An important role of CD80/CD86-CTLA-4 signaling during photocarcinogenesis in mice.

Although previous studies have shown that altered B7 costimulation plays a critical role in UV irradiation-induced regulation of immunity, the individual roles of the B7 receptors (CD28 and CTLA-4) or the B7 family members (CD80 and CD86) have not been explored. Thus, we investigated CTLA-4 signaling during photocarcinogenesis of chronically UV-B-exposed mice using an antagonistic anti-CTLA-4 Ab. Anti-CTLA-4-treated mice developed significantly fewer UV-induced tumors.

Distinct roles of dendritic cells and B cells in Va14Ja18 natural T cell activation in vivo.

Va14Ja18 natural T (iNKT) cells are innate, immunoregulatory lymphocytes that recognize CD1d-restricted lipid Ags such as alpha-galactosylceramide (alpha GalCer). The immunoregulatory functions of iNKT cells are dependent upon either IFN-gamma or IL-4 production by these cells. We hypothesized that alpha GalCer presentation by different CD1d-positive cell types elicits distinct iNKT cell functions.

Treatment with nonmitogenic anti-CD3 monoclonal antibody induces CD4+ T cell unresponsiveness and functional reversal of established experimental autoimmune encephalomyelitis.

In vivo administration of anti-CD3 Ab induces both immune tolerance and undesirable side-effects resulting from nonspecific proinflammatory cytokine production. In the current study, we investigated the therapeutic potential of two structurally altered forms of the anti-CD3 Ab in ameliorating established experimental autoimmune encephalomyelitis. Administration of either a chimeric (NM-IgG3) or digestion product (NM-F(ab')2) form of the anti-CD3 Ab during established experimental autoimmune encephalomyelitis conferred significant protection from clinical disease progression and was associated with decreased Ag-specific T cell proliferation, cytokine production, and CNS inflammation.

Regulatory T-cell therapy: is it ready for the clinic?

The identification of suppressor T cells as important regulators of basic processes that are designed to maintain tolerance has opened an important area of potential clinical investigation in autoimmunity, graft-versus-host disease and transplantation. However, the field has been limited by an inability to define the antigenic specificities of these cells and by the small numbers of circulating regulatory T cells. Recently, new methods for expanding polyclonal and antigen-specific regulatory T cells have emerged.

The NOD mouse: a model of immune dysregulation.

Autoimmunity is a complex process that likely results from the summation of multiple defective tolerance mechanisms. The NOD mouse strain is an excellent model of autoimmune disease and an important tool for dissecting tolerance mechanisms. The strength of this mouse strain is that it develops spontaneous autoimmune diabetes, which shares many similarities to autoimmune or type 1a diabetes (T1D) in human subjects, including the presence of pancreas-specific autoantibodies, autoreactive CD4+ and CD8+ T cells, and genetic linkage to disease syntenic to that found in humans.

Distinct roles of CTLA-4 and TGF-beta in CD4+CD25+ regulatory T cell function.

Both CTLA-4 and TGF-beta have been implicated in suppression by CD4+CD25+ regulatory T cells (Treg). In this study, the relationship between CTLA-4 and TGF-beta in Treg function was examined. Blocking CTLA-4 on wild-type Treg abrogated their suppressive activity in vitro, whereas neutralizing TGF-beta had no effect, supporting a TGF-beta-independent role for CTLA-4 in Treg-mediated suppression in vitro.

Costimulation controls diabetes by altering the balance of pathogenic and regulatory T cells.

The development of autoimmune diabetes in the nonobese diabetic (NOD) mouse results from a breakdown in tolerance to pancreatic islet antigens. CD28-B7 and CD40 ligand-CD40 (CD40L-CD40) costimulatory pathways affect the development of disease and are promising therapeutic targets. Indeed, it was shown previously that diabetes fails to develop in NOD-B7-2-/- and NOD-CD40L-/- mice.

Peptide specific amelioration of T cell mediated pathogenesis in murine type 1 diabetes.

NOD mice spontaneously develop insulitis and type 1 diabetes (T1D) mellitus similar to humans. Insulitis without overt disease occurs in the BDC2.5 TCR-transgenic NOD mice that express the rearranged TCR alpha- and beta-chain genes of a diabetogenic T cell clone reactive to an unknown beta cell autoantigen.

Therapeutic vaccination using CD4+CD25+ antigen-specific regulatory T cells.

Autoimmune disease results from the dysregulation of basic tolerogenic processes designed to control self/non-self-discrimination. Approaches to treat autoimmunity have focused historically on potent immunosuppressives that block the activation and expansion of antigen-specific T cells before they differentiate into pathogenic T cell responses. These therapies are very efficient in reducing clonal expansion and altering early signaling pathways.

NKG2D blockade prevents autoimmune diabetes in NOD mice.

NKG2D is an activating receptor on CD8(+) T cells and NK cells that has been implicated in immunity against tumors and microbial pathogens. Here we show that RAE-1 is present in prediabetic pancreas islets of NOD mice and that autoreactive CD8(+) T cells infiltrating the pancreas express NKG2D. Treatment with a nondepleting anti-NKG2D monoclonal antibody (mAb) during the prediabetic stage completely prevented disease by impairing the expansion and function of autoreactive CD8(+) T cells.

CTLA-4 regulates expansion and differentiation of Th1 cells following induction of peripheral T cell tolerance.

Intravenous treatment with Ag (peptide)-coupled, ethylene carbodiimide-fixed syngeneic splenocytes (Ag-SP) is a powerful method to induce anergy in vitro and peripheral T cell tolerance in vivo. In this study, we examined the effects of Ag-SP administration on T cell activity ex vivo and in vivo using OVA-specific DO11.10 TCR transgenic T cells.

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.

Notch signaling in lymphocyte development and function.

Over the past few years, the crucial role of Notch signaling in multiple stages of T-cell development has become apparent. Recent studies have helped to define more precisely the functions and components of the Notch signaling pathway in T-cell development, including during the T versus B fate decision and in early CD4(-)CD8(-)double-negative thymocytes. In addition, new evidence points to a requirement for Notch2 in the development of marginal zone B cells.

Notch 1 signaling regulates peripheral T cell activation.

Notch signaling has been identified as an important regulator of leukocyte differentiation and thymic maturation. Less is known about the role of Notch signaling in regulating mature T cells. We examined the role of Notch 1 in regulating peripheral T cell activity in vitro and in vivo.

Transplantation of cultured islets from two-layer preserved pancreases in type 1 diabetes with anti-CD3 antibody.

We sought to determine whether or not optimizing pancreas preservation, islet processing, and induction immunosuppression would facilitate sustained diabetes reversal after single-donor islet transplants. Islets were isolated from two-layer preserved pancreata, purified, cultured for 2 days; and transplanted into six C-peptide-negative, nonuremic, type 1 diabetic patients with hypoglycemia unawareness. Induction immunosuppression, which began 2 days pretransplant, included the Fc receptor nonbinding humanized anti-CD3 monoclonal antibody hOKT3gamma1 (Ala-Ala) and sirolimus.

Insulin secretion in type 1 diabetes.

Type 1 diabetes, a chronic autoimmune disease, causes destruction of insulin-producing beta-cells over a period of years. Although many markers of the autoimmune process have been described, none can convincingly predict the rate of disease progression. Moreover, there is relatively little information about changes in insulin secretion in individuals with type 1 diabetes over time.

Beta-cell replacement for type I diabetes.

The ability to achieve insulin independence with either solid-organ pancreas or islet transplantation has increased the number of patients seeking beta-cell replacement as an alternative to insulin therapy. Despite dramatic improvements in the ability to achieve insulin independence following solid-organ pancreas transplantation, the secondary complications of long-standing diabetes are frequently irreversible by the time surgical intervention is justified based on the risk of this procedure. Pancreatic islet transplantation provides a safer and less invasive alternative for beta-cell replacement that could be justified earlier in the course of diabetes to prevent the development of secondary complications.

Importance of IL-10 for CTLA-4-mediated inhibition of tumor-eradicating immunity.

In this study, we show that engagement of CTLA-4 on tumor-infiltrating lymphocytes from low-dose melphalan (L-phenylalanine mustard (L-PAM))-treated MOPC-315 tumor bearers led to IL-10 secretion. In addition, the inhibitory activity of CTLA-4 ligation for IFN-gamma secretion following stimulation with anti-CD3 plus anti-CD28 mAb depended on IL-10 production. Consistent with the importance of IL-10 for CTLA-4-mediated inhibition, administration of neutralizing anti-IL-10 mAb to low-dose L-PAM-treated MOPC-315 tumor bearers (administration of blocking anti-CTLA-4 mAb) resulted in enhanced tumor-infiltrating lymphocyte-mediated anti-MOPC-315 cytotoxicity and led to complete tumor eradication in a higher percentage of mice than that observed with low-dose L-PAM alone.

CTLA-4 and tolerance: the biochemical point of view.

Potentially autoreactive T cells that escape negative selection in the thymus must be strictly controlled in the periphery to avoid autoimmune disease. The most robust regulatory process controlling autoreactivity is mediated by the CTLA-4-B7 pathway. The critical homeostasis mediated by CTLA-4 was proven using monoclonal antibodies and genetically disrupted CTLA-4 knockout mice that develop polyclonal lymphocyte activation and proliferation leading to massively enlarged lymph nodes and spleen and fatal multiorgan lymphocytic infiltrates.

The role of CD28 and CTLA4 in the function and homeostasis of CD4+CD25+ regulatory T cells.

CD4+CD25+ T cells regulate a variety of autoimmune and alloimmune responses including the development of autoimmune diabetes in non-obese diabetic (NOD) mice. We have examined the role of CD28/CTLA4/B7 interactions in the expansion and survival of CD4+CD25+ regulatory T cells (T(reg)) in this setting. CD28/ B7 interactions are essential in the development of T(reg) in the thymus and for their survival in the periphery.

Peptide-MHC class II dimers as therapeutics to modulate antigen-specific T cell responses in autoimmune diabetes.

Type 1 diabetes is an autoimmune disorder caused by autoreactive T cells that mediate destruction of insulin-producing beta cells of the pancreas. Studies have shown that T cell tolerance can be restored by inducing a partial or altered signal through the TCR. To investigate the potential of bivalent peptide-MHC class II/Ig fusion proteins as therapeutics to restore Ag-specific tolerance, we have developed soluble peptide I-A(g7) dimers for use in the nonobese diabetic mouse model of diabetes.

Cutting edge: CD28 controls peripheral homeostasis of CD4+CD25+ regulatory T cells.

CD28/B7 blockade leads to exacerbated autoimmune disease in the nonobese diabetic mouse strain as a result of a marked reduction in the number of CD4(+)CD25(+) regulatory T cells (Tregs). Herein, we demonstrate that CD28 controls both thymic development and peripheral homeostasis of Tregs. CD28 maintains a stable pool of peripheral Tregs by both supporting their survival and promoting their self-renewal.

Targeting and blocking B7 costimulatory molecules on antigen-presenting cells using CTLA4Ig-conjugated liposomes: in vitro characterization and in vivo factors affecting biodistribution.

Purpose: CTLA4Ig, a fusion protein of CTLA-4 and Fc of immunoglobulin (Ig) heavy chain, inhibits the essential costimulatory signal for full T cell activation via blocking the interaction between CD28 and B7 molecules and renders T cell nonresponsiveness. CTLA4Ig has been used to control deleterious T cell activation in many experimental systems. We hypothesized that by conjugating CTLA4Ig to liposomes the efficacy of CTLA4Ig could be enhanced through multivalent ligand effect, superior targetability, and modification of the fate of ligated costimulatory molecules.