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.

IL-13Rα1 expression on β-cell-specific T cells in NOD mice.

Objective: Immunotherapy using peptides from the β-cell antigen GAD65 can preserve glucose homeostasis in diabetes-prone NOD mice; however, the precise mechanisms that arrest islet-reactive T cells remain unresolved. Our previous work revealed that a dominant GAD65 epitope contained two overlapping I-A(g7)-restricted determinants, 524-538 and 530-543, with the former associated with amelioration of hyperglycemia. Here, we sought to discover whether p524-538-specific T cells could directly regulate islet-reactive T cells.

Treatment combining RU486 and Ad5IL-12 vector attenuates the growth of experimentally formed prostate tumors and induces changes in the sentinel lymph nodes of mice.

Background: Tumor immune responses are first generated and metastases often begin in tumor sentinel lymph nodes (TSLN). Therefore, it is important to promote tumor immunity within this microenvironment. Mifepristone (RU486) treatment can interfere with cortisol signaling that can lead to suppression of tumor immunity.

Molecular mimics can induce a nonautoaggressive repertoire that preempts induction of autoimmunity.

To determine the role that competition plays in a molecular mimic's capacity to induce autoimmunity, we studied the ability of naïve encephalitogenic T cells to expand in response to agonist altered peptide ligands (APLs), some capable of stimulating both self-directed and exclusively APL-specific T cells. Our results show that although the APLs capable of stimulating exclusively APL-specific T cells are able to expand encephalitogenic T cells in vitro, the encephalitogenic repertoire is effectively outcompeted in vivo when the APL is used as the priming immunogen. Competition as a mechanism was supported by: (i) the demonstration of a population of exclusively APL-specific T cells, (ii) an experiment in which an encephalitogenic T cell population was successfully outcompeted by adoptively transferred naïve T cells, and (iii) demonstrating that the elimination of competing T cells bestowed an APL with the ability to expand naïve encephalitogenic T cells in vivo.

Antigen processing patterns determine GAD65-specific regulation vs. pathogenesis.

Alterations in presenting self determinants to T cells may depend upon the availability of sites on the molecule adjacent to known determinants to different processing enzymes, or, at the level of amino acid sequence or conformation of a single determinant. We have studied three possible ways that could modulate the processing and presentation of T cell determinants of a diabetes autoantigen, glutamic acid decarboxylase (GAD) 65, which could contribute to induction of GAD65-specific regulatory versus pathogenic T cells in type 1 diabetes (T1D): 1) enhanced presentation of subdominant/cryptic determinants to T cells that have not been well-tolerized, which may activate T cells of high affinity and high aggressiveness; 2) trimming or truncating flanking residues which may otherwise provide needed binding energy to determinants that activate regulatory cells, thus releasing autoaggressive T cells from suppression; 3) biochemical or chemical modifications of self antigens in an inflammatory environment or within activated antigen presenting cells (APC) which may convert a previously regulatory antigen or determinant into a disease-causing one that activates autoreactive T cells at a higher affinity.

Altered peptide ligands can modify the Th2 T cell response to the immunodominant 161-175 peptide of LACK (Leishmania homolog for the receptor of activated C kinase).

Following Leishmania major infection, the early LACK (Leishmania homolog of receptors for activated C kinase)-induced IL-4 response appears to determine disease susceptibility in BALB/c mice. Therefore, we sought to manipulate the pathogenic T cell responses to the immunodominant epitope with the use of altered peptide ligands (APLs). Conservative and non-conservative substitutions for each amino acid of the LACK 161-175 peptide determinant were tested for their stimulatory capacity in four different LACK-reactive T cell systems.

Slc11a1 enhances the autoimmune diabetogenic T-cell response by altering processing and presentation of pancreatic islet antigens.

Objective: Efforts to map non-major histocompatibility complex (MHC) genes causing type 1 diabetes in NOD mice identified Slc11a1, formerly Nramp1, as the leading candidate gene in the Idd5.2 region. Slc11a1 is a membrane transporter of bivalent cations that is expressed in late endosomes and lysosomes of macrophages and dendritic cells (DCs).

Administration of PLP139-151 primes T cells distinct from those spontaneously responsive in vitro to this antigen.

We examined the TCR repertoire used by naive SJL mice in their in vitro spontaneous response to proteolipid protein (PLP) 139-151 by Vbeta-Jbeta spectratyping and compared it to that used after immunization with the peptide. T cells from immunized mice use the public rearrangement Vbeta10-Jbeta1.1, but naive mice do not; in contrast, TCR CDR3-beta rearrangements of Vbeta18-Jbeta1.

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.

Presentation of a determinant by MHC class II can be prevented through competitive capture by a flanking determinant on a multideterminant peptide.

Competitive capture is a process by which different determinants of an unfolding antigen compete for binding to the same MHC class II molecule. The "winning" determinant is then dominantly displayed. For self antigens, T cells with specificity for dominantly displayed determinants will be subject to strong tolerance induction.

Immunodominance in the TCR repertoire of a [corrected] TCR peptide-specific CD4+ Treg population that controls experimental autoimmune encephalomyelitis.

Immunodominance in self-Ag-reactive pathogenic CD4(+) T cells has been well established in several experimental models. Although it is clear that regulatory lymphocytes (Treg) play a crucial role in the control of autoreactive cells, it is still not clear whether immunodominant CD4(+) Treg clones are also involved in control of autoreactivity. We have shown that TCR-peptide-reactive CD4(+) and CD8(+) Treg play an important role in the spontaneous recovery and resistance from reinduction of experimental autoimmune encephalomyelitis in B10.

On the pathogenicity of autoantigen-specific T-cell receptors.

Objective: Type 1 diabetes is mediated by T-cell entry into pancreatic islets and destruction of insulin-producing beta-cells. The relative contribution of T-cells specific for different autoantigens is largely unknown because relatively few have been assessed in vivo.

Research Design And Methods: We generated mice possessing a monoclonal population of T-cells expressing 1 of 17 T-cell receptors (TCR) specific for either known autoantigens (GAD65, insulinoma-associated protein 2 (IA2), IA2beta/phogrin, and insulin), unknown islet antigens, or control antigens on a NOD.

Etiology of autoimmune disease: how T cells escape self-tolerance.

Despite central and peripheral regulatory mechanisms designed to prevent self-reactivity, autoimmune disease is a common condition. This article explores several ways in which both high and low affinity T cells can avoid negative selection. The concept of intramolecular sequestration indicates that there will be a hierarchy of presentation of different antigenic determinants derived from a protein antigen, such that some determinants will be efficiently presented whereas others will be poorly presented or not presented at all.

A public T cell clonotype within a heterogeneous autoreactive repertoire is dominant in driving EAE.

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis. Immunization of B10.PL mice with the Ac1-9 peptide, the immunodominant determinant of myelin basic protein (MBP), produced a single episode of EAE followed by recovery and resistance to reinduction of disease.

Polyspecificity of T cell and B cell receptor recognition.

A recent workshop discussed the recognition of multiple distinct ligands by individual T cell and B cell receptors and the implications of this discovery for lymphocyte biology. The workshop recommends general use of the term polyspecificity because it emphasizes two fundamental aspects, the inherent specificity of receptor recognition and the ability to recognize multiple ligands. Many different examples of polyspecificity and the structural mechanisms were discussed, and the group concluded that polyspecificity is a general, inherent feature of TCR and antibody recognition.

Attenuation of the glucocorticoid response during Ad5IL-12 adenovirus vector treatment enhances natural killer cell-mediated killing of MHC class I-negative LNCaP prostate tumors.

Tumor cells can evolve to evade immune responses by down-modulating surface MHC class I expression and become refractory to T cell-directed immunotherapy. We employed a strategy to bypass this escape mechanism using a recombinant adenovirus vector expressing interleukin-12 (Ad5IL-12) to target natural killer (NK) cell-mediated killing of human prostate tumors in NOD.scid mice.

TAP1-/- mice present oligoclonal BV-BJ expansions following the rejection of grafts bearing self antigens.

Our previous work showed that transporter associated with antigen processing 1 (TAP1)-/- (H-2b) mice rejected grafts from H-2b mice which display a normal density of class I major histocompatibility complex (MHC) molecules at the cell surface. Our results indicated that H-2b molecules themselves may be a target in this kind of rejection and that CD4+ T cells play a major role in this autoreactive process. Our data also suggested that TAP1-/- mice, in addition to the well-recognized phenotype of class I and CD8+ T-cell deficiency, present a functional alteration in their autoreactive CD4+ T-cell repertoires.

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.

Antigen processing by autoreactive B cells promotes determinant spreading.

Acute primary immune responses tend to focus on few immunodominant determinants using a very limited number of T cell clones for expansion, whereas chronic inflammatory responses generally recruit a large number of different T cell clones to attack a broader range of determinants of the invading pathogens or the inflamed tissues. In T cell-mediated organ-specific autoimmune disease, a transition from the acute to the chronic phase contributes to pathogenesis, and the broadening process is called determinant spreading. The cellular components catalyzing the spreading reaction are not identified.

A peptide of glutamic acid decarboxylase 65 can recruit and expand a diabetogenic T cell clone, BDC2.5, in the pancreas.

Self peptide-MHC ligands create and maintain the mature T cell repertoire by positive selection in the thymus and by homeostatic proliferation in the periphery. A low affinity/avidity interaction among T cells, self peptides, and MHC molecules has been suggested for these events, but it remains unknown whether or how this self-interaction is involved in tolerance and/or autoimmunity. Several lines of evidence implicate the glutamic acid decarboxylase 65 (GAD-65) peptide, p524-543, as a specific, possibly low affinity, stimulus for the spontaneously arising, diabetogenic T cell clone BDC2.

Crypticity of self antigenic determinants is the cornerstone of a theory of autoimmunity.

Extract: The immune system is designed to keep in check, to kill, and to clear from the body any invading disease-causing microbial agents such as bacteria and viruses. This immunity against foreign pathogens is mediated primarily through T lymphocytes and antibodies. Furthermore, there are in-built regulatory mechanisms that monitor the activity of these immune effector components.

Feedback regulation of autoimmunity via TCR-centered regulation.

The complexity of a self-regulatory system demands a balance between effectors and regulators; that is, it is necessary for both cell types to exist. Regulation of self-reactive T cells can occur at several complementary but different levels: (1) at the level of priming itself: for example, inhibition of expansion of antigen-reactive T cells by regulatory CD4+ CD25+ T cells; (2) after the priming of self-reactive T cells, regulatory T-cell populations with reactivity to distinct self-determinants derived from the T-cell receptor (TCR) can be engaged via a negative feedback mechanism. Thus, these mechanisms ensure induction of effective and appropriately limited responses against foreign antigens while preventing autoreactivity from inflicting self-damage.

Understanding crypticity is the key to revealing the pathogenesis of autoimmunity.

In this opinion, we propose that the hierarchy of antigenic determinants within self-antigens is the major influence in molding the potentially autoreactive T-cell repertoire. The well processed and presented determinants constitute a 'dominant self', whereas the poorly processed and/or presented determinants will be invisible to T cells and comprise a 'cryptic self', which we consider a fundamental cornerstone of a theory of autoimmunity. It accounts for the large repertoire of self-reactive clones because a similar hierarchy is established in the thymus and controls positive and negative selection.

Clustering of T cell ligands on artificial APC membranes influences T cell activation and protein kinase C theta translocation to the T cell plasma membrane.

T cell activation is associated with active clustering of relevant molecules in membrane microdomains defined as the supramolecular activation cluster. The contact area between these regions on the surface of T cells and APC is defined as the immunological synapse. It has been recently shown that preclustering of MHC-peptide complexes in membrane microdomains on the APC surface affects the efficiency of immune synapse formation and the related T cell activation.

Skewed T-cell receptor BV14 and BV16 expression and shared CDR3 sequence and common sequence motifs in synovial T cells of rheumatoid arthritis.

T-lymphocytes play an important role in rheumatoid arthritis (RA). In this study, we evaluated the hypothesis that common T-cell receptor (TCR) structural features may exist among infiltrating T cells of different RA patients, if the TCR repertoire is shaped by interaction with common self or microbial antigens in the context of susceptible HLA genes in RA. Synovial lesion tissue (ST), synovial fluid (SF) and blood specimens from RA patients and controls were analyzed for TCR V gene repertoire by real-time PCR.