TCT.1, a target molecule for gamma/delta T cells, is encoded by an immunoglobulin superfamily gene (Blast-1) located in the CD1 region of human chromosome 1

Exploring T-cell exhaustion features in Acute myocardial infarction for a Novel Diagnostic model and new therapeutic targets by bio-informatics and machine learning

BACKGROUND

T-cell exhaustion (TEX), a condition characterized by impaired T-cell function, has been implicated in numerous pathological conditions, but its role in acute myocardial Infarction (AMI) remains largely unexplored. This research aims to identify and characterize all TEX-related genes for AMI diagnosis.

METHODS

By integrating gene expression profiles, differential expression analysis, gene set enrichment analysis, protein-protein interaction networks, and machine learning algorithms, we were able to decipher the molecular mechanisms underlying TEX and its significant association with AMI. In addition, we investigated the diagnostic validity of the leading TEX-related genes and their interactions with immune cell profiles. Different types of candidate small molecule compounds were ultimately matched with TEX-featured genes in the "DrugBank" database to serve as potential therapeutic medications for future TEX-AMI basic research.

RESULTS

We screened 1725 differentially expressed genes (DEGs) from 80 AMI samples and 71 control samples, identifying 39 differential TEX-related transcripts in total. Functional enrichment analysis identified potential biological functions and signaling pathways associated with the aforementioned genes. We constructed a TEX signature containing five hub genes with favorable prognostic performance using machine learning algorithms. In addition, the prognostic performance of the nomogram of these five hub genes was adequate (AUC between 0.815 and 0.995). Several dysregulated immune cells were also observed. Finally, six small molecule compounds which could be the future therapeutic for TEX in AMI were discovered.

CONCLUSION

Five TEX diagnostic feature genes, CD48, CD247, FCER1G, TNFAIP3, and FCGRA, were screened in AMI. Combining these genes may aid in the early diagnosis and risk prediction of AMI, as well as the evaluation of immune cell infiltration and the discovery of new therapeutics.

Human Vδ1+ T Cells in the Immune Response to Plasmodium falciparum Infection

Naturally acquired protective immunity to Plasmodium falciparum malaria is mainly antibody-mediated. However, other cells of the innate and adaptive immune system also play important roles. These include so-called unconventional T cells, which express a γδ T-cell receptor (TCR) rather than the αβ TCR expressed by the majority of T cells—the conventional T cells. The γδ T-cell compartment can be divided into distinct subsets. One expresses a TCR involving Vγ9 and Vδ2, while another major subset uses instead a TCR composed of Vδ1 paired with one of several types of γ chains. The former of these subsets uses a largely semi-invariant TCR repertoire and responds in an innate-like fashion to pyrophosphate antigens generated by various stressed host cells and infectious pathogens, including P. falciparum. In this short review, we focus instead on the Vδ1 subset, which appears to have a more adaptive immunobiology, but which has been much less studied in general and in malaria in particular. We discuss the evidence that Vδ1⁺ cells do indeed play a role in malaria and speculate on the function and specificity of this cell type, which is increasingly attracting the attention of immunologists.

T cell recognition of non-peptidic antigens in infectious diseases

The immune system has evolved to recognize a wide range of antigenic molecules of self and non-self origin. The stimulatory antigens form complexes with antigen-presenting molecules and directly interact with the T cell receptor (TCR). Peptidic antigens associate with major histocompatibility complex (MHC) molecules and therefore, are indicated as MHC-restricted. Non-peptidic antigens do not bind to MHC molecules and are presented by other classes of antigen-presenting molecules. These non-MHC restricted antigens include glycolipid molecules, phosphorylated metabolites of the mevalonate pathway and vitamin B2 precursors. T cells specific for non-peptidic antigens have important roles in host defense against infections, autoimmunity, allergies and tumour immunosurveillance. Hence, understanding the molecular interactions between the antigen presenting cell (APC) and the T cells with non-peptidic specificity is of great relevance. Here, we review current knowledge of this type of T cells, their TCR repertoire, the structural aspects of recognized antigens, the mode of antigen recognition, and their function with special emphasis on their role in infectious diseases.

The co-expression of 2B4 (CD244) and CD160 delineates a subpopulation of human CD8+ T cells with a potent CD160-mediated cytolytic effector function

Within human CD8+ T lymphocytes, the CD27-CD45RAhigh or CD56+ phenotypes contribute to precisely define the cells with CTL effector function. Novel markers were demonstrated to correlate with CTL properties, such as the 2B4 (CD244) receptor, a member of the CD2 subset of the immunoglobulin superfamily or the glycosylphosphatidylinositol-anchored CD160 receptor. We performed a study of these markers to further define the population of effectors with CTL functions. Here we show that cytotoxic subpopulations defined by surface markers CD160, CD56 and CD57 are mostly contained in the 2B4+CD8+ T cell population. Expression of CD160 identifies two populations in the 2B4+ population. The 2B4+CD160+ subset expresses a bona fide CTL phenotype. The co-expression of 2B4 and CD160 defines T cells containing high amounts of perforin and granzyme B. During CTL ontogeny, an up-regulation of 2B4 and CD160 is observed from a naive to a terminally differentiated phenotype. Finally, we demonstrated that CD160 triggering failed to induce cytotoxicity per se, but costimulated CD3-redirected killing. We conclude that the co-expression of 2B4 and CD160 defines a CD8+ T lymphocyte subpopulation with high CTL activity.

Natural killer cell-triggering receptors in patients with acute leukaemia

Human natural killer (NK) cells are potent effectors involved in destruction of virus infected cells and tumours. Their cytolytic function is regulated by surface receptors that either inhibit or increase the NK-mediated cytotoxicity. Under physiological conditions, NK cells recognize major histocompatibility complex (MHC)-class I molecules through surface receptors delivering signals that inhibit NK cells function. Nonetheless, the "missing self hypothesis", i.e. the release of an inhibitory signal by the interaction between HLA I-specific inhibitory receptors and their ligands, is not sufficient to entirely explain the regulation of NK cytotoxicity. Activating and co-receptors also play a central role in NK cell activation. In the haematology field, several lines of evidence suggest that NKs participate to the anti-leukaemia immune response: (1) leukaemic cells have down-regulated HLA-class I molecule expression and putative allele loss, (2) several reports have indicated an inverse relationship between NK cell number or activity and prognosis in acute leukaemia, (3) NK-cell activity dependent immunodeficiency syndromes are associated with an increased frequency of lymphoid haematological malignancies, (4) recent data support a role for NK cells in the graft-versus-leukaemia effect observed in allogeneic bone marrow transplantation. All these data raise several questions. How NK cells kill leukaemic targets, and how can leukaemia escape from innate immunity surveillance? What are the therapeutic possibilities to manipulate NK receptor-ligand interaction in order to increase leukaemia cell destruction? The responses to these questions will contribute to immunotherapy advancements in leukaemia and more generally in cancer.

Human gammadelta-T cells in adoptive immunotherapy of malignant and infectious diseases

Human gammadelta-T cells are capable of mediating both innate antitumor and antiviral activity, functions that theoretically might be exploitable in the treatment of a variety of malignant or infectious diseases. Nonetheless, experimental therapies incorporating the adoptive transter of human gammadelta-T cells have remained unfeasible to date owing largely to the difficulty of isolating or expanding sufficient numbers of gammadelta-T cells. It is in this context that recent discoveries from our laboratory are presented. By identifying specific signaling pathways that selectively inhibit activation-induced apoptosis in apoptosis-prone gammadelta-T cells, we have been able to expand large numbers of viable and functional human gammadelta-T cells, an undertaking until now notpossible. As important, these apoptosis-resistant gammadelta-Tcells appear to retain major histocompatibility complex-unrestricted (innate) antitumor activity against a wide variety of human tumor cells both in vitro and in vivo. Moreover, apoptosis-resistant gammadelta-T cells also display potent innate antiviral activity in vitro against human immunodeficiency virus-1. Both the biologic and practical implications of these findings are considered and discussed particularly as they relate to the development of future adoptive immunotherapy strategies.

A novel mechanism of antitumor response involving the expansion of CD3+/CD56+ large granular lymphocytes triggered by a tumor-expressed activating ligand

We describe a patient with acute myeloid leukemia (AML) who developed polyclonal large granular lymphocyte (LGL) proliferation. The reciprocal evolution of AML and LGLs suggested that these LGLs had an anti-tumor activity. The patient's LGLs killed autologous leukemia cells in a different way to classical T lymphocyte-mediated cytotoxicity since it did not rely on the recognition of target antigens presented by major histocompatibility complex (MHC) class I molecules by the CD3/TcRalphabeta complex. This killing was also different from natural killer (NK)-mediated cytotoxicity, which depends on the absence of MHC class I molecule recognition by NK inhibitory receptors. The LGLs were polyclonal, had a CD3+/CD8+/CD56+ phenotype, and did not express the natural killer cell receptors (NKRs) for MHC class I molecules. The LGLs did not express the NK-specific activating natural cytotoxicity receptors but expressed the 2B4 non-MHC restricted triggering receptor, whose ligand CD48 was expressed by leukemic cells and normal bone marrow cells. The 2B4 receptor participated in the ability of LGLs to lyse patient's leukemia. This represents a novel function for 2B4 in man, since this molecule, at variance with the murine system, was considered not to have direct effects on CD8+ T cell-mediated cytotoxicity. This case report allowed us to describe a novel T lymphocyte-mediated anti-tumor mechanism which relied on (1) the abnormal expansion of the rare 2B4-positive CD3+/CD8+/CD56+ T lymphocyte subset, (2) an as yet undescribed cytotoxicity mechanism in man which depended on 2B4 molecule. The relevance of this observation in human cancer immunotherapy has to be further investigated.

High frequency of circulating gamma delta T cells with dominance of the v(delta)1 subset in a healthy population

TCR gamma delta(+) cells constitute <5% of all circulating T cells in healthy, adult Caucasians, and V(delta)1(+) cells constitute a minority of these cells. In contrast to TCR alpha beta(+) cells, their repertoire is selected extrathymically by environmental antigens. Although increased frequencies of V(delta)1(+) cells are found in several diseases, their function remains obscure. Here we show that the frequency of peripheral blood gamma delta T cells in healthy West Africans is about twice that of Caucasians, mainly due to a 5-fold increase in V(delta)1(+) cells, which is consequently the dominant subset. No age dependency of V(delta)1 frequencies was identified and the V(delta)1(+) cells in the African donors did not show preferential V(gamma) chain usage. Analysis of the CDR3 region size did not reveal any particular skewing of the V(delta)1 repertoire, although oligoclonality was more pronounced in adults compared to children. The proportions of CD8(+), CD38(+) and CD45RA(hi)CD45RO(-) cells within the V(delta)1(+) subset were higher in the African than in the European donors, without obvious differences in expression of activation markers. No significant correlations between levels of V(delta)1(+) cells and environmental antigens or immunological parameters were identified. Taken together, the evidence argues against a CDR3-restricted, antigen-driven expansion of V(delta)1(+) cells in the African study population. Our study shows that high frequencies of TCR gamma delta(+) cells with dominance of the V(delta)1(+) subset can occur at the population level in healthy people, raising questions about the physiological role of V(delta)1(+) T cells in the function and regulation of the immune system.

Molecular cloning and biological characterization of NK cell activation-inducing ligand, a counterstructure for CD48

Using the monoclonal antibody C1.7, which recognizes a signaling, membrane-bound molecule on human NK and a proportion of CD8(+) T cells, we cloned a novel molecule we refer to as NK cell activation-inducing ligand (NAIL). It is a 365-amino acid protein that belongs to the immunoglobulin-like superfamily with closest homology to murine 2B4, and human CD84 and CD48. Using a soluble NAIL-Fc fusion protein, we determined the counterstructure for NAIL, CD48, which it binds with high affinity. Stimulation of human B cells with recombinant NAIL in the presence of a suboptimal concentration of human CD40 ligand or IL-4 resulted in increased proliferation. Treatment of human dendritic cells with soluble NAIL-leucine zipper protein resulted in an increased release of IL-12 and TNF-alpha. Using recombinant CD48 protein, we demonstrated the ability of this molecule to increase NK cell cytotoxicity and induce IFN-gamma production. We also showed that 2B4 binds to mouse CD48, suggesting that interaction of these receptors may play a similar role in both species. Taken together these results indicate that the NAIL-CD48 interaction may be an important mechanism regulating a variety of immune responses.

TCRgammadelta cells and viruses

T-cell receptor gammadelta cells (TCRgammadelta) are often found in increased numbers during the course of several viral infections in humans. Although these findings suggest an important role for this unique subset, their precise function has not been ascertained. Recent studies in murine models of both RNA and DNA virus infections have begun to shed new light on the potential function for TCRgammadelta cells in antiviral immunity. It is clear that TCRgammadelta cells participate in the immune response to human immunodeficiency virus (HIV), influenza, Sendai, coxsackie, vaccinia, vesicular stomatitis virus (VSV), and herpes simplex virus-1 (HSV-1) viral infections since they become activated and home to the sites of viral replication. In this review we will summarize current efforts to dissect the role of TCRgammadelta cells in these disease settings, emphasizing the effector functions utilized, the TCR repertoire, and the antigens recognized. Particular focus will be placed on HSV-1 infections where we have begun to address these issues and have shown that TCRgammadelta cells are sufficient for protection from lethal infection and are able to recognize the herpes virus antigen glycoprotein I.

HSV-1 Glycoprotein I-Reactive TCRγδ Cells Directly Recognize the Peptide Backbone in a Conformationally Dependent Manner

Despite the description of numerous antigenic ligands recognized by TCRγδ cells, detailed information concerning the structural nature of these antigenic epitopes is lacking. In addition, the recent descriptions of human TCRγδ cells recognizing mycobacterium-derived low m.w. lipid molecules confirms that the spectrum and nature of biologic structures that are capable of being recognized by TCRγδ cells are unclear. We have previously described a murine TCRγδ cell clone, TgI4.4, that is reactive to herpes simplex virus (HSV)-1 glycoprotein I (gI). Unlike TCRαβ-mediated, MHC-restricted Ag recognition but similar to Ig Ag recognition, TgI4.4 recognizes purified gI directly, in the absence of Ag processing or presentation. Since gI is a complex glycoprotein, the nature of the antigenic epitope was investigated. First, gI recognition by TgI4.4 is conformationally dependent, as revealed by denaturation and proteolytic experiments. Secondly, the epitope recognized by TgI4.4 was mapped to the amino terminus by using insertion mutants of gI. Lastly, TgI4.4 recognizes the gI protein directly since completely deglycosylated forms of gI are efficiently recognized. Therefore, TCRγδ cells are capable of recognizing a variety of molecular structures, including proteins. The ability of TgI4.4 to recognize a nonglycosylated form of gI suggests that HSV-1 recognition by TCRγδ cells in vivo is not limited by cell-specific glycosylation patterns or glycosylation-dependent conformational influences.

CD48 may serve as an accessory molecule for the activation of a subset of human gamma/delta T cells

To further assess the role of CD48 in the interaction of human gamma/delta T cells with their specific target, we generated two series of alloreactive clones, L and K. These clones express a V1-D-J1-C delta chain associated to V3-J2-C2 (L) or V2-J2-C2 (K) gamma chain. Functionally they were CTLs able to lyse the sensitizing B-cell line E418. The cytotoxicity of the L and K clones toward E418 was inhibited by anti-CD48 mAb. That of the L clones was also inhibited by anti-HLA class I mAbs. Variation in L and K lysis profile was observed against a panel of CD48+ targets, further strengthening the argument that they display distinct specificities and suggesting that they do not recognize CD48. Heterogeneity in TCR gene segment usage, MHC-dependent recognition of E418 by the L clones, and resistance of some CD48+ targets strongly suggest that CD48 itself does not interact with L and K TCR. Transfection of CHO cells with CD48 induced killing by the K clones. This killing was inhibited by anti-CD48 mAbs. Taking into account the recent reports on CD48 as an accessory molecule, our results suggest that by binding to CD2 (and/or an unknown ligand), CD48 may serve to strengthen E/T interaction and may contribute to the activation of a minor subset of gamma/delta T cells.

Human V gamma 9-V delta 2 cells are stimulated in a cross-reactive fashion by a variety of phosphorylated metabolites

Many different pathogens stimulate cells bearing the V gamma 9-V delta 2 T cell receptor (TCR), which represent the most abundant population of human gamma delta cells. The antigens responsible for the stimulation of these gamma delta cells are not well characterized. Here, we describe six non-peptidic molecules which share this property: isopentenylpyrophosphate, dimethylallylpyrophosphate, 2,3-diphosphoglyceric acid, glycerol-3-phosphoric acid, xylose-1-phosphate, and ribose-1-phosphate. All these molecules are naturally occurring metabolites in prokaryotic and eukaryotic cells, and stimulate freshly isolated gamma delta cells from peripheral blood of different donors as well as established gamma delta clones. Comparison of their structure with that of similar but inactive molecules showed that both the number and position of the phosphate groups, as well as the residues connected with the carbon backbone are required for stimulation. The CD3-TCR complex is involved in cell triggering as shown by inhibition with anti-CD3 Fab fragments. However, all gamma delta clones were broadly cross-reactive and we could not isolate cells specific for only one ligand. The capacity of this frequent subset of gamma delta cells to recognize common bacterial metabolites confers the advantage to react rapidly to different invading pathogens.

Human high-affinity Fc gamma RI (CD64) gene mapped to chromosome 1q21.2-q21.3 by fluorescence in situ hybridization

The human Fc gamma RI gene encodes for a high-affinity Fc gamma receptor that plays pivotal roles in the immune response. We have used fluorescence in situ hybridization analysis to localize the Fc gamma RI gene to human chromosome 1. The human Fc gamma RI (CD64) gene has been assigned to human chromosome 1q21.2-q21.3 using R-banded human (pro)metaphase chromosomes.

Multifunctional roles of glycosyl-phosphatidylinositol lipids

The results presented here indicate that GPI lipids are a structurally and functionally diverse molecular family. Despite new detailed information on the structures of GPI-anchored proteins, there is relatively scant information on the structure of free-GPI. Thus, little is known of the relationships between GPI structures and the mechanism of their biological effects. For example, there is no distinction at the structural level between hormone-sensitive free-GPI and those that serve as precursors for protein-GPI. Nor is there precise biochemical data on the mechanism and importance of free-GPI in hormone signaling, or the signaling roles that GPI anchors play in protein function. The T-cell activation cascade is an ideal system for studying both forms of GPI and their derivatives. The study of GPI molecules in T lymphocytes offers the exciting possibility of addressing questions on the structure, function, genesis, and regulation of both free- and protein-GPI molecules in a single cell type. The detection of multiple protein-GPI and free-GPI forms, and of hormone-sensitive GPI, provides the first approach to these issues. For the moment, the potential for biochemical signaling by intact GPI or its metabolites is enormous. If significant progress is to be made, the structures of hormone sensitive free-GPI must be elucidated. Only then can we precisely define the roles of these molecules in the regulation of cell metabolism and proliferation.

A subset of V delta 1+ T cells proliferates in response to Epstein-Barr virus-transformed B cell lines in vitro

It has previously been shown that murine tissue derived T-cells expressing the gamma delta T-cell receptor can respond to autologous (stressed) cells implying the recognition of an autoantigen. Here we report that a large proportion of human synovial tissue and peripheral blood derived V delta 1+ gamma delta T-cell clones proliferate in response to stimulation with autologous and allogeneic EBV-transformed B-lymphoblastoid cell lines (LCL). In contrast, V delta 1- gamma/delta and alpha/beta TCR+ T-cell clones isolated from the same tissue samples did not display proliferation towards the LCL. The proliferative response of these V delta 1+ clones was dependent on contact between responder and stimulator cells and could be blocked by a MoAb to LFA-1 and by antibodies to the gamma delta TCR/CD3 complex. Because the responses of these clones to LCL cells appear to be independent of the gamma-chain co-expressed with the V delta 1-chain these resemble a superantigen response. The capacity of this subset of V delta 1+ T-cell clones to proliferate after stimulation with LCL may imply the recognition of an endogenous epitope. Moreover, since so far we have been able to isolate only LCL reactive gamma delta T-cell clones from synovial tissue and peripheral blood of reactive arthritis patients and not from peripheral blood of healthy individuals, the frequency of such 'autoreactive' gamma delta cells may be higher in these patients.

T cell receptor junctional regions of V gamma 9+/V delta 2+ T cell clones in relation to non-MHC restricted cytotoxic activity

Human gamma delta T cell clones having V gamma 9JP and V delta 2DJ1 T cell receptor (TCR) gene rearrangements were isolated form an individual donor and tested for non-MHC restricted cytotoxicity against the B lymphoblastoid cell line, BSM. Most clones were highly cytotoxic but 3/9 clones had very low activity, comparable to that of CD4+ alpha beta T cell clones. Although there was a tendency for clones with low cytotoxic function to produce high levels of interferon-gamma and tumor necrosis factor-alpha, this correlation was not complete. TCR gamma and delta junctional sequences were obtained and were found to be different for all clones. There were no consistent structural differences between gamma delta TCRs of cytotoxic and non-cytotoxic clones, but gamma or delta junctional regions of all three non-cytotoxic clones had unusual features. One clone had a particularly short gamma chain junctional sequence, one had a short delta chain junctional sequence and the third clone was the only one of the panel which failed to utilise the D delta 3 segment. If the gamma delta TCR is involved in target cell recognition in this model of non-MHC restricted killing, such variations in receptor structure may be sufficient to inhibit recognition and thereby reduce the cytotoxic capacity of a minority of V gamma 9+/V delta 2+ clones. Also, a panel of gamma delta T cell clones expressing V gamma 8/V delta 3 isolated from a different donor, were all highly cytotoxic against BSM, indicating that these target cells can be recognised by effector cells expressing a TCR other than the V gamma 9/V delta 2 receptor. The possible influence of other cell surface molecules on non-MHC restricted cytotoxic function is discussed.

Preferential V delta 1 expression among TcR gamma/delta-bearing T cells in human oral epithelium

The oral cavity is a septic area colonized by various bacterial species, and the oral mucosa is frequently submitted to microtraumas. Several mechanisms are implicated in the defence of the oral tissue, but little is known concerning the eventual presence and role of gamma/delta T cells at this site. Samples of healthy keratinized oral mucosa were examined with immunochemical techniques using anti-CD3, CD4, CD8, CD22, TcR delta 1, V delta 1 and V delta 2 monoclonal antibodies. Whatever the site examined, gamma/delta T cells represent at most 2% of the T-cell population, a value similar to that found in other tissues. In the connective tissue, under the basement membrane, V delta 2+ gamma/delta T cells are predominant whereas the epithelium mostly contains V delta 1+ gamma/delta T cells. The significance of this preferential V delta 1 intraepithelial presence is discussed.