scholarly journals Clonal deletion induced by either radioresistant thymic host cells or lymphohemopoietic donor cells at different stages of class I-restricted T cell ontogeny.

1992 ◽  
Vol 175 (5) ◽  
pp. 1277-1283 ◽  
Author(s):  
D E Speiser ◽  
H Pircher ◽  
P S Ohashi ◽  
D Kyburz ◽  
H Hengartner ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Positive Selection ◽  
Negative Selection ◽  
Host Cells ◽  
Thymic Epithelial Cells ◽  
Clonal Deletion ◽  
Mhc Molecules ◽  
Donor Cells ◽  
Self Antigens

Major histocompatibility complex (MHC) products and self-antigens expressed in the thymus determine the repertoire of mature alpha/beta T cells. While positive selection of self-MHC-restricted T cells is directed by MHC molecules expressed by thymic epithelial cells, negative selection depends to a large extent on self-antigens presented by lymphohemopoietic cells. However, radioresistant components of the thymus also influence negative selection, but it remains controversial whether this is accomplished by clonal deletion, clonal anergy, or other mechanisms. In this study, T cell development in mice expressing a transgenic T cell receptor (TCR) specific for lymphocytic choriomeningitis virus (LCMV) plus H-2Db was analyzed in the presence or absence of the viral antigen. A novel approach to analyze the thymic tissue requirements for negative selection was possible by comparing thymocyte selection in H-2Db versus H-2Dbm13 mice, since the latter allowed positive selection but not LCMV-specific deletion of transgenic TCR-expressing thymocytes. In irradiation bone marrow chimeras expressing the restriction element for negative selection (H-2Db) on host tissue, we show that radioresistant recipient cells in the thymus deleted developing T cells at an early stage of differentiation. In contrast, chimeras expressing H-2Db on lymphohemopoietic donor cells showed clonal deletion at a later stage during ontogeny.

Promoter IV of the class II transactivator gene is essential for positive selection of CD4+ T cells

Blood ◽  
2003 ◽  
Vol 101 (9) ◽  
pp. 3550-3559 ◽  
Author(s):  
Jean-Marc Waldburger ◽  
Simona Rossi ◽  
Georg A. Hollander ◽  
Hans-Reimer Rodewald ◽  
Walter Reith ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Epithelial Cells ◽  
Positive Selection ◽  
Negative Selection ◽  
Cd4 T Cell ◽  
Thymic Epithelial Cells ◽  
Mhcii Expression ◽  
Selection Of

Major histocompatibility complex class II (MHCII) expression is regulated by the transcriptional coactivator CIITA. Positive selection of CD4+ T cells is abrogated in mice lacking one of the promoters (pIV) of the Mhc2ta gene. This is entirely due to the absence of MHCII expression in thymic epithelia, as demonstrated by bone marrow transfer experiments between wild-type and pIV−/− mice. Medullary thymic epithelial cells (mTECs) are also MHCII− in pIV−/− mice. Bone marrow–derived, professional antigen-presenting cells (APCs) retain normal MHCII expression in pIV−/− mice, including those believed to mediate negative selection in the thymic medulla. Endogenous retroviruses thus retain their ability to sustain negative selection of the residual CD4+ thymocytes in pIV−/− mice. Interestingly, the passive acquisition of MHCII molecules by thymocytes is abrogated in pIV−/−mice. This identifies thymic epithelial cells as the source of this passive transfer. In peripheral lymphoid organs, the CD4+T-cell population of pIV−/− mice is quantitatively and qualitatively comparable to that of MHCII-deficient mice. It comprises a high proportion of CD1-restricted natural killer T cells, which results in a bias of the Vβ repertoire of the residual CD4+ T-cell population. We have also addressed the identity of the signal that sustains pIV expression in cortical epithelia. We found that the Jak/STAT pathways activated by the common γ chain (CD132) or common β chain (CDw131) cytokine receptors are not required for MHCII expression in thymic cortical epithelia.

scholarly journals P03.07 Analysis of scRNAseq from the human thymus nominates genes potentially missing from central tolerance of cytotoxic T cells

2021 ◽  
Vol 9 (Suppl 1) ◽  
pp. A15.2-A16
Author(s):  
L Blumenberg ◽  
G Atwal ◽  
A Dhanik
Keyword(s):  
T Cells ◽  
T Cell ◽  
Negative Selection ◽  
Cytotoxic T Cells ◽  
Peripheral Tolerance ◽  
Thymic Epithelial Cells ◽  
Central Tolerance ◽  
Human Thymus ◽  
Part Time ◽  
Self Antigens

BackgroundDuring thymic development, cytotoxic T cells that can bind to and attack self antigens undergo negative selection thus preventing damage to the self tissues. The sparse medullar thymic epithelial cells (mTECs) present in the thymus are responsible for presenting self antigens to T cells so that they can trigger apoptosis or differentiation into non-cytotoxic lineages if they bind too strongly.Materials and MethodsUnderstanding gene expression in mTECs is essential for understanding the shape of the human T cell receptor repertoire, which is key for current and emerging cancer immunotherapies. Recent availability of human thymus single cell RNAseq (scRNAseq) data provides an extremely high-resolution view into the pattern of expression within this critical cell type. To determine which epitopes have had to opportunity to be presented during T cell negative selection, we analyzed the human thymus scRNAseq dataset to establish which genes are expressed in mTECs and therefore subject to central tolerance.ResultsThe coverage of the whole transcriptome of a particular cell is generally sparse. It is therefore difficult to understand basic features of individual cells or cell types such as how many genes are expressed. We used cell- and read-level subsampling to estimate whether a sufficient number of cells and reads had been captured to support categorizing a gene as non-expressed in mTECs. We also examined the expression of the genes not expressed in mTECs in other healthy tissues, and found their expression was almost exclusively restricted to the testis (an immune-privileged site) and the liver (a site of peripheral tolerance)ConclusionsAltogether, these analyses establish a strategy for determining if a data set has sufficient depth to estimate the total number of genes expressed and secondly define a key list of genes that are not expressed during central tolerization of T cells, which represent a compelling list of possible cancer immunotherapy targets.Disclosure InformationL. Blumenberg: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals. G. Atwal: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals. A. Dhanik: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals.

scholarly journals Quantitative Impact of Thymic Clonal Deletion on the T Cell Repertoire

1997 ◽  
Vol 185 (3) ◽  
pp. 377-384 ◽  
Author(s):  
Joost P.M. van Meerwijk ◽  
Samuel Marguerat ◽  
Rosemary K. Lees ◽  
Ronald N. Germain ◽  
B.J. Fowlkes ◽  
...  
Keyword(s):  
Positive Selection ◽  
Negative Selection ◽  
De Novo ◽  
Thymic Epithelial Cells ◽  
Cell Repertoire ◽  
Clonal Deletion ◽  
Mhc Molecules ◽  
Specific Receptors ◽  
Bone Marrow Chimeras ◽  
Quantitative Impact

Interactions between major histocompatibility complex (MHC) molecules expressed on stromal cells and antigen-specific receptors on T cells shape the repertoire of mature T lymphocytes emerging from the thymus. Some thymocytes with appropriate receptors are stimulated to undergo differentiation to the fully mature state (positive selection), whereas others with strongly autoreactive receptors are triggered to undergo programmed cell death before completing this differentiation process (negative selection). The quantitative impact of negative selection on the potentially available repertoire is currently unknown. To address this issue, we have constructed radiation bone marrow chimeras in which MHC molecules are present on radioresistant thymic epithelial cells (to allow positive selection) but absent from radiosensitive hematopoietic elements responsible for negative selection. In such chimeras, the number of mature thymocytes was increased by twofold as compared with appropriate control chimeras. This increase in steady-state numbers of mature thymocytes was not related to proliferation, increased retention, or recirculation and was accompanied by a similar two- to threefold increase in the de novo rate of generation of mature cells. Taken together, our data indicate that half to two-thirds of the thymocytes able to undergo positive selection die before full maturation due to negative selection.

scholarly journals Cathepsin L Regulates CD4+ T Cell Selection Independently of Its Effect on Invariant Chain

2002 ◽  
Vol 195 (10) ◽  
pp. 1349-1358 ◽  
Author(s):  
Karen Honey ◽  
Terry Nakagawa ◽  
Christoph Peters ◽  
Alexander Rudensky
Keyword(s):  
T Cells ◽  
T Cell ◽  
Epithelial Cells ◽  
Positive Selection ◽  
Cathepsin L ◽  
Cd4 T Cell ◽  
Thymic Epithelial Cells ◽  
Invariant Chain ◽  
Cell Selection ◽  
T Cell Selection

CD4+ T cells are positively selected in the thymus on peptides presented in the context of major histocompatibility complex class II molecules expressed on cortical thymic epithelial cells. Molecules regulating this peptide presentation play a role in determining the outcome of positive selection. Cathepsin L mediates invariant chain processing in cortical thymic epithelial cells, and animals of the I-Ab haplotype deficient in this enzyme exhibit impaired CD4+ T cell selection. To determine whether the selection defect is due solely to the block in invariant chain cleavage we analyzed cathepsin L–deficient mice expressing the I-Aq haplotype which has little dependence upon invariant chain processing for peptide presentation. Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation. This was confirmed by analysis of I-Ab mice deficient in both cathepsin L and invariant chain. We show that the defect in positive selection in the cathepsin L−/− thymus is specific for CD4+ T cells that can be selected in a wild-type and provide evidence that the repertoire of T cells selected differs from that in wild-type mice, suggesting cortical thymic epithelial cells in cathepsin L knockout mice express an altered peptide repertoire. Thus, we propose a novel role for cathepsin L in regulating positive selection by generating the major histocompatibility complex class II bound peptide ligands presented by cortical thymic epithelial cells.

scholarly journals In vivo and in vitro clonal deletion of double-positive thymocytes.

1992 ◽  
Vol 175 (5) ◽  
pp. 1307-1316 ◽  
Author(s):  
N J Vasquez ◽  
J Kaye ◽  
S M Hedrick
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cytochrome C ◽  
Cyclosporin A ◽  
Negative Selection ◽  
Double Positive ◽  
Antigen Dose ◽  
Mhc Molecules

To study the processes of thymic development, we have established transgenic mice expressing and alpha/beta T cell antigen receptor (TCR) specific for cytochrome c associated with class II major histocompatibility complex (MHC) molecules. The transgenic TCR chains are expressed by most of the thymocytes in these mice, and these cells have been shown to efficiently mature in association with Ek- and Ab-encoded class II MHC molecules. This report describes a characterization of the negative selection of these transgenic thymocytes in vivo that is associated with the expression of As molecules. Negative selection by As molecules appears to result in the deletion of a late stage of CD4/CD8 double-positive thymocytes in that there is a virtual absence of transgenic TCR bearing CD4 single-positive thymocytes. This phenotype is accompanied by the appearance of CD4/CD8 double-negative thymocytes and peripheral T cells that are functionally antigen reactive. The process of negative selection has also been investigated using an in vitro culture system. Upon presentation of cytochrome c by Eb-expressing nonthymic antigen-presenting cells, there occurs an antigen dose-dependent deletion of the majority of CD4/CD8 double-positive thymocytes. In contrast, presentation of Staphylococcal enterotoxin A by Eb in vitro results in minimal deletion of double-positive thymocytes. In addition, we use this in vitro model to examine the effects of cyclosporin A on negative selection. In contrast to its effects on mature T cells, and the findings of others in vivo, cyclosporin A does not inhibit antigen-induced deletion of double-positive thymocytes. Finally, a comparison of the antigen dose responses for thymocyte deletion and for peripheral T cell activation indicates that double-positive thymocyte recognition is more sensitive than mature T cells to antigen recognition.

scholarly journals Self-antigen presentation by mouse B cells results in regulatory T-cell induction rather than anergy or clonal deletion

Blood ◽  
2011 ◽  
Vol 118 (4) ◽  
pp. 984-991 ◽  
Author(s):  
Sara Morlacchi ◽  
Cristiana Soldani ◽  
Antonella Viola ◽  
Adelaida Sarukhan
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Antigen Expression ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Clonal Deletion ◽  
Thymic Epithelium ◽  
Self Antigen ◽  
Self Antigens

Abstract Multiple mechanisms operate to ensure T-cell tolerance toward self-antigens. Three main processes have been described: clonal deletion, anergy, and deviation to CD4+ regulatory T cells (Tregs) that suppress autoreactive T cells that have escaped the first 2 mechanisms. Although it is accepted that dendritic cells (DCs) and B cells contribute in maintaining T-cell tolerance to self-antigens, their relative contribution and the processes involved under physiologic conditions remain only partially characterized. In this study, we used different transgenic mouse models to obtain chimeras where a neo self-antigen is expressed by thymic epithelium and/or by DCs or B cells. We found that expression of cognate ligand in the thymus enhances antigen-specific FoxP3+ cells independently of whether the self-antigen is expressed on thymic epithelium or only on DCs, but not on B cells. On the contrary, self-antigen expression by B cells was very efficient in inducing FoxP3+ cells in the periphery, whereas self-antigen expression by DC led mainly to deletion and anergy of antigen-specific FoxP3− cells. The results presented in this study underline the role of B cells in Treg induction and may have important implications in clinical protocols aimed at the peripheral expansion of Tregs in patients.

scholarly journals Strong T cell tolerance in parent----F1 bone marrow chimeras prepared with supralethal irradiation. Evidence for clonal deletion and anergy.

1990 ◽  
Vol 171 (4) ◽  
pp. 1101-1121 ◽  
Author(s):  
E K Gao ◽  
D Lo ◽  
J Sprent
Keyword(s):  
T Cells ◽  
T Cell ◽  
Epithelial Cells ◽  
Tolerance Induction ◽  
Thymic Epithelial Cells ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Cd4 Cells ◽  
Clonal Deletion ◽  
Host Type

T cell tolerance induction was examined in long-term H-2-heterozygous parent----F1 chimeras prepared with supralethal irradiation (1,300 rad). Although these chimeras appeared to be devoid of host-type APC, the donor T cells developing in the chimeras showed marked tolerance to host-type H-2 determinants. Tolerance to the host appeared to be virtually complete in four assay systems: (a) primary mixed lymphocyte reactions (MLR) of purified lymph node (LN) CD8+ cells (+/- IL-2); (b) primary MLR of CD4+ (CD8-) thymocytes; (c) skin graft rejection; and (d) induction of lethal graft-vs.-host disease by CD4+ cells. Similar tolerance was observed in chimeras given double irradiation. The only assay in which the chimera T cells failed to show near-total tolerance to the host was the primary MLR of post-thymic CD4+ cells. In this assay, LN CD4+ cells regularly gave a significant antihost MLR. The magnitude of this response was two- to fourfold less than the response of normal parental strain CD4+ cells and, in I-E(-)----I-E+ chimeras, was paralleled by approximately 70% deletion of V beta 11+ cells. Since marked tolerance was evident at the level of mature thymocytes, tolerance induction in the chimeras presumably occurred in the thymus itself. The failure to detect host APC in the thymus implies that tolerance reflected contact with thymic epithelial cells (and/or other non-BM-derived cells in the thymus). To account for the residual host reactivity of LN CD4+ cells and the incomplete deletion of V beta 11+ cells, it is suggested that T cell contact with thymic epithelial cells induced clonal deletion of most of the host-reactive T cells but spared a proportion of these cells (possibly low affinity cells). Since these latter cells appeared to be functionally inert in the thymus (in contrast to LN), we suggest that the thymic epithelial cells induced a temporary form of anergy in the remaining host-reactive thymocytes. This anergic state disappeared when the T cells left the thymus and reached LN.

scholarly journals Role of the H-2 complex in induction of T helper cells in vivo. I. Antigen-specific selection of donor T cells to sheep erythrocytes in irradiated mice dependent upon sharing of H-2 determinants between donor and host.

1978 ◽  
Vol 148 (2) ◽  
pp. 478-489 ◽  
Author(s):  
J Sprent
Keyword(s):  
T Cells ◽  
Positive Selection ◽  
T Helper Cells ◽  
Negative Selection ◽  
T Helper ◽  
F1 Hybrid ◽  
Sheep Erythrocytes ◽  
Helper Cells ◽  
Donor Cells ◽  
Helper Function

When purified CBA lymph node T cells were mixed with sheep erythrocytes (SRC) and filtered from blood to lymph through irradiated syngeneic mice for 1-2 days, the donor cells lost their capacity to stimulate anti-SRC responses by CBA B cells; the response to a third-party antigen (horse erythrocytes) was unaffected and active suppression was not involved. This process of specific negative selection to SRC also occurred when semiallogeneic mice were used as filtration hosts. By contrast, when allogeneic hosts were used the helper function of the donor cells was not reduced; this applied to both primed and unprimed T cells. Studied with congeneic resistant strains indicated that negative selection to SRC occurred only when the donor and host shared H-2 determinants. Studies with T cells depleted of alloreactive lymphocytes showed that negative selection to SRC in irradiated F1 hybrid mice was followed by a stage of positive selection where the donor cells gave greatly increased responses to the injected antigen. Positive selection did not occur in H-2-different mice, however, and the helper function of the donor cells remained unchanged. By these parameters it was concluded that homozygous T helper cells have no detectable capacity to recognize antigen in an H-2-different environment.

scholarly journals Proteasome-Generated cis-Spliced Peptides and Their Potential Role in CD8+ T Cell Tolerance

2021 ◽  
Vol 12 ◽  
Author(s):  
Artem Mansurkhodzhaev ◽  
Camila R. R. Barbosa ◽  
Michele Mishto ◽  
Juliane Liepe
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Response ◽  
Thymic Epithelial Cells ◽  
Antigenic Peptides ◽  
T Cell Tolerance ◽  
Cell Tolerance ◽  
Peptide Hydrolysis ◽  
Clonal Deletion ◽  
Infected Cells

The human immune system relies on the capability of CD8+ T cells to patrol body cells, spot infected cells and eliminate them. This cytotoxic response is supposed to be limited to infected cells to avoid killing of healthy cells. To enable this, CD8+ T cells have T Cell Receptors (TCRs) which should discriminate between self and non-self through the recognition of antigenic peptides bound to Human Leukocyte Antigen class I (HLA-I) complexes—i.e., HLA-I immunopeptidomes—of patrolled cells. The majority of these antigenic peptides are produced by proteasomes through either peptide hydrolysis or peptide splicing. Proteasome-generated cis-spliced peptides derive from a given antigen, are immunogenic and frequently presented by HLA-I complexes. Theoretically, they also have a very large sequence variability, which might impinge upon our model of self/non-self discrimination and central and peripheral CD8+ T cell tolerance. Indeed, a large variety of cis-spliced epitopes might enlarge the pool of viral-human zwitter epitopes, i.e., peptides that may be generated with the exact same sequence from both self (human) and non-self (viral) antigens. Antigenic viral-human zwitter peptides may be recognized by CD8+ thymocytes and T cells, induce clonal deletion or other tolerance processes, thereby restraining CD8+ T cell response against viruses. To test this hypothesis, we computed in silico the theoretical frequency of zwitter non-spliced and cis-spliced epitope candidates derived from human proteome (self) and from the proteomes of a large pool of viruses (non-self). We considered their binding affinity to the representative HLA-A*02:01 complex, self-antigen expression in Medullary Thymic Epithelial cells (mTECs) and the relative frequency of non-spliced and cis-spliced peptides in HLA-I immunopeptidomes. Based on the present knowledge of proteasome-catalyzed peptide splicing and neglecting CD8+ TCR degeneracy, our study suggests that, despite their frequency, the portion of the cis-spliced peptides we investigated could only marginally impinge upon the variety of functional CD8+ cytotoxic T cells (CTLs) involved in anti-viral response.

In Vivo T-Lymphocyte Tolerance in the Absence of Thymic Clonal Deletion Mediated by Hematopoietic Cells

Blood ◽  
1999 ◽  
Vol 93 (11) ◽  
pp. 3856-3862 ◽  
Author(s):  
Joost P.M. van Meerwijk ◽  
H. Robson MacDonald
Keyword(s):  
T Cells ◽  
T Cell ◽  
Negative Selection ◽  
Apoptotic Cell ◽  
Hematopoietic Cells ◽  
Cell Receptor ◽  
Cell Repertoire ◽  
Clonal Deletion

Abstract Thymic negative selection renders the developing T-cell repertoire tolerant to self-major histocompatability complex (MHC)/peptide ligands. The major mechanism of induction of self-tolerance is thought to be thymic clonal deletion, ie, the induction of apoptotic cell death in thymocytes expressing a self-reactive T-cell receptor. Consistent with this hypothesis, in mice deficient in thymic clonal deletion mediated by cells of hematopoietic origin, a twofold to threefold increased generation of mature thymocytes has been observed. Here we describe the analysis of the specificity of T lymphocytes developing in the absence of clonal deletion mediated by hematopoietic cells. In vitro, targets expressing syngeneic MHC were readily lysed by activated CD8+ T cells from deletion-deficient mice. However, proliferative responses of T cells from these mice on activation with syngeneic antigen presenting cells were rather poor. In vivo, deletion-deficient T cells were incapable of induction of lethal graft-versus-host disease in syngeneic hosts. These data indicate that in the absence of thymic deletion mediated by hematopoietic cells functional T-cell tolerance can be induced by nonhematopoietic cells in the thymus. Moreover, our results emphasize the redundancy in thymic negative selection mechanisms.

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