses led to a significant increase in proliferation to insulin, implying the presence of primed suppressive HLA-DQ-restricted T-cell responses to insulin. These results indicate that HLA-DQ acts as a restriction element for both proliferative and suppressor cells, with the relative balance of these cells dependent on the nature of the autoantigen.