Neurohypophysial Receptor Gene Expression by Thymic T Cell Subsets and Thymic T Cell Lymphoma Cell Lines

in Clinical & Developmental Immunology (2004), 11(1), 45-51

Neurohypophysial oxytocin (OT) and vasopressin (VP) genes are transcribed in thymic epithelium, while immature T lymphocytes express functional neurohypophysial receptors. Neurohypophysial receptors ... [more ▼]

Neurohypophysial oxytocin (OT) and vasopressin (VP) genes are transcribed in thymic epithelium, while immature T lymphocytes express functional neurohypophysial receptors. Neurohypophysial receptors belong to the G protein-linked seven-transmembrane receptor superfamily and are encoded by four distinct genes, OTR, V1R, V2R and V3R. The objective of this study was to identify the nature of neurohypophysial receptor in thymic T cell subsets purified by immunomagnetic selection, as well as in murine thymic lymphoma cell lines RL12-NP and BW5147. OTR is transcribed in all thymic T cell subsets and T cell lines, while V3R transcription is restricted to CD4+CD8+ and CD8+ thymic cells. Neither V1R nor V2R transcripts are detected in any kind of T cells. The OTR protein was identified by immunocytochemistry on thymocytes freshly isolated from C57BL/6 mice. In murine fetal thymic organ cultures, a specific OTR antagonist does not modify the percentage of T cell subsets, but increases late T cell apoptosis further evidencing the involvement of OT/OTR signaling in the control of T cell proliferation and survival. According to these data, OTR and V3R are differentially expressed during T cell ontogeny. Moreover, the restriction of OTR transcription to T cell lines derived from thymic lymphomas may be important in the context of T cell leukemia pathogenesis and treatment. [less ▲]

Presentation of neuroendocrine self in the thymus: toward a novel type of vaccine/immunotherapy

in Drug Design Reviews - Online (2004), 1

Slightly after the emergence some 400 millions years ago of the first signs of adaptive immune response, tolerogenic pathways developed in order to preserve the integrity of self from potential autoimmune ... [more ▼]

Slightly after the emergence some 400 millions years ago of the first signs of adaptive immune response, tolerogenic pathways developed in order to preserve the integrity of self from potential autoimmune toxicity. Amongst those tolerogenic pathways, the thymus occupies a central place both by deleting self-reactive T cells that are produced in the thymus during random recombination of gene segments encoding the variable parts of the T-cell receptor for antigen (TCR) (negative selection), and by generating self-antigen specific regulatory T cells (Tr). A repertoire of neuroendocrine-related genes are transcribed by thymic stromal cells — epithelial and ‘nurse’ cells (TEC/TNC), dendritic cells (DC) and macrophages (MF) — in such a way that a dominant protein precursor is expressed in the thymus environment. Oxytocin (OT) and neurokinin A (NKA) are the dominant thymic precursors for the neurohypophysial hormone and tachykinin families, respectively. With regard to the insulin gene family, all members are transcribed following a precise cell topography and hierarchy in the profile of gene expression: IGF2 (TEC/TNC) > IGF1 (MF) >> INS (medullary TEC and/or DC). This hierarchy implies that IGF-2 is more tolerated than IGF-1, and much more than Insulin (Ins). The low level of INS transcription in the thymus also explains why Ins displays immunogenic properties, as well as the significant prevalence (±40%) of anti-Ins autoantibodies in the general population. Ins administration failed in providing tolerance or protection toward islet ß cells in type 1 diabetes (T1D). In contrast, the presentation of IGF-2 B11-25, the homologous sequence of Ins B9-23, to peripheral blood mononuclear cells (PBMC) isolated from DQ8+ T1D adolescents significantly increases IL-10 secretion and IL10 expression. Given the potent regulatory/suppressive properties of IL-10 on the autoimmune response toward islet ß cells, these data support that IGF-2 derived sequences constitute a strong basis for the development of an antigen-specific driven tolerogenic approach for T1D prevention and/or cure. [less ▲]

Coxsackievirus B4 infection of human fetal thymus cells

in Journal of Virology (2004), 78(18), 9854-9861

The infection of human fetal thymus organ cultures (FTOC) with coxsackievirus B4 E2 (CVB4 E2) was investigated. Both positive- and negative-strand viral RNA were detected by real-time quantitative reverse ... [more ▼]

The infection of human fetal thymus organ cultures (FTOC) with coxsackievirus B4 E2 (CVB4 E2) was investigated. Both positive- and negative-strand viral RNA were detected by real-time quantitative reverse transcription-PCR (RT-PCR) in CVB4 E2-infected FTOC, which supported high yields of virus production (similar to10(6) 50% tissue culture infective doses/ml), and in flow-sorted thymocyte populations for 7 days after inoculation. Cortical CD4(+) CD8(+) thymocytes were found to be the principal targets of infection. Inoculation of human FTOC with CVB4 E2 led to a marked and progressive depletion of immature thymocytes (CD4(+) CD8(+) cells) with no enhancement of Annexin V-positive cells. CVB4 E2 replication caused significant major histocompatibility complex (MHC) class I upregulation on these cells. MHC class I upregulation was correlated with positive- and negative-strand RNA quantitative detection and the release of infectious particles. In addition, chloroquine treatment of FTOC and single-thymocyte suspensions suggested that MHC class I upregulation on thymocytes was the result of direct infection rather than caused by production of soluble factors such as alpha interferon. Thus, CVB4 E2 can infect human fetal thymocytes, which subsequently results in quantitative and qualitative abnormalities of these cells. [less ▲]

Thymus and T cells

in Smith, Barry H.; Adelman, George (Eds.) Encyclopedia of Neuroscience, 3rd Edition (2004)

Evidence for intimate interconnections between the three major systems of cell communication, the nervous, endocrine and immune systems, has opened important novel research perspectives. Neuroimmune ... [more ▼]

Evidence for intimate interconnections between the three major systems of cell communication, the nervous, endocrine and immune systems, has opened important novel research perspectives. Neuroimmune-endocrine interactions are now established as crucial factors for the control of body development and homeostasis. In distant species and invertebrates, the foundations of both the neuroendocrine system and innate immunity were coexisting until now without any apparent problem. Some 400 millions years ago, in a relatively short period after agnathan fishes (e.g., hagfish and lamprey), adaptive immunity emerged in the first gnathostomes, cartilaginous fishes (e.g., shark and ray). Somatic recombination machinery characterizes adaptive immunity and is responsible for the random generation of the huge diversity of immune receptors able to recognize infectious antigens. The emergence of this novel form of immune defenses exerted a so potent pressure that structures and mechanisms developed along the paths of lymphocyte traffic to impose immunological self-tolerance, that is, the inability of the immune system to attack the host organism. Together with the generation of diversity and memory, self-tolerance constitutes a fundamental property of the immune system. The progressive rise in the level of immune diversity and complexity also explains why self-tolerance failures (i.e., organ-specific autoimmune diseases) were increasingly detected during evolution, the maximum being currently observed in the human species. The first thymus appeared in cartilaginous fishes (chondrichthyes), concomitantly with the emergence of rudimental forms of adaptive immunity. Though some forms of tolerance induction already takes place in primary hemopoietic sites (fetal liver and bone marrow), antigen-dependent B-cell tolerance is primarily due to an absence of T-cell help. Among all lymphoid structures, the thymus is the only organ specialized in the establishment of central self-tolerance. The thymus crucially stands at the crossroad between the immune and neuroendocrine systems. In this organ responsible for thymopoiesis—T-cell generation—(Kong et al., 1998), the neuroendocrine system regulates the process of T-cell differentiation from the very early stages. In addition, T lymphocytes undergo inside the thymus a complex educative process that establishes central T-cell self-tolerance of neuroendocrine principles (Geenen et al., 1992; Martens et al., 1996). Within the thymus, a confrontation permanently occurs between previously established neuroendocrine principles and a recent system equipped with recombination machinery promoting stochastic generation of response diversity. Contrary to a previous assumption, the thymus functions throughout life (Poulin et al., 1999; Geenen et al., 2003) and plays a fundamental role in the recovery of a competent T-cell repertoire after intensive chemotherapy or during highly active antiretroviral therapy (Mackall et al., 1995; Douek et al., 1998). [less ▲]

Role of the thymus in the development of tolerance and autoimmunity towards the neuroendocrine system

in Annals of the New York Academy of Sciences (2003), 992

The thymus is the unique lymphoid organ inside which a confrontation occurs throughout life between neuroendocrine self-antigens and a recently evolved system with original recombination machinery driving ... [more ▼]

The thymus is the unique lymphoid organ inside which a confrontation occurs throughout life between neuroendocrine self-antigens and a recently evolved system with original recombination machinery driving random generation of immune response diversity. Through transcription of neuroendocrine genes in the thymus stromal network and expression of cognate receptors by immature T cells, the neuroendocrine system regulates early T cell differentiation. In addition and more specifically, intrathymic presentation of neuroendocrine self-antigens by, or in close association with, major histocompatibility complex (MHC) proteins is responsible for the establishment of central immune self-tolerance of neuroendocrine principles. All members of the insulin gene (INS) family are expressed in the thymus stroma according to a precise hierarchy and cell topography: IGF2 (thymic epithelial cells) > IGF1 (thymic macrophages) much greater than INS (thymic medullary epithelial cells and/or dendritic cells). Given this hierarchical pattern in gene expression, the protein IGF-2 is more tolerated than INS. Igf2 transcription is defective in the thymus of bio-breeding (BB) rat, one animal model of type 1 diabetes (T1DM). This thymus-specific defect in Igf2 expression may explain both the absence of central tolerance to INS-secreting beta cells and the lymphopenia (including lack of regulatory RT6(+) T cells) in diabetes-prone BB rats. INS B:9-23 and the homologous sequence of IGF-2 compete for binding to DQ8, an MHC class II allele conferring major susceptibility to T1DM. In young DQ8(+) T1DM patients, INS B:9-23 presentation by DQ8 elicits a dominant IFN-gamma secretion by isolated PBMCs, whereas presentation of the IGF-2 self-antigen promotes a dominant regulatory interleukin-10 secretion. These data demonstrate that opposite immune responses are driven by MHC presentation of a self-antigen (here, IGF-2) and an autoantigen (INS, as "altered" self). The important tolerogenic properties of thymic self-antigens deserve now to be exploited for prevention and/or cure of devastating autoimmune diseases such as T1DM. [less ▲]

Thymic IGF-2 and central self-tolerance of the insulin family: a basis for the development of a negative vaccine against type 1 diabetes

Conference (2003, March)

Virus infections in pathogenesis of type 1 diabetes

in International Diabetes Monitor (2003), 14

Thymic IGF-2 and central self-tolerance of the insulin family: a basis for the development of a negative vaccine against type 1 diabetes

in Diabetologia (2003), 46 (Suppl. 2)

Thymic pathways to the central T cell self-tolerance of neuroendocrine principles: Implications for a tolerogenic approach of autoimmunity

Conference (2002, October)

La fenêtre implantatoire

in Journal de Gynécologie, Obstétrique et Biologie de la Reproduction (2002), 31(5), 440-55

The implantation window. Background. Embryo implantation is a complex event involving apposition followed by adhesion of the blastocyst to the maternal endometrium, and finally invasion of this ... [more ▼]

The implantation window. Background. Embryo implantation is a complex event involving apposition followed by adhesion of the blastocyst to the maternal endometrium, and finally invasion of this endometrium. Though implantation could occur in any human tissue, the endometrium is the only tissue where embryo implantation cannot occur except during a restricted period called the implantation window. During this window, the endometrium is highly receptive to the embryo. Material and methods. We reviewed the literature concerning the different factors involved in improved endometrial receptivity and implantation. Results. Maternal - embryo crosstalk is favored by the implantation window. Endometrial receptivity results from the acquisition of ligands or receptors facilitating apposition, then adhesion of the embryo, or from the loss of components preventing it. The molecular basis of the implantation window remains to be defined. Conclusion. Despite progress in assisted reproduction technologies, the lack of control of implantation remains a major obstacle to successful pregnancy. It is of prime importance to determine the characteristic features of a receptive endometrium and, among the many markers proposed by in vitro studies, to analyze in humans those demonstrated by knock-out experiments to play a crucial role in mice. [less ▲]