Multispecific responses by T cells expanded by endogenous self-peptide/MHC complexes

Studying antigen-specific T cells through a streamlined, whole blood-based extracellular approach

Techniques currently used for the study of antigen-specific T-cell responses are either poorly informative or require a heavy workload. Consequently, many perspectives associated with the broader study of such approaches remain mostly unexplored in translational research. However, these could benefit many fields including but not limited to infectious diseases, oncology, and vaccination. Herein, the main objective of this work was to develop a standardized flow cytometry-based approach that would combine ease of use together with a relevant study of antigen-specific T-cell responses so that they could be more often included in clinical research. To this extent, a streamlined approach relying on 1/ the use of whole blood instead of peripheral blood mononuclear cells and 2/ solely based on the expression of extracellular activation-induced markers (AIMs), called whole blood AIM (WAIM), was developed and further compared to more conventional techniques such as enzyme-linked immunospot (ELISpot) and flow cytometry-based intracellular cytokine staining (ICS). Based on a cohort of 20 individuals receiving the COVID-19 mRNA vaccine and focusing on SARS-CoV-2 and cytomegalovirus (CMV)-derived antigen T-cell-specific responses, a significant level of correlation between the three techniques was found. Based on the use of whole blood and on the expression of extracellular activation-induced markers (CD154, CD137, and CD107a), the WAIM technique appears to be very simple to implement and yet allows interesting patient stratification capabilities as the chosen combination of extracellular markers exhibited higher orthogonality than cytokines that are commonly considered in ICS (IFN-γ, TNF-α, and IL-2).

HLA-DR15 Molecules Jointly Shape an Autoreactive T Cell Repertoire in Multiple Sclerosis

The HLA-DR15 haplotype is the strongest genetic risk factor for multiple sclerosis (MS), but our understanding of how it contributes to MS is limited. Because autoreactive CD4⁺ T cells and B cells as antigen-presenting cells are involved in MS pathogenesis, we characterized the immunopeptidomes of the two HLA-DR15 allomorphs DR2a and DR2b of human primary B cells and monocytes, thymus, and MS brain tissue. Self-peptides from HLA-DR molecules, particularly from DR2a and DR2b themselves, are abundant on B cells and thymic antigen-presenting cells. Furthermore, we identified autoreactive CD4⁺ T cell clones that can cross-react with HLA-DR-derived self-peptides (HLA-DR-SPs), peptides from MS-associated foreign agents (Epstein-Barr virus and Akkermansia muciniphila), and autoantigens presented by DR2a and DR2b. Thus, both HLA-DR15 allomorphs jointly shape an autoreactive T cell repertoire by serving as antigen-presenting structures and epitope sources and by presenting the same foreign peptides and autoantigens to autoreactive CD4⁺ T cells in MS.

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HLA-DR15 present abundant HLA-DR-derived self-peptides on B cells

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Autoreactive T cells in MS recognize HLA-DR-derived self-peptides/DR15 complexes

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Foreign peptides/DR15 complexes trigger potential autoreactive T cells in MS

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HLA-DR15 shape an autoreactive T cell repertoire by cross-reactivity/restriction

Treatment of experimental autoimmune encephalomyelitis with engineered bi-specific Foxp3+ regulatory CD4+ T cells

The use of autoantigen-specific regulatory T cells (Tregs) as a cellular therapy for autoimmune diseases is appealing. However, it is challenging to isolate and expand large quantity of Tregs expressing disease-relevant T-cell receptors (TCR). To overcome this problem, we used an approach aiming at redirecting the specificity of polyclonal Tregs through autoreactive TCR gene transfer technology. In this study, we examined whether Tregs engineered through retroviral transduction to express a TCR cross-reactive to two CNS autoantigens, myelin oligodendrocyte glycoprotein (MOG) and neurofilament-medium (NF-M), had a superior protective efficacy compared with Tregs expressing a MOG mono-specific TCR. We observed that engineered Tregs (engTregs) exhibited in vitro regulatory effects related to the antigenic specificity of the introduced TCR, and commensurate in potency with the avidity of the transduced TCR. In experimental autoimmune encephalomyelitis (EAE), adoptively transferred engTregs proliferated, and migrated to the CNS, while retaining FoxP3 expression. EngTregs expressing MOG/NF-M cross-reactive TCR had superior protective properties over engTregs expressing MOG-specific TCR in MOG-induced EAE. Remarkably, MOG/NF-M bi-specific TCR-engTregs also improved recovery from EAE induced by an unrelated CNS autoantigen, proteolipid protein (PLP). This study underlines the benefit of using TCRs cross-reacting towards multiple autoantigens, compared with mono-reactive TCR, for the generation of engTregs affording protection from autoimmune disease in adoptive cell therapy.

Human CD4+ T Cells Specific for Merkel Cell Polyomavirus Localize to Merkel Cell Carcinomas and Target a Required Oncogenic Domain

Although CD4⁺ T cells likely play key roles in antitumor immune responses, most immuno-oncology studies have been limited to CD8⁺ T-cell responses due to multiple technical barriers and a lack of shared antigens across patients. Merkel cell carcinoma (MCC) is an aggressive skin cancer caused by Merkel cell polyomavirus (MCPyV) oncoproteins in 80% of cases. Because MCPyV oncoproteins are shared across most patients with MCC, it is unusually feasible to identify, characterize, and potentially augment tumor-specific CD4⁺ T cells. Here, we report the identification of CD4⁺ T-cell responses against six MCPyV epitopes, one of which included a conserved, essential viral oncogenic domain that binds/disables the cellular retinoblastoma (Rb) tumor suppressor. We found that this epitope (WED_LT209-228) could be presented by three population-prevalent HLA class II alleles, making it a relevant target in 64% of virus-positive MCC patients. Cellular staining with a WED_LT209-228-HLA-DRB1*0401 tetramer indicated that specific CD4⁺ T cells were detectable in 78% (14 of 18) of evaluable MCC patients, were 250-fold enriched within MCC tumors relative to peripheral blood, and had diverse T-cell receptor sequences. We also identified a modification of this domain that still allowed recognition by these CD4⁺ T cells but disabled binding to the Rb tumor suppressor, a key step in the detoxification of a possible therapeutic vaccine. The use of these new tools for deeper study of MCPyV-specific CD4⁺ T cells may provide broader insight into cancer-specific CD4⁺ T-cell responses.

Memory B Cells Activate Brain-Homing, Autoreactive CD4+ T Cells in Multiple Sclerosis

Multiple sclerosis is an autoimmune disease that is caused by the interplay of genetic, particularly the HLA-DR15 haplotype, and environmental risk factors. How these etiologic factors contribute to generating an autoreactive CD4⁺ T cell repertoire is not clear. Here, we demonstrate that self-reactivity, defined as “autoproliferation” of peripheral Th1 cells, is elevated in patients carrying the HLA-DR15 haplotype. Autoproliferation is mediated by memory B cells in a HLA-DR-dependent manner. Depletion of B cells in vitro and therapeutically in vivo by anti-CD20 effectively reduces T cell autoproliferation. T cell receptor deep sequencing showed that in vitro autoproliferating T cells are enriched for brain-homing T cells. Using an unbiased epitope discovery approach, we identified RASGRP2 as target autoantigen that is expressed in the brain and B cells. These findings will be instrumental to address important questions regarding pathogenic B-T cell interactions in multiple sclerosis and possibly also to develop novel therapies.

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Autoproliferation of CD4⁺ T cells and B cells is involved in multiple sclerosis

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The main genetic factor of MS, HLA-DR15, plays a central role in autoproliferation

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Memory B cells drive autoproliferation of Th1 brain-homing CD4⁺ T cells

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Autoproliferating T cells recognize antigens expressed in B cells and brain lesions

In situ expansion of T cells that recognize distinct self-antigens sustains autoimmunity in the CNS

Polyspecific T cells recognizing multiple distinct self-antigens have been identified in multiple sclerosis and other organ-specific autoimmune diseases, but their pathophysiological relevance remains undetermined. Using a mouse model of multiple sclerosis, we show that autoimmune encephalomyelitis induction is strictly dependent on reactivation of pathogenic T cells by a peptide (35-55) derived from myelin oligodendrocyte glycoprotein (MOG). This disease-inducing response wanes after onset. Strikingly, the progression of disease is driven by the in situ activation and expansion of a minority of MOG35-55-specific T cells that also recognize neurofilament-medium (NF-M)15-35, an intermediate filament protein expressed in neurons. This mobilization of bispecific T cells is critical for disease progression as adoptive transfer of NF-M15-35/MOG35-55 bispecific T cell lines caused full-blown disease in wild-type but not NF-M-deficient recipients. Moreover, specific tolerance through injection of NF-M15-35 peptide at the peak of disease halted experimental autoimmune encephalomyelitis progression. Our findings highlight the importance of polyspecific autoreactive T cells in the aggravation and perpetuation of central nervous system autoimmunity.

Auto-reactive T cells revised. Overestimation based on methodology?

Autoreactive T cells have been identified in most autoimmune diseases and recently even in healthy individuals. Similar, T cells that recognize either wild-type or tumorspecific tumor antigens have been increasingly reported to develop spontaneously in cancer patients. This insight has become possible mainly due to novel immunoassays which have revolutionized the discovery of rare antigen specific T cells. At present, the major dogma that explains this increasing number of reports of autoreactive T cells is that autoreactive T cells are counteracted by CD4+CD25+ regulatory T (Treg) cells in vivo, in particular in healthy individuals, whereas dysfunction in Tregs or Treg responsiveness may unmask the autoreactive T cell responses in patients with autoimmune diseases. However, studies that identify autoreactive T cells are usually performed by culturing T cells with antigen presenting cells loaded with E. coli produced recombinant protein or unmodified synthetic HLA binding peptides. Our concern is that this approach may ignore the presence of natural genetic variation and post-translational modifications such as e.g. the complex nature of N- and O-linked glycosylation of mammalian proteins. Thus, T cell antigen reactivities identified with unmodified antigens in vitro may in part represent in vitro T cell activation against neo-epitopes and not true in vivo autoreactivity as postulated. This methodological problem may have implications for the interpretation of the frequent reporting of autoreactive T cells in autoimmunity, T cell responses to wild-type tumor antigens in cancer patients and most important for the increasing reports on naïve T cells with specificity against self-antigens in healthy individuals. Here, we discuss and provide examples for the possibility that the experimental methodology applied to document T cell reactivity against unmodified protein or peptide may lead to overinterpretation of the reported frequencies of autoreactive CD4+ and CD8+ T cells.

Bispecificity for myelin and neuronal self-antigens is a common feature of CD4 T cells in C57BL/6 mice

The recognition of multiple ligands by a single TCR is an intrinsic feature of T cell biology, with important consequences for physiological and pathological processes. Polyspecific T cells targeting distinct self-antigens have been identified in healthy individuals as well as in the context of autoimmunity. We have previously shown that the 2D2 TCR recognizes the myelin oligodendrocyte glycoprotein epitope (MOG)35-55 as well as an epitope within the axonal protein neurofilament medium (NF-M15-35) in H-2(b) mice. In this study, we assess whether this cross-reactivity is a common feature of the MOG35-55-specific T cell response. To this end, we analyzed the CD4 T cell response of MOG35-55-immunized C57BL/6 mice for cross-reactivity with NF-M15-35. Using Ag recall responses, we established that an important proportion of MOG35-55-specific CD4 T cells also responded to NF-M15-35 in all mice tested. To study the clonality of this response, we analyzed 22 MOG35-55-specific T cell hybridomas expressing distinct TCR. Seven hybridomas were found to cross-react with NF-M15-35. Using an alanine scan of NF-M18-30 and an in silico predictive model, we dissected the molecular basis of cross-reactivity between MOG35-55 and NF-M15-35. We established that NF-M F24, R26, and V27 proved important TCR contacts. Strikingly, the identified TCR contacts are conserved within MOG38-50. Our data indicate that due to linear sequence homology, part of the MOG35-55-specific T cell repertoire of all C57BL/6 mice also recognizes NF-M15-35, with potential implications for CNS autoimmunity.

HLA-DR15-derived self-peptides are involved in increased autologous T cell proliferation in multiple sclerosis

The HLA-DR15 haplotype confers the largest part of the genetic risk to develop multiple sclerosis, a prototypic CD4+ T cell-mediated autoimmune disease. The mechanisms how certain HLA-class II molecules functionally contribute to autoimmune diseases are still poorly understood, but probably involve shaping an autoimmune-prone T cell repertoire during central tolerance in the thymus and subsequently maintaining or even expanding it in the peripheral immune system. Self-peptides that are presented by disease-associated HLA-class II molecules most likely play important roles during both processes. Here, we examined the functional involvement of the HLA-DR15 haplotype in autologous proliferation in multiple sclerosis and the contribution of HLA-DR15 haplotype-derived self-peptides in an in vitro system. We observe increased autologous T cell proliferation in patients with multiple sclerosis in relation to the multiple sclerosis risk-associated HLA-DR15 haplotype. Assuming that the spectrum of self-peptides that is presented by the two HLA-DR15 allelic products is important for sustaining autologous proliferation we performed peptide elution and identification experiments from the multiple sclerosis-associated DR15 molecules and a systematic analysis of a DR15 haplotype-derived self-peptide library. We identify HLA-derived self-peptides as potential mediators of altered autologous proliferation. Our data provide novel insights about perturbed T cell repertoire dynamics and the functional involvement of the major genetic risk factor, the HLA-DR15 haplotype, in multiple sclerosis.

Human CD4(+) effector T lymphocytes generated upon TCR engagement with self-peptides respond defectively to IL-7 in their transition to memory cells

The peripheral repertoire of CD4(+) T lymphocytes contains autoreactive cells that remain tolerant through several mechanisms. However, nonspecific CD4(+) T cells can be activated in physiological conditions as in the course of an ongoing immune response, and their outcome is not yet fully understood. Here, we investigate the fate of human naive CD4(+) lymphocytes activated by dendritic cells (DCs) presenting endogenous self-peptides in comparison with lymphocytes involved in alloresponses. We generated memory cells (Tmem) from primary effectors activated with mature autologous DCs plus interleukin (IL)-2 (Tmauto), simulating the circumstances of an active immune response, or allogeneic DCs (Tmallo). Tmem were generated from effector cells that were rested in the absence of antigenic stimuli, with or without IL-7. Tmem were less activated than effectors (demonstrated by CD25 downregulation) particularly with IL-7, suggesting that this cytokine may favour the transition to quiescence. Tmauto and Tmallo showed an effector memory phenotype, and responded similarly to polyclonal and antigen-specific stimuli. Biochemically, IL-7-treated Tmallo were closely related to conventional memory lymphocytes based on Erk-1/2 activation, whereas Tmauto were more similar to effectors. Autologous effectors exhibited lower responses to IL-7 than allogeneic cells, which were reflected in their reduced proliferation and higher cell death. This was not related to IL-7 receptor expression but rather to signalling deficiencies, according to STAT5 activation These results suggest that ineffective responses to IL-7 could impair the transition to memory cells of naive CD4(+) T lymphocytes recognizing self-peptides in the setting of strong costimulation.

Mammalian lipocalin allergens--insights into their enigmatic allergenicity

Most of the important mammal-derived respiratory allergens, as well as a milk allergen and a few insect allergens, belong to the lipocalin protein family. As mammalian lipocalin allergens are found in dander, saliva and urine, they disperse effectively and are widely present in the indoor environments. Initially, lipocalins were characterized as transport proteins for small, principally hydrophobic molecules, but now they are known to be involved in many other biological functions. Although the amino acid identity between lipocalins is generally at the level of 20-30%, it can be considerably higher. Lipocalin allergens do not exhibit any known physicochemical, functional or structural property that would account for their allergenicity, that is, the capacity to induce T-helper type 2 immunity against them. A distinctive feature of mammalian lipocalin allergens is their poor capacity to stimulate the cellular arm of the human or murine immune system. Nevertheless, they induce IgE production in a large proportion of atopic individuals exposed to the allergen source. The poor capacity of mammalian lipocalin allergens to stimulate the cellular immune system does not appear to result from the function of regulatory T cells. Instead, the T cell epitopes of mammalian lipocalin allergens are few and those examined have proved to be suboptimal. Moreover, the frequency of mammalian lipocalin allergen-specific CD4(+) T cells is very low in the peripheral blood. Importantly, recent research suggests that the lipocalin allergen-specific T cell repertoires differ considerably between allergic and healthy subjects. These observations are compatible with our hypothesis that the way CD4(+) T-helper cells recognize the epitopes of mammalian lipocalin allergens may be implicated in their allergenicity. Indeed, as several lipocalins exhibit homologies of 40-60% over species, mammalian lipocalin allergens may be immunologically at the borderline of self and non-self, which would not allow a strong anti-allergenic immune response against them.

Cumulative autoimmunity: T cell clones recognizing several self-epitopes exhibit enhanced pathogenicity

T cell receptor (TCR) recognition is intrinsically polyspecific. In the field of autoimmunity, recognition of both self- and microbial peptides by a single TCR has led to the concept of molecular mimicry. However, findings made by our group and others clearly demonstrate that a given TCR can also recognize multiple distinct self-peptides. Based on experimental data we argue that recognition of several self-peptides increases the pathogenicity of an autoreactive T cell; a property we refer to as “cumulative autoimmunity.” The mechanisms of such increased pathogenicity, and the implications of cumulative autoimmunity regarding the pathophysiology of T cell-mediated autoimmune diseases will be discussed.

Mycobacterium tuberculosis Beijing genotype induces differential cytokine production by peripheral blood mononuclear cells of healthy BCG vaccinated individuals

Members of the Mycobacterium tuberculosis (Mtb) Beijing genotype are a major concern due to their high prevalence in tuberculosis patients and their high rate of multi-drug resistance. Although it has been shown that Beijing modifies macrophage behavior, little is known about how this genotype could affect the cellular immune response. In order to address this issue, peripheral blood mononuclear cells (PBMC) from healthy BCG vaccinated individuals were stimulated with protein extracts from three Mycobacterium tuberculosis genotypes: Canetti, H37Rv and Beijing evaluating T cell proliferation and cytokine production. In this system both CD4+ and CD8+ proliferated in a similar manner independently of the Mtb genotype used for stimulation. Regarding cytokines, all strains induced similar levels of IFN-γ, but were unable to induce IL-4 and TGF-β. Contrasting, Canetti strain induced lower production of IL-10, TNF-α and IL-12 compared to H37Rv and Beijing. Interestingly, PBMC stimulated with the Beijing strain produced the highest levels of IL-12 and IL-10 than those stimulated with other strains. This differential cytokine expression could affect the pathogenesis induced by Beijing strain through the modulation of inflammatory process in the host, but the precise mechanisms by which this cytokine environment affects the Beijing strain pathogenesis needs further characterization.

CCR6 is expressed on an IL-10-producing, autoreactive memory T cell population with context-dependent regulatory function

Interleukin (IL)-10 produced by regulatory T cell subsets is important for the prevention of autoimmunity and immunopathology, but little is known about the phenotype and function of IL-10–producing memory T cells. Human CD4⁺CCR6⁺ memory T cells contained comparable numbers of IL-17– and IL-10–producing cells, and CCR6 was induced under both Th17-promoting conditions and upon tolerogenic T cell priming with transforming growth factor (TGF)–β. In normal human spleens, the majority of CCR6⁺ memory T cells were in the close vicinity of CCR6⁺ myeloid dendritic cells (mDCs), and strikingly, some of them were secreting IL-10 in situ. Furthermore, CCR6⁺ memory T cells produced suppressive IL-10 but not IL-2 upon stimulation with autologous immature mDCs ex vivo, and secreted IL-10 efficiently in response to suboptimal T cell receptor (TCR) stimulation with anti-CD3 antibodies. However, optimal TCR stimulation of CCR6⁺ T cells induced expression of IL-2, interferon-γ, CCL20, and CD40L, and autoreactive CCR6⁺ T cell lines responded to various recall antigens. Notably, we isolated autoreactive CCR6⁺ T cell clones with context-dependent behavior that produced IL-10 with autologous mDCs alone, but that secreted IL-2 and proliferated upon stimulation with tetanus toxoid. We propose the novel concept that a population of memory T cells, which is fully equipped to participate in secondary immune responses upon recognition of a relevant recall antigen, contributes to the maintenance of tolerance under steady-state conditions.

Degenerate T-cell receptor recognition, autoreactive cells, and the autoimmune response in multiple sclerosis

Multiple sclerosis (MS) is the leading cause of disability in the young adult population. While the immunopathogenetic mechanisms that drive the disease have been extensively studied, the autoantigens that trigger the chronic central nervous system inflammation are still not identified. Flexibility/ degeneracy of the T-cell receptor (TCR) in antigen recognition could have a physiological role in thymic selection and the development of comprehensive TCR repertoire and protection from infections. Here, the author explores the possibility that such flexibility/degeneracy may also play a role in the induction of autoimmune diseases. Major histocompatibility complex (MHC) class II alleles of the DR2 haplotype DR2a (DRB5*0101) and DR2b (DRB1*1501) are genes associated with an increased risk for MS in Caucasian populations. Peptide binding to the MHC molecule is a prerequisite for recognition by TCRs, whereby the CD4+ T-cell response is restricted by specific MHC class II DR molecules. To selectively expand and characterize DR2-restricted T-cells with degenerate TCR (TCR(deg)), the authors designed MHC class II DR2-anchored peptide mixtures, which preferentially bind to the DR2a and DR2b antigen-presenting molecules. Peptides in these mixtures have specific amino acids in the DR2 binding positions but have randomized amino acids at all other positions of the peptide. Due to the low concentration of individual peptides in these mixtures/libraries, the authors assume that only T-cells with TCR(deg) will proliferate in response to these mixtures. The authors have recently identified an increased DR2 restricted TCR(deg) T-cell frequency in MS patients in comparison to healthy controls, their cross-reactivity to myelin basic protein, and the secretion of proinflammatory cytokines, all of which suggest that these cells may play a role in the development of the autoimmune response in MS.

Tracing functional antigen-specific CCR6 Th17 cells after vaccination

Background

The function of T helper cell subsets in vivo depends on their location, and one hallmark of T cell differentiation is the sequential regulation of migration-inducing chemokine receptor expression. CC-chemokine receptor 6 (CCR6) is a trait of tissue-homing effector T cells and has recently been described as a receptor on T helper type 17 (Th17) cells. Th17 cells are associated with autoimmunity and the defence against certain infections. Although, the polarization of Th cells into Th17 cells has been studied extensively in vitro, the development of those cells during the physiological immune response is still elusive.

Methodology/Principal Findings

We analysed the development and functionality of Th17 cells in immune-competent mice during an ongoing immune response. In naïve and vaccinated animals CCR6⁺ Th cells produce IL-17. The robust homeostatic proliferation and the presence of activation markers on CCR6⁺ Th cells indicate their activated status. Vaccination induces antigen-specific CCR6⁺ Th17 cells that respond to in vitro re-stimulation with cytokine production and proliferation. Furthermore, depletion of CCR6⁺ Th cells from donor leukocytes prevents recipients from severe disease in experimental autoimmune encephalomyelitis, a model for multiple sclerosis in mice.

Conclusions/Significance

In conclusion, we defined CCR6 as a specific marker for functional antigen-specific Th17 cells during the immune response. Since IL-17 production reaches the highest levels during the immediate early phase of the immune response and the activation of Th17 cells precedes the Th1 cell differentiation we tent to speculate that this particular Th cell subset may represent a first line effector Th cell subpopulation. Interference with the activation of this Th cell subtype provides an interesting strategy to prevent autoimmunity as well as to establish protective immunity against infections.

Degenerate TCR recognition and dual DR2 restriction of autoreactive T cells: implications for the initiation of the autoimmune response in multiple sclerosis

TCR degeneracy may facilitate self-reactive T cell activation and the initiation of an autoimmune response in multiple sclerosis (MS). MHC class II alleles of the DR2 haplotype DR2a (DRB5*0101) and DR2b (DRB1*1501) are associated with an increased risk for MS in Caucasian populations. In order to selectively expand and characterize T cells with a high degree of TCR degeneracy that recognize peptides in the context of disease-associated DR2 alleles, we developed DR2-anchored peptide mixtures (APM). We report here that DR2-APM have a high stimulatory potency and can selectively expand T cells with a degenerate TCR (TCR(deg)). Due to the low concentration of individual peptides in the mixtures, T cell clones' proliferative response to DR2-APM implies that multiple peptides stimulate the TCR, which is a characteristic of TCR(deg). The frequency of DR2-APM-reactive T cells is significantly higher in MS patients than in healthy controls, suggesting that they may play a role in the development of the autoimmune response in MS. DR2-APM-reactive cells have a dual DR2 restriction: they recognize DR2-APM in the context of both DR2a and DR2b molecules. The DR2-APM-reactive cells' IL-17 secretion, together with cross-reactivity against myelin peptides, may contribute to their role in the development of autoimmune response in MS.

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. This review summarizes the relevance of polyspecificity for lymphocyte development, activation and disease processes.