Hugh O. McDevitt

Insulin-Dependent Diabetes Mellitus

Early attempts to prevent IDDM typically relied on immunosuppressive drugs (cyclosporine) or drugs that indiscriminantly inhibit cell proliferation (imuran), often leading to serious side effects. Therefore, a great deal of effort has focused on selectively targeting those T cells involved in the disease process. One general approach has been to employ monoclonal antibodies specific for molecules expressed by the effector T cell population. Monoclonal antibodies specific for CD4 (Shizuru et al. 1988xImmunotherapy of the nonobese diabetic mouse; treatment with an antibody to T helper lymphocytes. Shizuru, J.A, Taylor-Edwards, C, Banks, B.A, Gregory, A.K, and Fathman, C.G. Science. 1988; 240: 659–662Crossref | PubMedSee all ReferencesShizuru et al. 1988) and CD3, a component of TCRs (Chatenoud et al. 1993xAnti-CD3 antibody induces long-term remission of overt autoimmunity in nonobese diabetic mice. Chatenoud, L, Thervet, E, Primo, J, and Bach, J.F. Proc. Natl. Acad. Sci. USA. 1993; 91: 123–127Crossref | Scopus (456)See all ReferencesChatenoud et al. 1993), have been shown to be effective in the prevention and treatment, respectively, of diabetes in NOD mice. Similarly, prediabetic NOD mice are protected from disease when treated with antibodies that interfere with antigen recognition (anti-class II, Boitard et al. 1988xPrevention of diabetes in nonobese diabetic mice by anti- I-A monoclonal antibodies (transfer of protection by splenic T cells) . Boitard, C, Bendelac, A, Richard, M.F, Carnaud, C, and Bach, J.F. Proc. Natl. Acad. Sci. USA. 1988; 85: 9719–9723Crossref | PubMedSee all ReferencesBoitard et al. 1988; anti-TCR, Sempe et al. 1991xAnti-α/β T cell receptor monoclonal antibody provides an efficient therapy for autoimmune diabetes in nonobese diabetic (NOD) mice. Sempe, P, Bedossa, P, Richard, M.F, Villa, M.C, Bach, J.F, and Boitard, C. Eur. J. Immunol. 1991; 21: 1163–1169Crossref | PubMedSee all ReferencesSempe et al. 1991), cellular activation (anti-B7; Lenschow et al. 1995xDifferential effects of anti-B7-1 and anti-B7-2 monoclonal treatment on the development of diabetes in the nonobese diabetic mouse. Lenschow, D.J, Ho, S.C, Sattar, H, Rhee, L, Gray, G, Nabavi, N, Herold, K.C, and Bluestone, J.A. J. Exp. Med. 1995; 181: 1145–1155Crossref | PubMed | Scopus (528)See all ReferencesLenschow et al. 1995), and homing to the pancreas (anti–L selectin and anti-VLA-4; Yang et al. 1993xInhibition of insulitis and prevention of diabetes in nonobese diabetic mice by blocking L-selectin and very late antigen 4 adhesion receptors. Yang, X.D, Karin, N, Tisch, R, Steinman, L, and McDevitt, H.O. Proc. Natl. Acad. Sci. USA. 1993; 90: 10494–10498Crossref | PubMedSee all ReferencesYang et al. 1993). Finally, antibodies targeting cytokines associated with Th1 activity (anti-IFNγ, anti-TNFα, and anti-IL-12; Rabinovitch 1994xImmunoregulatory and cytokine imbalances in the pathogenesis of IDDM. Therapeutic intervention by immunostimulation. Rabinovitch, A. Diabetes. 1994; 43: 613–621Crossref | PubMedSee all ReferencesRabinovitch 1994) have been able to prevent disease in prediabetic NOD mice. In general, however, the applicability of antibodies specific for these “immune–related molecules” to human IDDM is limited by the side effects of chronic administration, such as immunogenicity, and the lack of selectivity.An alternative approach is to devise protocols in which immunomodulation can be selectively applied through the use of a specific antigen/peptide. Recently, it has been demonstrated that insulin, when adminstered prior to the onset of diabetes, can delay or prevent disease in individuals at high risk for IDDM (Keller et al. 1993xInsulin prophylaxis in individuals at high risk of type I diabetes. Keller, R.J, Eisenbarth, G.S, and Jackson, R.A. Lancet. 1993; 341: 927–928Abstract | PubMed | Scopus (261)See all ReferencesKeller et al. 1993). The precise mechanism by which protection is mediated is not known. Both metabolic and immunologic factors may contribute to the effectiveness of this form of therapy. Nevertheless, multicenter trials of subcutaneous insulin prophylaxis to individuals at high risk for developing diabetes have recently been initiated.In general, antigen-specific tolerance can be induced via two distinct processes: clonal deletion/anergy and induction of regulatory T cells. Clonal deletion/anergy has been shown to be effective in acute experimental autoimmune diseases where the inciting autoantigen/peptide is known. However, the high degree of specificity associated with this approach might be limiting in IDDM, in which the inciting autoantigen is not known, and where spreading of the autoimmune response to a number of epitopes within a single autoantigen and targeting of other autoantigens occur. Despite these reservations, administration of GAD, insulin, or HSP60 (but not carboxypeptidase H or peripherin) to NOD mice appears to result in the induction of antigen-specific regualtory T cells (Th2) that effectively suppress the disease. These regulatory T cells are thought to suppress the effects of nearby diabetogenic T cells through the antigen-stimulated secretion of IL-4, IL-10, and TGFβ. The advantage of this approach is that knowledge of the inciting β cell autoantigen (if only one such antigen truly exists) is not required. However, it is still unclear whether regimens can be devised that effectively induce a long lasting form of active suppression with no deleterious side effects in a clinical setting. For example, oral administration of antigen appears to be nontoxic, but its effects are variable and dose specific. This does not appear to be the case with systemically administered antigen. However, the possibility exists that systemic administration of antigen might have an immunizing effect and exacerbate disease.Although antigen-specific immunotherapy appears to be a promising method to prevent IDDM, it is most likely that a combination of approaches may prove to be more generally effective. Thus, active suppression by antigen-induced regulatory T cells may be enhanced in concert with antibodies targeting cytokines required for Th1 development and function. Furthermore, as additional β cell autoantigens are identified and shown to have a role in the disease process, therapy might employ a number of autoantigens to target the polyclonal population of autoreactive T cells, thereby increasing the likelihood of successful treatment.Even if safe, effective, and long lasting immunotherapies are developed, their application is a formidable challenge. Only 15% of new cases of IDDM occur in families with a previous case in the kindred. Overt diabetes develops only when β cell destruction is nearly complete, and the patient is asymptomatic for months or years until that point is reached. Immunotherapy thus must be preventive, which requires inexpensive, accurate genetic, autoantibody, and T cell screening techniques. Given the large number of islet cell autoantigens now available and the rapid progress in identifying genetic susceptibility markers, such screening techniques should soon be feasible. Hopefully, effective methods of prevention will promote widespread population screening and the application of preventive therapy.

Th1 and Th2 CD4+ T cells in the pathogenesis of organ-specific autoimmune diseases

CD4+ T cells play a key role in regulating immune system function. When these regulatory processes go awry, organ-specific autoimmune diseases may develop. Here, Roland Liblau, Steven Singer and Hugh McDevitt explore the thesis that a particular subset of CD4+ T cells, namely T helper 1 (Th1) cells, contributes to the pathogenesis of organ-specific autoimmune diseases, while another subset, Th2 cells, prevents them.

In Vitro–expanded Antigen-specific Regulatory T Cells Suppress Autoimmune Diabetes

The low number of CD4+ CD25+ regulatory T cells (Tregs), their anergic phenotype, and diverse antigen specificity present major challenges to harnessing this potent tolerogenic population to treat autoimmunity and transplant rejection. In this study, we describe a robust method to expand antigen-specific Tregs from autoimmune-prone nonobese diabetic mice. Purified CD4+ CD25+ Tregs were expanded up to 200-fold in less than 2 wk in vitro using a combination of anti-CD3, anti-CD28, and interleukin 2. The expanded Tregs express a classical cell surface phenotype and function both in vitro and in vivo to suppress effector T cell functions. Most significantly, small numbers of antigen-specific Tregs can reverse diabetes after disease onset, suggesting a novel approach to cellular immunotherapy for autoimmunity.

Limited heterogeneity of T cell receptors from lymphocytes mediating autoimmune encephalomyelitis allows specific immune intervention

Experimental allergic encephalomyelitis (EAE) is an induced autoimmune disease mediated by CD4+ T lymphocytes. Analysis of T cell receptors of myelin basic protein-specific encephalitogenic T cell clones derived from six different PL/J (H-2u) or (PL/J x SJL) F1 (H-2uxs) mice revealed a limited heterogeneity in primary structure. In vivo, the majority of T lymphocytes recognize the N-terminal MBP-nonapeptide in association with I-Au and utilize the V beta 8 gene element. cDNA-sequencing showed that all T cell receptors from a panel of such T cell clones, grown in vitro, share the same V alpha gene segment. Despite heterogeneity in the D-J regions, the clones unexpectedly display a striking similarity in fine specificity. Based on these results, prevention and reversal of autoimmune disease with V beta 8-specific monoclonal antibodies was achieved.

Genetic Control of the Antibody Response: Relationship between Immune Response and Histocompatibility (H-2) Type

The immune responses of inbred mice to a related series of three synthetic polypeptide antigens are genetically controlled traits which are closely correlated with the genotype for the major histocompatibility (H-2) locus. All strains of the same H-2 type exhibit the same pattern of immune response, independent of the remainder of a given strains genetic background. There is marked antigen-specific polymorphism between strains of different H-2 types with respect to their patterns of response.

A role for non-MHC genetic polymorphism in susceptibility to spontaneous autoimmunity

Peripheral immunological tolerance is traditionally explained by mechanisms for deletion or inactivation of autoreactive T cell clones. Using an autoimmune disease model combining transgenic mice expressing a well-defined antigen, influenza hemagglutinin (HA), on islet beta cells (Ins-HA), and a T cell receptor transgene (TCR-HNT) specific for a class II-restricted HA peptide, we demonstrate that the conventional assumptions do not apply to this in vivo situation. Double transgenic mice displayed either resistance or susceptibility to spontaneous autoimmune disease, depending on genetic contributions from either of two common inbred mouse strains, BALB/c or B10.D2. Functional studies on autoreactive CD4+ T cells from resistant mice showed that, contrary to expectations, neither clonal anergy, clonal deletion, nor receptor desensitization was induced; rather, there was a non-MHC-encoded predisposition toward differentiation to a nonpathogenic effector (Th2 versus Th1) phenotype. T cells from resistant double transgenic mice showed evidence for prior activation by antigen, suggesting that disease may be actively suppressed by autoreactive Th2 cells. These findings shed light on functional aspects of genetically determined susceptibility to autoimmunity, and should lead to new therapeutic approaches aimed at controlling the differentiation of autoreactive CD4+ effector T cells in vivo.

The Roles of Fas/APO-1 (CD95) and TNF in Antigen-Induced Programmed Cell Death in T Cell Receptor Transgenic Mice

The possible involvement of Fas/APO-1 (CD95) and TNF in antigen-specific AICD of thymocytes and mature T cells has been investigated. Antigenic stimulation in vivo of influenza hemagglutinin (HA)-specific TCRtg mice was used to demonstrate that the kinetics of thymocyte and peripheral CD4+ T cell deletion are similar in mice with normal (+/+) or defective Fas (lpr/lpr) background, indicating that a Fas-independent pathway(s) is responsible for the deletion of activated T cells. TCRtg-+/+ or TCRtg-lpr/lpr mice injected with murine TNF-blocking MAb (TN3) showed rapid apoptosis of thymocytes after HA stimulation, indicating that death signaling through Fas and TNF receptors is not essential for HA-induced thymocyte deletion. CDC peripheral T cells in TCRtg-lpr/lpr mice did not undergo apoptosis following injection with HA and TN3, indicating that TNF-mediated apoptosis is involved in the deletion of mature T cells after antigenic stimulation. However, apoptosis still occurred in TCRtg-+/+ mice injected with TN3, indicating that both Fas- and TNF-mediated cell death can contribute to the deletion of activated peripheral T cells.

Insulin-Dependent Diabetes Mellitus: The Initial Lesion

SUFFICIENT evidence has accumulated over the past decade to allow the statement that insulin-requiring, or insulin-dependent, diabetes mellitus (IDDM; also known as juvenile-onset, Type I, ketosis-...

Tumor necrosis factor-α regulation of CD4+C25+T cell levels in NOD mice

The mechanism by which tumor necrosis factor-α (TNF) differentially modulates type I diabetes mellitus in the nonobese diabetic (NOD) mouse is not well understood. CD4+CD25+ T cells have been implicated as mediators of self-tolerance. We show (i) NOD mice have a relative deficiency of CD4+CD25+ T cells in thymus and spleen; (ii) administration of TNF or anti-TNF to NOD mice can modulate levels of this population consistent with their observed differential age-dependent effects on diabetes in the NOD mouse; (iii) CD4+CD25+ T cells from NOD mice treated neonatally with TNF show compromised effector function in a transfer system, whereas those treated neonatally with anti-TNF show no alteration in ability to prevent diabetes; and (iv) repeated injection of CD4+CD25+ T cells into neonatal NOD mice delays diabetes onset for as long as supplementation occurred. These data suggest that alterations in the number and function of CD4+CD25+ T cells may be one mechanism by which TNF and anti-TNF modulate type I diabetes mellitus in NOD mice.

Expansion of Functional Endogenous Antigen-Specific CD4+CD25+ Regulatory T Cells from Nonobese Diabetic Mice

CD4+CD25+Foxp3+ regulatory T cells (Treg) are critical for controlling autoimmunity. Evidence suggests that Treg development, peripheral maintenance, and suppressive function are dependent on Ag specificity. However, there is little direct evidence that the Treg responsible for controlling autoimmunity in NOD mice or other natural settings are Ag specific. In fact, some investigators have argued that polyclonal Ag-nonspecific Treg are efficient regulators of immunity. Thus, the goal of this study was to identify, expand, and characterize islet Ag-specific Treg in NOD mice. Ag-specific Treg from NOD mice were efficiently expanded in vitro using IL-2 and beads coated with recombinant islet peptide mimic-MHC class II and anti-CD28 mAb. The expanded Ag-specific Treg expressed prototypic surface markers and cytokines. Although activated in an Ag-specific fashion, the expanded Treg were capable of bystander suppression both in vitro and in vivo. Importantly, the islet peptide mimic-specific Treg were more efficient than polyclonal Treg in suppressing autoimmune diabetes. These results provide a direct demonstration of the presence of autoantigen-specific Treg in the natural setting that can be applied as therapeutics for organ-specific autoimmunity.