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Modeling the Dynamics of T-Cell Development in the Thymus. ENTROPY 2021; 23:e23040437. [PMID: 33918050 PMCID: PMC8069328 DOI: 10.3390/e23040437] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/01/2021] [Accepted: 04/05/2021] [Indexed: 12/24/2022]
Abstract
The thymus hosts the development of a specific type of adaptive immune cells called T cells. T cells orchestrate the adaptive immune response through recognition of antigen by the highly variable T-cell receptor (TCR). T-cell development is a tightly coordinated process comprising lineage commitment, somatic recombination of Tcr gene loci and selection for functional, but non-self-reactive TCRs, all interspersed with massive proliferation and cell death. Thus, the thymus produces a pool of T cells throughout life capable of responding to virtually any exogenous attack while preserving the body through self-tolerance. The thymus has been of considerable interest to both immunologists and theoretical biologists due to its multi-scale quantitative properties, bridging molecular binding, population dynamics and polyclonal repertoire specificity. Here, we review experimental strategies aimed at revealing quantitative and dynamic properties of T-cell development and how they have been implemented in mathematical modeling strategies that were reported to help understand the flexible dynamics of the highly dividing and dying thymic cell populations. Furthermore, we summarize the current challenges to estimating in vivo cellular dynamics and to reaching a next-generation multi-scale picture of T-cell development.
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2
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Abstract
In this issue of Immunity, Chopp et. al. use single-cell transcriptomics and epigenomics in mice and human samples to delineate developmental trajectories of αβ T cell subsets and refine the kinetic selection model of CD4+ and CD8+ T cell lineage commitment.
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Affiliation(s)
- Sarah B Cleveland
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Eric S Huseby
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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3
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Effects of thymic selection on T cell recognition of foreign and tumor antigenic peptides. Proc Natl Acad Sci U S A 2017; 114:E7875-E7881. [PMID: 28874554 DOI: 10.1073/pnas.1708573114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The advent of cancer immunotherapy has generated renewed hope for the treatment of many malignancies by introducing a number of novel strategies that exploit various properties of the immune system. These therapies are based on the idea that cytotoxic T lymphocytes (CTLs) directly recognize and respond to tumor-associated neoantigens (TANs) in much the same way as they would to foreign peptides presented on cell surfaces. To date, however, nearly all attempts to optimize immunotherapeutic strategies have been empirical. Here, we develop a model of T cell selection based on the assumption of random interaction strengths between a self-peptide and the various T cell receptors. The model enables the analytical study of the effects of selection on the CTL recognition of TANs and completely foreign peptides and can estimate the number of CTLs that can detect donor-matched transplants. We show that negative selection thresholds chosen to reflect experimentally observed thymic survival rates result in near-optimal production of T cells that are capable of surviving selection and recognizing foreign antigen. These analytical results are confirmed by simulation.
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Reinherz EL, Wang JH. Codification of bidentate pMHC interaction with TCR and its co-receptor. Trends Immunol 2015; 36:300-6. [PMID: 25818864 PMCID: PMC4420642 DOI: 10.1016/j.it.2015.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 03/03/2015] [Accepted: 03/04/2015] [Indexed: 02/03/2023]
Abstract
A 1983 Immunology Today rostrum hypothesized that each T cell has two recognition units: a T cell receptor (TCR) complex, which binds antigen associated with a polymorphic region of a MHC molecule (pMHC), and a CD4 or CD8 molecule that binds to a conserved region of that same MHC gene product (class II or I, respectively). Structural biology has since precisely revealed those bidentate pMHC interactions. TCRαβ ligates the membrane-distal antigen-binding MHC platform, whereas CD8 clamps a membrane-proximal MHCI α3 domain loop and CD4 docks to a hydrophobic crevice between MHCII α2 and β2 domains. Here, we review how MHC class-restricted binding impacts signaling and lineage commitment, discussing TCR force-driven conformational transitions that may optimally expose the co-receptor docking site on MHC.
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Affiliation(s)
- Ellis L Reinherz
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
| | - Jia-huai Wang
- Laboratory of Immunobiology and Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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5
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Abstract
The peripheral T cell repertoire is sculpted from prototypic T cells in the thymus bearing randomly generated T cell receptors (TCR) and by a series of developmental and selection steps that remove cells that are unresponsive or overly reactive to self-peptide–MHC complexes. The challenge of understanding how the kinetics of T cell development and the statistics of the selection processes combine to provide a diverse but self-tolerant T cell repertoire has invited quantitative modeling approaches, which are reviewed here.
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Affiliation(s)
- Andrew J Yates
- Departments of Systems and Computational Biology, Microbiology and Immunology, Albert Einstein College of Medicine , New York, NY , USA
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6
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Li XL, Teng MK, Reinherz EL, Wang JH. Strict Major Histocompatibility Complex Molecule Class-Specific Binding by Co-Receptors Enforces MHC-Restricted αβ TCR Recognition during T Lineage Subset Commitment. Front Immunol 2013; 4:383. [PMID: 24319443 PMCID: PMC3837227 DOI: 10.3389/fimmu.2013.00383] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/04/2013] [Indexed: 01/22/2023] Open
Abstract
Since the discovery of co-receptor dependent αβTCR recognition, considerable effort has been spent on elucidating the basis of CD4 and CD8 lineage commitment in the thymus. The latter is responsible for generating mature CD4 helper and CD8αβ cytotoxic T cell subsets. Although CD4+ and CD8+ T cell recognition of peptide antigens is known to be MHC class II- and MHC class I-restricted, respectively, the mechanism of single positive (SP) thymocyte lineage commitment from bipotential double-positive (DP) progenitors is not fully elucidated. Classical models to explain thymic CD4 vs. CD8 fate determination have included a stochastic selection model or instructional models. The latter are based either on strength of signal or duration of signal impacting fate. More recently, differential co-receptor gene imprinting has been shown to be involved in expression of transcription factors impacting cytotoxic T cell development. Here, we address commitment from a structural perspective, focusing on the nature of co-receptor binding to MHC molecules. By surveying 58 MHC class II and 224 MHC class I crystal structures in the Protein Data Bank, it becomes clear that CD4 cannot bind to MHC I molecules, nor can CD8αβ or CD8αα bind to MHC II molecules. Given that the co-receptor delivers Lck to phosphorylate exposed CD3 ITAMs within a peptide/MHC (pMHC)-ligated TCR complex to initiate cell signaling, this strict co-receptor recognition fosters MHC class-restricted SP thymocyte lineage commitment at the DP stage even though both co-receptors are expressed on a single cell. In short, the binding preference of an αβTCR for a peptide complexed with an MHC molecule dictates which co-receptor subsequently binds, thereby supporting development of that subset lineage. How function within the lineage is linked further to biopotential fate determination is discussed.
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Affiliation(s)
- Xiao-Long Li
- School of Life Sciences, University of Science and Technology of China , Hefei , China ; College of Life Sciences, Peking University , Beijing , China
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7
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Sarafova SD, Van Laethem F, Adoro S, Guinter T, Sharrow SO, Feigenbaum L, Singer A. Upregulation of CD4 expression during MHC class II-specific positive selection is essential for error-free lineage choice. Immunity 2009; 31:480-90. [PMID: 19747858 DOI: 10.1016/j.immuni.2009.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 06/19/2009] [Accepted: 07/07/2009] [Indexed: 11/25/2022]
Abstract
The lineage fate of developing thymocytes is determined by the persistence or cessation of T cell receptor (TCR) signaling during positive selection, with persistent TCR signaling required for CD4 lineage choice. We show here that transcriptional upregulation of CD4 expression is essential for error-free lineage choice during major histocompatibility complex class II (MHC II)-specific positive selection and is critical for error-free lineage choice in TCR-transgenic mice whose thymocytes compete for the identical selecting ligand. CD4 upregulation occurred for endogenously encoded CD4 coreceptors, but CD4 transgenes were downregulated during positive selection, disrupting MHC II-specific TCR signaling and causing lineage errors regardless of the absolute number or signaling strength of transgenic CD4 proteins. Thus, the kinetics of CD4 coreceptor expression during MHC II-specific positive selection determines the integrity of CD4 lineage choice, revealing an elegant symmetry between coreceptor kinetics and lineage choice.
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Affiliation(s)
- Sophia D Sarafova
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD 20892, USA
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8
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Ladi E, Schwickert TA, Chtanova T, Chen Y, Herzmark P, Yin X, Aaron H, Chan SW, Lipp M, Roysam B, Robey EA. Thymocyte-dendritic cell interactions near sources of CCR7 ligands in the thymic cortex. THE JOURNAL OF IMMUNOLOGY 2008; 181:7014-23. [PMID: 18981121 DOI: 10.4049/jimmunol.181.10.7014] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Little is known about the dynamics of the interactions between thymocytes and other cell types, as well as the spatiotemporal distribution of thymocytes during positive selection in the microenvironment of the cortex. We used two-photon laser scanning microscopy of the mouse thymus to visualize thymocytes and dendritic cells (DCs) and to characterize their interactions in the cortex. We show that thymocytes make frequent contacts with DCs in the thymic cortex and that these associations increase when thymocytes express T cell receptors that mediate positive selection. We also show that cortical DCs and the chemokine CCL21 expression are closely associated with capillaries throughout the cortex. The overexpression of the chemokine receptor CCR7 in thymocytes results in an increase in DC-thymocyte interactions, while the loss of CCR7 in the background of a positive-selecting TCR reduces the extent of DC-thymocyte interactions. These observations identify a vasculature-associated microenvironment within the thymic cortex that promotes interactions between DCs and thymocytes that are receiving positive selection signals.
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Affiliation(s)
- Ena Ladi
- Division of Immunology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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9
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Singer A, Adoro S, Park JH. Lineage fate and intense debate: myths, models and mechanisms of CD4- versus CD8-lineage choice. Nat Rev Immunol 2008; 8:788-801. [PMID: 18802443 DOI: 10.1038/nri2416] [Citation(s) in RCA: 335] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Following successful gene rearrangement at alphabeta T-cell receptor (TCR) loci, developing thymocytes express both CD4 and CD8 co-receptors and undergo a life-or-death selection event, which is known as positive selection, to identify cells that express TCRs with potentially useful ligand specificities. Positively selected thymocytes must then differentiate into either CD4(+) helper T cells or CD8(+) cytotoxic T cells, a crucial decision known as CD4/CD8-lineage choice. In this Review, we summarize recent advances in our understanding of the cellular and molecular events involved in lineage-fate decision and discuss them in the context of the major models of CD4/CD8-lineage choice.
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Affiliation(s)
- Alfred Singer
- Experimental Immunology Branch, National Cancer Institute, Bethesda, Maryland 20892, USA.
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10
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Buonocore F, Randelli E, Casani D, Guerra L, Picchietti S, Costantini S, Facchiano AM, Zou J, Secombes CJ, Scapigliati G. A CD4 homologue in sea bass (Dicentrarchus labrax): molecular characterization and structural analysis. Mol Immunol 2008; 45:3168-77. [PMID: 18403019 DOI: 10.1016/j.molimm.2008.02.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 02/29/2008] [Indexed: 11/15/2022]
Abstract
CD4 is a transmembrane glycoprotein fundamental for cell-mediated immunity. Its action as a T cell co-receptor increases the avidity of association between a T cell and an antigen-presenting cell by interacting with portions of the complex between MHC class II and TR molecules. In this paper we report the cDNA cloning, expression and structural analysis of a CD4 homologue from sea bass (Dicentrarchus labrax). The sea bass CD4 cDNA consists of 2071 bp that translates in one reading frame to give the entire molecule containing 480 amino acids. The analysis of the sequence shows the presence of four putative Ig-like domains and that some fundamental structural features, like a disulphide bond in domain D2 and the CXC signalling motif in the cytoplasmic tail, are conserved from sea bass to mammals. Real-time PCR analysis showed that very high levels of CD4 mRNA transcripts are present in thymus, followed by gut and gills. In vitro stimulation of head kidney leukocytes with LPS and PHA-L gave an increase of CD4 mRNA levels after 4h and a decrease after 24h. Homology modelling has been applied to create a 3D model of sea bass CD4 and to investigate its interaction with sea bass MHC-II. The analysis of the 3D complex between sea bass CD4 and sea bass MHC-II suggests that the absence of a disulfide bond in the CD4 D1 domain could make this molecule more flexible, inducing a different conformation and affecting the binding and the way of interaction between CD4 and MHC-II. Our results will add new insights into the sea bass T cell immune responses and will help in the identification of T cell subsets in teleost fishes to better understand the evolution of cell-mediated immunity from fish to mammals.
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Affiliation(s)
- Francesco Buonocore
- Dipartimento di Scienze Ambientali, University of Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy.
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11
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Serwold T, Hochedlinger K, Inlay MA, Jaenisch R, Weissman IL. Early TCR expression and aberrant T cell development in mice with endogenous prerearranged T cell receptor genes. THE JOURNAL OF IMMUNOLOGY 2007; 179:928-38. [PMID: 17617584 DOI: 10.4049/jimmunol.179.2.928] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The factors that regulate the rate of production of T cells by the thymus remain incompletely defined. To test whether generation of functional T cell receptors limits the rate of thymic T cell export, we made use of a line of mice, LN3alphabeta, that have endogenously prerearranged TCR genes. The prerearranged TCR genes were expressed abnormally early in hemopoietic development, indicating that RAG-mediated recombination, rather than transcription factor expression, is the key determinant of the initiation of robust TCR transcription. Thymic T cell export rates were similar between wild-type (wt) and LN3alphabeta mice, indicating that T cell maturation rates in these mice are determined by factors other than TCR gene rearrangement. In competitive bone marrow chimeras, however, LN3alphabeta thymocytes were out-competed by wt cells and failed to develop beyond the double-negative 4 stage. Furthermore, wt progenitors transplanted intrathymically into LN3alphabeta mice proliferated excessively, suggesting that increased proliferative signals in the LN3alphabeta thymus compensate for faulty T cell development driven by early TCR expression.
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MESH Headings
- Animals
- Cell Differentiation/immunology
- Flow Cytometry
- Gene Rearrangement, T-Lymphocyte/genetics
- Gene Rearrangement, T-Lymphocyte/immunology
- Genes, RAG-1
- Mice
- Mice, Mutant Strains
- Nuclear Transfer Techniques
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/immunology
- Receptors, Antigen, T-Cell/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Thymus Gland/cytology
- Thymus Gland/growth & development
- Thymus Gland/immunology
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Affiliation(s)
- Thomas Serwold
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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12
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Abstract
TCRαβ signaling is crucial for the maturation of CD4 and CD8 T cells, but the role of the Notch signaling pathway in this process is poorly understood. Genes encoding Presenilin (PS) 1/2 were deleted to prevent activation of the multiple Notch receptors expressed by developing thymocytes. PS1/2 knockout thymocyte precursors inefficiently generate CD4 T cells, a phenotype that is most pronounced when thymocytes bear a single major histocompatibility complex (MHC) class II–restricted T cell receptor (TCR). Diminished T cell production correlated with evidence of impaired TCR signaling, and could be rescued by manipulations that enhance MHC recognition. Although Notch appears to directly regulate binary fate decisions in many systems, these findings suggest a model in which PS-dependent Notch signaling influences positive selection and the development of αβ T cells by modifying TCR signal transduction.
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Affiliation(s)
- Karen Laky
- Laboratory of Cellular and Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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13
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Erman B, Alag AS, Dahle O, van Laethem F, Sarafova SD, Guinter TI, Sharrow SO, Grinberg A, Love PE, Singer A. Coreceptor signal strength regulates positive selection but does not determine CD4/CD8 lineage choice in a physiologic in vivo model. THE JOURNAL OF IMMUNOLOGY 2007; 177:6613-25. [PMID: 17082573 DOI: 10.4049/jimmunol.177.10.6613] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TCR signals drive thymocyte development, but it remains controversial what impact, if any, the intensity of those signals have on T cell differentiation in the thymus. In this study, we assess the impact of CD8 coreceptor signal strength on positive selection and CD4/CD8 lineage choice using novel gene knockin mice in which the endogenous CD8alpha gene has been re-engineered to encode the stronger signaling cytoplasmic tail of CD4, with the re-engineered CD8alpha gene referred to as CD8.4. We found that stronger signaling CD8.4 coreceptors specifically improved the efficiency of CD8-dependent positive selection and quantitatively increased the number of MHC class I (MHC-I)-specific thymocytes signaled to differentiate into CD8+ T cells, even for thymocytes expressing a single, transgenic TCR. Importantly, however, stronger signaling CD8.4 coreceptors did not alter the CD8 lineage choice of any MHC-I-specific thymocytes, even MHC-I-specific thymocytes expressing the high-affinity F5 transgenic TCR. This study documents in a physiologic in vivo model that coreceptor signal strength alters TCR-signaling thresholds for positive selection and so is a major determinant of the CD4:CD8 ratio, but it does not influence CD4/CD8 lineage choice.
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MESH Headings
- Animals
- CD4 Antigens/biosynthesis
- CD4 Antigens/genetics
- CD4 Antigens/physiology
- CD4-Positive T-Lymphocytes/cytology
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/metabolism
- CD8 Antigens/biosynthesis
- CD8 Antigens/genetics
- CD8 Antigens/physiology
- CD8-Positive T-Lymphocytes/cytology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Cell Line
- Cell Lineage/genetics
- Cell Lineage/immunology
- Female
- Killer Cells, Natural/cytology
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Mice, Transgenic
- Models, Immunological
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Signal Transduction/genetics
- Signal Transduction/immunology
- T-Lymphocytes, Helper-Inducer/cytology
- T-Lymphocytes, Helper-Inducer/immunology
- T-Lymphocytes, Helper-Inducer/metabolism
- Up-Regulation/immunology
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Affiliation(s)
- Batu Erman
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD 20892, USA
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14
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Sarafova SD, Erman B, Yu Q, Van Laethem F, Guinter T, Sharrow SO, Feigenbaum L, Wildt KF, Ellmeier W, Singer A. Modulation of Coreceptor Transcription during Positive Selection Dictates Lineage Fate Independently of TCR/Coreceptor Specificity. Immunity 2005; 23:75-87. [PMID: 16039581 DOI: 10.1016/j.immuni.2005.05.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 05/13/2005] [Accepted: 05/19/2005] [Indexed: 11/24/2022]
Abstract
For developing T cells, coreceptor choice is matched to T cell antigen receptor (TCR) MHC specificity during positive selection in the thymus, but the mechanism remains uncertain. Here, we document that TCR-mediated positive selection signals inactivate the immature CD8(III) enhancer in double positive (DP) thymocytes, explaining in part the cessation of CD8 coreceptor transcription that occurs during positive selection. More importantly, by placing CD4 protein expression under the control of CD8 transcriptional regulatory elements, we demonstrate that cessation of CD4 coreceptor transcription during positive selection results in precisely the same lineage fate as cessation of CD8 coreceptor transcription. That is, MHC-II-signaled DP thymocytes differentiated into CD8-lineage cytotoxic T cells, despite the MHC-II specificity and CD4 dependence of their TCRs. This study demonstrates that termination of coreceptor transcription during positive selection promotes CD8-lineage fate, regardless of TCR specificity or coreceptor protein identity.
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Affiliation(s)
- Sophia D Sarafova
- Experimental Immunology Branch, National Cancer Institute, Bethesda, Maryland 20892, USA
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15
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Delaire S, Huang YH, Chan SW, Robey EA. Dynamic repositioning of CD4 and CD8 genes during T cell development. ACTA ACUST UNITED AC 2005; 200:1427-35. [PMID: 15583015 PMCID: PMC2211942 DOI: 10.1084/jem.20041041] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although stable repression of CD4 and CD8 genes is a central feature of T cell lineage commitment, we lack detailed information about the timing and mechanism of this repression. Stable gene repression has been linked to the position of genes within the nucleus. Therefore, information about the nuclear position of CD4 and CD8 genes during T cell development could provide insights into both the mechanism of regulation of CD4 and CD8 genes, and the process of lineage commitment. Here, we report that lineage-specific repression of CD4 and CD8 genes is associated with the repositioning of alleles close to heterochromatin. We also provide evidence that the relocalization of CD4 and CD8 genes to heterochromatin can occur as an early response to positive selection signals. We discuss our results in terms of our current knowledge of CD4 and CD8 gene regulation and CD4 versus CD8 lineage commitment.
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Affiliation(s)
- Stephanie Delaire
- Department of Molecular and Cell Biology, 475 Life Science Additions, University of California, Berkeley, Berkeley, CA 94720, USA
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16
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Krenger W, Schmidlin H, Cavadini G, Holländer GA. On the relevance of TCR rearrangement circles as molecular markers for thymic output during experimental graft-versus-host disease. THE JOURNAL OF IMMUNOLOGY 2004; 172:7359-67. [PMID: 15187112 DOI: 10.4049/jimmunol.172.12.7359] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Efficient reconstitution of the pool of peripheral T cells after hemopoietic stem cell transplantation (HSCT) is dependent on normal thymic function. However, the development of graft-vs-host disease (GVHD) in the context of allogeneic HSCT is associated with injurious effects on thymocyte development. In this study, we examined in models of syngeneic and allogeneic murine HSCT whether actual posttransplant thymic output is accurately reflected by analysis of signal-joint TCR rearrangement excision circles (sjTRECs). Our data demonstrate that the de novo generation of T cells following syngeneic HSCT of T cell-deficient B6.RAG2(-/-) (recombination-activating gene 2(-/-)) mice correlates firmly with an increase of sjTRECs in the thymus and spleen. However, the altered homeostasis of naive peripheral T cells in the presence of GVHD necessitates the combined analysis of cell division in vivo and determinations of sjTREC contents and total sjTREC numbers to draw informative conclusions. From our data, we substantiate that thymic output and peripheral division of newly generated T cells are diminished in the presence of acute GVHD in an experimental radiation/allogeneic HSCT model.
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Affiliation(s)
- Werner Krenger
- Pediatric Immunology, Departments of Research and Clinical-Biological Sciences, University of Basel, and University Children's Hospital of Basel, Kantonsspital, Hebelstrasse 20, CH-4031 Basel, Switzerland.
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17
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Singer A, Bosselut R. CD4/CD8 coreceptors in thymocyte development, selection, and lineage commitment: analysis of the CD4/CD8 lineage decision. Adv Immunol 2004; 83:91-131. [PMID: 15135629 DOI: 10.1016/s0065-2776(04)83003-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Alfred Singer
- Experimental Immunology Branch, National Cancer Institute, Bethesda, Maryland 20892, USA
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18
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McCarty N, Shinohara ML, Lu L, Cantor H. Detailed analysis of gene expression during development of T cell lineages in the thymus. Proc Natl Acad Sci U S A 2004; 101:9339-44. [PMID: 15190182 PMCID: PMC438978 DOI: 10.1073/pnas.0402654101] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The genetic mechanisms that promote lineage commitment and eliminate autoreactive cells in the thymus are not well understood. To better understand this process, we have identified and quantitated transcripts in the two major thymocyte lineages by using serial analysis of gene expression. Approximately 25 genes displayed almost complete segregation to one or the other T cell lineage. Commitment to the CD4 lineage was marked by up-regulation of genes associated with increased survival and chaperone function followed by expression of genes that regulate nucleosome remodeling and T cell receptor signaling. Differentiation within the CD8 lineage, on the other hand, was marked by up-regulation of genes that regulate lymphocyte homing, followed by quenching of genes that inhibit apoptosis. Definition of differential gene expression during development of the two major thymocyte lineages will allow insight into mechanisms of T cell development after positive and negative selection.
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Affiliation(s)
- Nami McCarty
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, and Department of Pathology, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA
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19
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Huang YH, Li D, Winoto A, Robey EA. Distinct transcriptional programs in thymocytes responding to T cell receptor, Notch, and positive selection signals. Proc Natl Acad Sci U S A 2004; 101:4936-41. [PMID: 15044701 PMCID: PMC387352 DOI: 10.1073/pnas.0401133101] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
T cell antigen receptor (TCR) signaling is necessary but not sufficient to promote the positive selection of CD4+CD8+ thymocytes into CD4+ or CD8+ mature T cells. Notch signaling has also been implicated as a potential regulator of both CD4/CD8 T cell development and TCR signaling. However, the relationship between positive selection, TCR signaling, and Notch remains unclear. Here we use DNA microarray analysis to compare gene expression changes in CD4+CD8+ double-positive thymocytes undergoing positive selection, TCR stimulation, and Notch activation. We find that the genes induced during positive selection can be resolved into two distinct sets. One set, which we term "TCR-induced," is also induced by in vitro TCR stimulation and contains a large proportion of transcription factors. A second set, which we term "positive-selection-induced," is not induced by in vitro TCR simulation and contains a large proportion of genes involved in signal transduction pathways. Genes induced by Notch activity overlap substantially with genes induced during positive selection. We also find that Notch activity potentiates the effects of TCR stimulation on gene expression. These results help to identify TCR- and positive-selection-specific transcriptional events and help to clarify the relationship between positive selection and Notch.
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Affiliation(s)
- Yina H Huang
- Department of Molecular and Cell Biology, Division of Immunology and Cancer Research Laboratory, 475 LSA, University of California, Berkeley, CA 94720, USA
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20
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Canelles M, Park ML, Schwartz OM, Fowlkes BJ. The influence of the thymic environment on the CD4-versus-CD8 T lineage decision. Nat Immunol 2003; 4:756-64. [PMID: 12858172 DOI: 10.1038/ni953] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2003] [Accepted: 06/13/2003] [Indexed: 01/22/2023]
Abstract
T cell receptor signaling is an essential factor regulating thymocyte selection, but the function of the thymic environment in this process is not clear. In mice transgenic for major histocompatibility complex class II-restricted T cell receptors, every thymocyte is potentially selectable for maturation in the CD4 lineage. To address whether selection frequency affects positive selection, we created hematopoietic chimeras with mixtures of selectable and nonselectable precursors. With increased proportions of nonselectable thymocytes, positive selection of MHC class II-specific precursors was enhanced, generating not only CD4 but also CD8 thymocytes. These results indicate that the CD4 versus CD8 fate of selectable precursors can be influenced by the selection potential of its neighbors.
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Affiliation(s)
- Matilde Canelles
- Laboratory of Cellular and Molecular Immunology, Building 4, Room 111, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0420, USA
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21
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Abstract
Cell-fate decisions are controlled typically by conserved receptors that interact with co-evolved ligands. Therefore, the lineage-specific differentiation of immature CD4+ CD8+ T cells into CD4+ or CD8+ mature T cells is unusual in that it is regulated by clonally expressed, somatically generated T-cell receptors (TCRs) of unpredictable fine specificity. Yet, each mature T cell generally retains expression of the co-receptor molecule (CD4 or CD8) that has an MHC-binding property that matches that of its TCR. Two models were proposed initially to explain this remarkable outcome--'instruction' of lineage choice by initial signalling events or 'selection' after a stochastic fate decision that limits further development to cells with coordinated TCR and co-receptor specificities. Aspects of both models now appear to be correct; mistake-prone instruction of lineage choice precedes a subsequent selection step that filters out most incorrect decisions.
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Affiliation(s)
- Ronald N Germain
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-1892, USA.
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22
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Yassai M, Ammon K, Goverman J, Marrack P, Naumov Y, Gorski J. A molecular marker for thymocyte-positive selection: selection of CD4 single-positive thymocytes with shorter TCRB CDR3 during T cell development. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:3801-7. [PMID: 11937532 DOI: 10.4049/jimmunol.168.8.3801] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The generation of the naive T cell repertoire is a direct result of maturation and selection events in the thymus. Although maturation events are judged predominantly on the expression of surface markers, molecular markers, more intimately involved in the selection process, can be informative. We have identified a molecular marker for selection in later stages of maturation in humans. Thymocytes are selected for the expression of TCR beta-chains with shorter CDR3 at the double-positive to single-positive (SP) transition. Here we extend these studies to the mouse and show that the selection phenotype is not related to alpha-chain pairing but is a function of the MHC haplotype. Interestingly, the selection is much more apparent in CD4 SP thymocytes than in CD8 SP cells. This is in contrast to human thymocytes, where the selection is equally apparent in both lineages. The involvement of MHC in the process argues that this is a positive selection stage. The difference in the extent of this selection between the two SP lineages may indicate a class difference in the nature of the TCR-MHC interaction, the role of coreceptors in the selection process, or both.
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MESH Headings
- Animals
- Biomarkers/analysis
- CD4-Positive T-Lymphocytes/immunology
- CD4-Positive T-Lymphocytes/metabolism
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Complementarity Determining Regions/analysis
- Complementarity Determining Regions/blood
- Complementarity Determining Regions/genetics
- Gene Rearrangement, beta-Chain T-Cell Antigen Receptor
- Genes, MHC Class II/physiology
- Immunophenotyping
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Knockout
- Mice, Transgenic
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/metabolism
- Receptors, Antigen, T-Cell, alpha-beta/biosynthesis
- Receptors, Antigen, T-Cell, alpha-beta/blood
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Thymus Gland/cytology
- Thymus Gland/immunology
- Thymus Gland/metabolism
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Affiliation(s)
- Maryam Yassai
- Blood Research Institute, Blood Center of Southeastern Wisconsin, Milwaukee, WI 53201, USA
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23
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Singer A. New perspectives on a developmental dilemma: the kinetic signaling model and the importance of signal duration for the CD4/CD8 lineage decision. Curr Opin Immunol 2002; 14:207-15. [PMID: 11869894 DOI: 10.1016/s0952-7915(02)00323-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Double-positive thymocytes are short-lived bipotential cells whose developmental fate is determined by the specificity of their TCRs. A relatively small number of double-positive thymocytes undergo positive selection in the thymus and these are signaled to differentiate either into CD4(+) or CD8(+) mature T cells. The mechanism by which double-positive thymocytes determine their appropriate CD4/CD8 fate has been the subject of intense theoretical debate and rigorous experimental analysis. In the last year, 'signal duration' has been offered as a replacement for 'signal strength' as a major determinant of the CD4/CD8 decision, a deceptively minor refinement that requires a major change in our understanding of how signaled double-positive thymocytes differentiate into mature T cells. Indeed, the kinetic signaling model provides a radically new perspective on the mechanism by which the CD4/CD8 lineage decision is made.
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Affiliation(s)
- Alfred Singer
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD 20892, USA.
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24
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Abstract
Genetic experiments indicate similarity between binding sites on MHC class I (MHCI) for CD8 and on MHCII for CD4, but the crystal structures of CD8/MHCI and CD4/MHCII complexes suggest critical differences between the interfaces in the two complexes. Biophysical analyses using ectodomains of co-receptors and MHC molecules demonstrate extremely fast kinetics and low-affinity interactions. Experiments with soluble multimeric MHC ligands suggest that CD4 and CD8 may differ in the mechanisms by which they promote the formation of ternary TCR/MHC/co-receptor complexes. Co-receptor-influenced duration of TCR signaling controls thymocyte selection. In naïve T cells, CD4/MHCII interactions may promote T-cell survival. Temporal and spatial analysis of TCR and CD4 co-clustering in the immunological synapse suggests that CD4 recruitment is regulated by the half-life of the initial TCR/MHCII complex. Diverse experimental systems have yielded conflicting data that have helped to formulate revised mechanistic models of co-receptor function.
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Affiliation(s)
- Rolf König
- Department of Microbiology and Immunology and the Sealy Center for Molecular Science, The University of Texas Medical Branch, Galveston, TX 77555-1070, USA
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25
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de la Calle-Martin O, Hernandez M, Ordi J, Casamitjana N, Arostegui JI, Caragol I, Ferrando M, Labrador M, Rodriguez-Sanchez JL, Espanol T. Familial CD8 deficiency due to a mutation in the CD8 alpha gene. J Clin Invest 2001; 108:117-23. [PMID: 11435463 PMCID: PMC209336 DOI: 10.1172/jci10993] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
CD8 glycoproteins play an important role in both the maturation and function of MHC class I-restricted T lymphocytes. A 25-year-old man, from a consanguineous family, with recurrent bacterial infections and total absence of CD8(+) cells, was studied. Ab deficiencies and ZAP-70 and TAP defects were ruled out. A missense mutation (gly90-->ser) in both alleles of the immunoglobulin domain of the CD8 alpha gene was shown to correlate with the absence of CD8 expression found in the patient and two sisters. Conversely, high percentages of CD4(-)CD8(-)TCR alpha beta(+) T cells were found in the three siblings. A novel autosomal recessive immunologic defect characterized by absence of CD8(+) cells is described. These findings may help to further understanding of the role of CD8 molecules in human immune response.
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Affiliation(s)
- O de la Calle-Martin
- Department of Immunology, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
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26
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Abstract
During development, alphabeta T cells undergo positive or negative selection and CD4(+)/CD8(+) lineage commitment-events that have a major impact on the functionality of the T cell repertoire. The precise mechanisms of these differentiative steps remain elusive. Research this year has focused on quantitative models of signaling. For positive selection, the timing and extent of ERK activation may be important. For lineage commitment, the extent of Lck recruitment and activation may be the decisive factor. Next, the search is on for the genes that commit the cell to the fate determined by these quantitative differences in signals.
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Affiliation(s)
- K A Hogquist
- Center for Immunology, University of Minnesota, MMC 334, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
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Reome JB, Johnston DS, Helmich BK, Morgan TM, Dutton-Swain N, Dutton RW. The effects of prolonged administration of 5-bromodeoxyuridine on cells of the immune system. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:4226-30. [PMID: 11035055 DOI: 10.4049/jimmunol.165.8.4226] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have determined the in vivo effect of 5-bromodeoxyuridine (BrdU) administered to mice in the drinking water for various lengths of time on the performance of T and B lymphocytes in a number of experimental protocols. Young mice continuously exposed to BrdU fail to gain weight, and the lymphocytes recovered after a prolonged period of exposure are fewer in number than in control mice. The recovery of normal levels of T and B lymphocytes after irradiation is severely impaired. Ag-specific cells responding to Ag in an adoptive transfer model fail to expand as much in the presence of BrdU as in the absence, and the Ag-specific effectors produced in the presence of BrdU are less able to secrete cytokines upon restimulation in vitro. Polarized populations of Tc1 and Tc2 effectors generated in vitro proliferate less in the presence of BrdU, and the resulting effectors make less cytokines per cell upon restimulation. Thus, the incorporation of BrdU into T or B lymphocytes can, under some circumstances, seriously impair the performance of the labeled cells, and these findings raise a note of caution in the interpretation of studies that make use of long-term exposure to BrdU.
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Affiliation(s)
- J B Reome
- Trudeau Institute, Saranac Lake, NY 12983, USA
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28
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Abstract
Mechanisms of lineage choice represent a challenging problem in developmental biology. Recent studies have shown that different T-cell receptor signals can affect CD4 or CD8 lineage choice. Thus, all the ingredients for instructive mechanisms of lineage fate are in place but other mechanisms cannot be completely ruled out.
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Affiliation(s)
- H von Boehmer
- Harvard Medical School, Dana-Farber Cancer Institute, 44 Binney Street, Boston, Massachusetts 02115, USA.
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