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===Thymus Development===
===Thymus Development===
<pubmed limit=5>Thymus Development</pubmed>
<pubmed limit=5>Thymus Development</pubmed>
==2017==
===Cardiac, mandibular and thymic phenotypical association indicates that cranial neural crest underlies bicuspid aortic valve formation in hamsters===
PLoS One. 2017 Sep 27;12(9):e0183556. doi: 10.1371/journal.pone.0183556. eCollection 2017.
Martínez-Vargas J1, Ventura J1, Machuca Á2, Muñoz-Muñoz F1, Fernández MC2,3, Soto-Navarrete MT2, Durán AC2,3, Fernández B2,3,4.
Abstract
Bicuspid aortic valve (BAV) is the most prevalent human congenital cardiac malformation. It may appear isolated, associated with other cardiovascular malformations, or forming part of syndromes. Cranial neural crest (NC) defects are supposed to be the cause of the spectrum of disorders associated with syndromic BAV. Experimental studies with an inbred hamster model of isolated BAV showed that alterations in the migration or differentiation of the cardiac NC cells in the embryonic cardiac outflow tract are most probably responsible for the development of this congenital valvular defect. We hypothesize that isolated BAV is not the result of local, but of early alterations in the behavior of the NC cells, thus also affecting other cranial NC-derived structures. Therefore, we tested whether morphological variation of the aortic valve is linked to phenotypic variation of the mandible and the thymus in the hamster model of isolated BAV, compared to a control strain. Our results show significant differences in the size and shape of the mandible as well as in the cellular composition of the thymus between the two strains, and in mandible shape regarding the morphology of the aortic valve. Given that both the mandible and the thymus are cranial NC derivatives, and that the cardiac NC belongs to the cephalic domain, we propose that the causal defect leading to isolated BAV during embryonic development is not restricted to local alterations of the cardiac NC cells in the cardiac outflow tract, but it is of pleiotropic or polytopic nature. Our results suggest that isolated BAV may be the forme fruste of a polytopic syndrome involving the cranial NC in the hamster model and in a proportion of affected patients.
PMID: 28953926 PMCID: PMC5617148 DOI: 10.1371/journal.pone.0183556





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Cite this page: Hill, M.A. (2024, March 28) Embryology Thymus Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Thymus_Development

MBoC Figure 24-6. The development and activation of T and B cells | Figure 24-7. Electron micrographs of nonactivated and activated lymphocytes


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Note - This sub-heading shows an automated computer PubMed search using the listed sub-heading term. References appear in this list based upon the date of the actual page viewing. Therefore the list of references do not reflect any editorial selection of material based on content or relevance. In comparison, references listed on the content page and discussion page (under the publication year sub-headings) do include editorial selection based upon relevance and availability. (More? Pubmed Most Recent)


Thymus Embryology

<pubmed limit=5>Thymus Embryology</pubmed>

Thymus Development

<pubmed limit=5>Thymus Development</pubmed>

2017

Cardiac, mandibular and thymic phenotypical association indicates that cranial neural crest underlies bicuspid aortic valve formation in hamsters

PLoS One. 2017 Sep 27;12(9):e0183556. doi: 10.1371/journal.pone.0183556. eCollection 2017.

Martínez-Vargas J1, Ventura J1, Machuca Á2, Muñoz-Muñoz F1, Fernández MC2,3, Soto-Navarrete MT2, Durán AC2,3, Fernández B2,3,4.

Abstract

Bicuspid aortic valve (BAV) is the most prevalent human congenital cardiac malformation. It may appear isolated, associated with other cardiovascular malformations, or forming part of syndromes. Cranial neural crest (NC) defects are supposed to be the cause of the spectrum of disorders associated with syndromic BAV. Experimental studies with an inbred hamster model of isolated BAV showed that alterations in the migration or differentiation of the cardiac NC cells in the embryonic cardiac outflow tract are most probably responsible for the development of this congenital valvular defect. We hypothesize that isolated BAV is not the result of local, but of early alterations in the behavior of the NC cells, thus also affecting other cranial NC-derived structures. Therefore, we tested whether morphological variation of the aortic valve is linked to phenotypic variation of the mandible and the thymus in the hamster model of isolated BAV, compared to a control strain. Our results show significant differences in the size and shape of the mandible as well as in the cellular composition of the thymus between the two strains, and in mandible shape regarding the morphology of the aortic valve. Given that both the mandible and the thymus are cranial NC derivatives, and that the cardiac NC belongs to the cephalic domain, we propose that the causal defect leading to isolated BAV during embryonic development is not restricted to local alterations of the cardiac NC cells in the cardiac outflow tract, but it is of pleiotropic or polytopic nature. Our results suggest that isolated BAV may be the forme fruste of a polytopic syndrome involving the cranial NC in the hamster model and in a proportion of affected patients.

PMID: 28953926 PMCID: PMC5617148 DOI: 10.1371/journal.pone.0183556


2016

Medullary thymic epithelial stem cells: role in thymic epithelial cell maintenance and thymic involution

Immunol Rev. 2016 May;271(1):38-55. doi: 10.1111/imr.12412.

Hamazaki Y1, Sekai M1, Minato N1.

Abstract

The thymus consists of two distinct anatomical regions, the cortex and the medulla; medullary thymic epithelial cells (mTECs) play a crucial role in establishing central T-cell tolerance for self-antigens. Although the understanding of mTEC development in thymic organogenesis as well as the regulation of their differentiation and maturation has improved, the mechanisms of postnatal maintenance remain poorly understood. This issue has a central importance in immune homeostasis and physiological thymic involution as well as autoimmune disorders in various clinicopathological settings. Recently, several reports have demonstrated the existence of TEC stem or progenitor cells in the postnatal thymus, which are either bipotent or unipotent. We identified stem cells specified for mTEC-lineage that are generated in the thymic ontogeny and may sustain mTEC regeneration and lifelong central T-cell self-tolerance. This finding suggested that the thymic medulla is maintained autonomously by its own stem cells. Although several issues, including the relationship with other putative TEC stem/progenitors, remain unclear, further examination of mTEC stem cells (mTECSCs) and their regulatory mechanisms may contribute to the understanding of postnatal immune homeostasis. Possible relationships between decline of mTECSC activity and early thymic involution as well as various autoimmune disorders are discussed.

© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

KEYWORDS: central tolerance; medullary thymic epithelial stem cells; thymic epithelial cells; thymic epithelial stem cells; thymic involution; thymus PMID 27088906 DOI: 10.1111/imr.12412

Fetal thymus size in human pregnancies reveals inverse association with regulatory T cell frequencies in cord blood

J Reprod Immunol. 2016 Feb;113:76-82. doi: 10.1016/j.jri.2015.12.002. Epub 2015 Dec 29.

Diemert A1, Hartwig I2, Pagenkemper M2, Mehnert R2, Hansen G2, Tolosa E3, Hecher K2, Arck P2.

Abstract

OBJECTIVE: To determine fetal thymus growth and its relationship with fetal weight and cord blood T-regulatory cells in a prospective study. Assessment of fetal immune organs by ultrasound could provide a screening approach to identify fetuses at risk of impaired postnatal immunity. STUDY DESIGN AND OUTCOME MEASURES: Thymus size was measured with four ultrasound techniques. The approaches with lowest coefficient of variation (thymus transverse diameter, 3 vessel edge) were used to longitudinally assess fetal and thymus growth in 137 cases at four time points between a gestational age (GA) of 13 and 37 weeks. Cord blood at birth was analyzed by flow-cytometry to evaluate the frequency of regulatory T (Treg) cells. RESULTS AND CONCLUSION: Fetal thymus growth is significantly correlated with fetal weight (GA 23-25 weeks r=0.40, p<0.01; GA 28-30 weeks r=0.21, p=0.04, GA 35-37 weeks r=0.56, p<0.01). We observed an inverse correlation between fetal thymus size at GA 23-25 weeks and cord blood Treg cells (r=0.37, p=0.01). Thymus growth occurs in a linear fashion throughout pregnancy and can be reliably measured using ultrasound. Our findings of an inverse correlation between thymus growth and Treg cells in cord blood suggests a link between fetal growth, thymus development and immune-status at birth. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved. KEYWORDS: Fetal immune system; Fetal thymus; Fetal ultrasound; T-cells

PMID 26851722

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151666

Foxn1 Is Dynamically Regulated in Thymic Epithelial Cells during Embryogenesis and at the Onset of Thymic Involution

PLoS One. 2016 Mar 16;11(3):e0151666. doi: 10.1371/journal.pone.0151666. eCollection 2016.

O'Neill KE1, Bredenkamp N1, Tischner C1, Vaidya HJ1, Stenhouse FH1, Peddie CD1, Nowell CS1, Gaskell T1, Blackburn CC1.

Abstract

Thymus function requires extensive cross-talk between developing T-cells and the thymic epithelium, which consists of cortical and medullary TEC. The transcription factor FOXN1 is the master regulator of TEC differentiation and function, and declining Foxn1 expression with age results in stereotypical thymic involution. Understanding of the dynamics of Foxn1 expression is, however, limited by a lack of single cell resolution data. We have generated a novel reporter of Foxn1 expression, Foxn1G, to monitor changes in Foxn1 expression during embryogenesis and involution. Our data reveal that early differentiation and maturation of cortical and medullary TEC coincides with precise sub-lineage-specific regulation of Foxn1 expression levels. We further show that initiation of thymic involution is associated with reduced cTEC functionality, and proportional expansion of FOXN1-negative TEC in both cortical and medullary sub-lineages. Cortex-specific down-regulation of Foxn1 between 1 and 3 months of age may therefore be a key driver of the early stages of age-related thymic involution.

PMID 26983083 PMCID: PMC4794177 DOI: 10.1371/journal.pone.0151666

2015

Immunohistological analysis of the jun family and the signal transducers and activators of transcription in thymus

Anat Res Int. 2015;2015:541582. doi: 10.1155/2015/541582. Epub 2015 Mar 18.

Papoudou-Bai A1, Barbouti A2, Galani V2, Stefanaki K3, Kanavaros P2.

Abstract

The Jun family and the signal transducers and activators of transcription (STAT) are involved in proliferation and apoptosis. Moreover, c-Jun and STAT3 cooperate to regulate apoptosis. Therefore, we used double immunostaining to investigate the immunotopographical distribution of phospho-c-Jun (p-c-Jun), JunB, JunD, p-STAT3, p-STAT5, and p-STAT6 in human thymus. JunD was frequently expressed by thymocytes with higher expression in medullary compared to cortical thymocytes. p-c-Jun was frequently expressed by cortical and medullary thymic epithelial cells (TEC) and Hassall bodies (HB). p-STAT3 was frequently expressed by TEC with higher expression in cortical compared to medullary TEC and HB. p-c-Jun, JunB, p-STAT3, p-STAT5, and p-STAT6 were rarely expressed by thymocytes. JunB and JunD were expressed by rare cortical TEC with higher expression in medullary TEC. p-STAT5 and p-STAT6 were expressed by rare cortical and medullary TEC. Double immunostaining revealed p-c-Jun and JunD expression in rare CD11c positive dendritic cells. Our findings suggest a notable implication of JunD in the physiology of thymocytes and p-c-Jun and p-STAT3 in the physiology of TEC. The diversity of the immunotopographical distribution and the expression levels of p-c-Jun, JunB, JunD, p-STAT3, p-STAT5, and p-STAT6 indicates that they are differentially involved in the differentiation of TEC, thymocytes, and dendritic cells.

PMID 25866678 [PubMed] PMCID: PMC4381968


2014

Multiple roles for HOXA3 in regulating thymus and parathyroid differentiation and morphogenesis in mouse

Development. 2014 Oct;141(19):3697-708. doi: 10.1242/dev.110833. Epub 2014 Sep 5.

Chojnowski JL1, Masuda K1, Trau HA1, Thomas K2, Capecchi M3, Manley NR4.

Abstract Hoxa3 was the first Hox gene to be mutated by gene targeting in mice and is required for the development of multiple endoderm and neural crest cell (NCC)-derived structures in the pharyngeal region. Previous studies have shown that the Hoxa3 null mutant lacks third pharyngeal pouch derivatives, the thymus and parathyroids by E18.5, and organ-specific markers are absent or downregulated during initial organogenesis. Our current analysis of the Hoxa3 null mutant shows that organ-specific domains did undergo initial patterning, but the location and timing of key regional markers within the pouch, including Tbx1, Bmp4 and Fgf8, were altered. Expression of the parathyroid marker Gcm2 was initiated but was quickly downregulated and differentiation failed; by contrast, thymus markers were delayed but achieved normal levels, concurrent with complete loss through apoptosis. To determine the cell type-specific roles of Hoxa3 in third pharyngeal pouch development, we analyzed tissue-specific mutants using endoderm and/or NCC-specific Cre drivers. Simultaneous deletion with both drivers resulted in athymia at E18.5, similar to the null. By contrast, the individual tissue-specific Hoxa3 deletions resulted in small, ectopic thymi, although each had a unique phenotype. Hoxa3 was primarily required in NCCs for morphogenesis. In endoderm, Hoxa3 temporally regulated initiation of the thymus program and was required in a cell-autonomous manner for parathyroid differentiation. Furthermore, Hoxa3 was required for survival of third pharyngeal pouch-derived organs, but expression in either tissue was sufficient for this function. These data show that Hoxa3 has multiple complex and tissue-specific functions during patterning, differentiation and morphogenesis of the thymus and parathyroids. © 2014. Published by The Company of Biologists Ltd. KEYWORDS: Hoxa3; Mouse; Parathyroid; Thymus PMID 25249461

2013

Thymus involution and regeneration: two sides of the same coin?

Nat Rev Immunol. 2013 Nov;13(11):831-8. doi: 10.1038/nri3534. Epub 2013 Sep 20.

Boehm T, Swann JB. Author information

Abstract In vertebrates, the thymus is the main site of T cell development. The thymus reaches its maximum output during adolescence, after which it shrinks and generates fewer and fewer T cells. Physiological age-related involution of the thymus and failure to recover after injury are associated with impaired cellular immunity; hence, there is considerable interest in developing strategies to combat these deficiencies. In this Opinion article, we briefly review the phylogenetic and ontogenetic hallmarks of thymus development and function, and we discuss experimental models of impaired thymopoiesis and the molecular mechanisms of thymopoietic recovery. At each stage of the discussion we highlight the major gaps in our current knowledge. PMID 24052146

Dynamics of thymus organogenesis and colonization in early human development

Development. 2013 May;140(9):2015-26. doi: 10.1242/dev.087320.

Farley AM, Morris LX, Vroegindeweij E, Depreter ML, Vaidya H, Stenhouse FH, Tomlinson SR, Anderson RA, Cupedo T, Cornelissen JJ, Blackburn CC. Source MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, CRM Building, 5 Little France Drive, Edinburgh EH16 4UU.

Abstract

The thymus is the central site of T-cell development and thus is of fundamental importance to the immune system, but little information exists regarding molecular regulation of thymus development in humans. Here we demonstrate, via spatial and temporal expression analyses, that the genetic mechanisms known to regulate mouse thymus organogenesis are conserved in humans. In addition, we provide molecular evidence that the human thymic epithelium derives solely from the third pharyngeal pouch, as in the mouse, in contrast to previous suggestions. Finally, we define the timing of onset of hematopoietic cell colonization and epithelial cell differentiation in the human thymic primordium, showing, unexpectedly, that the first colonizing hematopoietic cells are CD45(+)CD34(int/-). Collectively, our data provide essential information for translation of principles established in the mouse to the human, and are of particular relevance to development of improved strategies for enhancing immune reconstitution in patients.

PMID 23571219

http://dev.biologists.org/content/140/9/2015.full?sid=540c6d1a-08c1-4a63-a7ea-9409ecc4b940

2012

Modulation of Bmp4 signalling in the epithelial-mesenchymal interactions that take place in early thymus and parathyroid development in avian embryos

Dev Biol. 2012 Jan 15;361(2):208-19. Epub 2011 Oct 28.

Neves H, Dupin E, Parreira L, Le Douarin NM. Source CNRS UPR3294 Laboratoire Neurobiologie et Développement, Institut de Neurobiologie Alfred Fessard, Avenue de la Terrasse 91190 Gif-sur-Yvette Cedex, France. hneves@fm.ul.pt

Abstract

Epithelial-mesenchymal interactions are crucial for the development of the endoderm of the pharyngeal pouches into the epithelia of thymus and parathyroid glands. Here we investigated the dynamics of epithelial-mesenchymal interactions that take place at the earliest stages of thymic and parathyroid organogenesis using the quail-chick model together with a co-culture system capable of reproducing these early events in vitro. The presumptive territories of thymus and parathyroid epithelia were identified in three-dimensionally preserved pharyngeal endoderm of embryonic day 4.5 chick embryos on the basis of the expression of Foxn1 and Gcm2, respectively: the thymic rudiment is located in the dorsal domain of the third and fourth pouches, while the parathyroid rudiment occupies a more medial/anterior pouch domain. Using in vitro quail-chick tissue associations combined with in ovo transplantations, we show that the somatopleural but not the limb bud mesenchyme, can mimic the role of neural crest-derived pharyngeal mesenchyme to sustain development of these glands up to terminal differentiation. Furthermore, mesenchymal-derived Bmp4 appears to be essential to promote early stages of endoderm development during a short window of time, irrespective of the mesenchymal source. In vivo studies using the quail-chick system and implantation of growth factor soaked-beads further showed that expression of Bmp4 by the mesenchyme is necessary during a 24 h-period of time. After this period however, Bmp4 is no longer required and another signalling factor produced by the mesenchyme, Fgf10, influences later differentiation of the pouch endoderm. These results show that morphological development and cell differentiation of thymus and parathyroid epithelia require a succession of signals emanating from the associated mesenchyme, among which Bmp4 plays a pivotal role for triggering thymic epithelium specification. Copyright © 2011 Elsevier Inc. All rights reserved.

PMID 22057081

Evolution of thymus organogenesis

Dev Comp Immunol. 2012 Jan 13. [Epub ahead of print]

Ge Q, Zhao Y. Source Key Laboratory of Medical Immunology, Ministry of Health, Department of Immunology, School of Basic Medical Sciences, Peking University Health Sciences Center, 38 Xue Yuan Road, Beijing 100191, PR China.

Abstract

The thymus is the primary organ for functional T lymphocyte development in jawed vertebrates. A new study in the jawless fish, lampreys, indicates the existence of a primitive thymus in these surviving representatives of the most ancient vertebrates, providing strong evidence of co-evolution of T cells and thymus. This review summarizes the wealth of data that have been generated towards understanding the evolution of the thymus in the vertebrates. Progress in identifying genetic networks and cellular mechanisms that control thymus organogenesis in mammals and their evolution in lower species may inspire the development of new strategies for medical interventions targeting faulty thymus functions. Copyright © 2012. Published by Elsevier Ltd.

PMID 22266420

2011

Thymic involution: where endocrinology meets immunology

Neuroimmunomodulation. 2011;18(5):281-9. Epub 2011 Sep 22.

Calder AE, Hince MN, Dudakov JA, Chidgey AP, Boyd RL. Source Monash Immunology and Stem Cell Laboratories, Monash University, Clayton, Vic., Australia.

Abstract

The decline in immune function with aging represents a major clinical challenge in many disease conditions. It is manifest in many parameters but is essentially linked to the adaptive immune responses. The prediction would be that abnormalities in both T and B lymphocytes underlie the loss of cellular and humoral capacity, respectively. Somewhat surprisingly, this is not reflected in numerical losses but more in alterations at the population and single cell levels. There is a major reduction in naïve T cells with a proportional increase in memory cells, and also a generally reduced function of these cells. While bone marrow function reduces with age, the most obvious reason for the T cell defects is the severe atrophy of the thymus. This is closely aligned with puberty, thereby implicating a major aetiological role for sex steroids in both thymus and immune system deterioration with age. Accordingly surgical or chemical castration (utilizing luteinizing hormone-releasing hormone) blocks sex steroids resulting in profound rejuvenation of the immune system. Copyright © 2011 S. Karger AG, Basel.

PMID 21952680

http://content.karger.com/produktedb/produkte.asp?DOI=000329496&typ=pdf

Mechanisms of thymus organogenesis and morphogenesis

Development. 2011 Sep;138(18):3865-78.

Gordon J, Manley NR. Source Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.

Abstract

The thymus is the primary organ responsible for generating functional T cells in vertebrates. Although T cell differentiation within the thymus has been an area of intense investigation, the study of thymus organogenesis has made slower progress. The past decade, however, has seen a renewed interest in thymus organogenesis, with the aim of understanding how the thymus develops to form a microenvironment that supports T cell maturation and regeneration. This has prompted modern revisits to classical experiments and has driven additional genetic approaches in mice. These studies are making significant progress in identifying the molecular and cellular mechanisms that control specification, early organogenesis and morphogenesis of the thymus.

PMID 21862553


http://dev.biologists.org/content/138/18/3865/F2.expansion.html

A focused in situ hybridization screen identifies candidate transcriptional regulators of thymic epithelial cell development and function

PLoS One. 2011;6(11):e26795. Epub 2011 Nov 7.

Wei Q, Condie BG. Source Department of Genetics, University of Georgia, Athens, Georgia, United States of America.

Abstract

BACKGROUND: Thymic epithelial cells (TECs) are necessary for normal T cell development. Currently, one transcription factor, Foxn1 is known to be necessary for the progression of fetal TEC differentiation. However, some aspects of fetal TEC differentiation occur in Foxn1 mutants, suggesting the existence of additional transcriptional regulators of TEC differentiation. The goal of this study was to identify some of the additional candidate transcription factors that may be involved in the specification and/or differentiation of TECs during fetal development. METHODOLOGY/PRINCIPAL FINDINGS: We identified candidate fetal TEC transcriptional regulators via data and text mining. From our data mining we selected the transcription factors Foxg1, Isl1, Gata3, Nkx2-5, Nkx2-6 and Sox2 for further studies. Whole mount in situ hybridizations confirmed the expression of these transcription factors within subdomains of the third pharyngeal pouch from E9.5-E10.5. By E11.5 days Foxg1 and Isl1 transcripts were the only mRNAs from this group of genes detected exclusively within the thymus domain of the third pouch. Based on this initial in situ hybridization analysis, we focused on defining the expression of Foxg1 and Isl1 during multiple stages of thymus development and TEC differentiation. We found that Foxg1 and Isl1 are specifically expressed in differentiating TECs during fetal and postnatal stages of thymus development. In addition, we found differential expression of Islet1 and Foxn1 within the fetal and postnatal TEC population. CONCLUSIONS/SIGNIFICANCE: Our studies have identified two developmental transcription factors that are excellent candidate regulators of thymic epithelial cell specification and differentiation during fetal development. Our results suggest that Foxg1 and Isl1 may play a role in the regulation of TEC differentiation during fetal and postnatal stages. Our results also demonstrate heterogeneity of TECs marked by the differential expression of transcription factors, potentially providing new insights into the regulation of TEC differentiation.

PMID 22087235

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0026795

Foxn1 regulates lineage progression in cortical and medullary thymic epithelial cells but is dispensable for medullary sub lineage divergence

PLoS Genet. 2011 Nov;7(11):e1002348. Epub 2011 Nov 3.

Nowell CS, Bredenkamp N, Tetélin S, Jin X, Tischner C, Vaidya H, Sheridan JM, Stenhouse FH, Heussen R, Smith AJ, Blackburn CC. Source MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.

Abstract

The forkhead transcription factor Foxn1 is indispensable for thymus development, but the mechanisms by which it mediates thymic epithelial cell (TEC) development are poorly understood. To examine the cellular and molecular basis of Foxn1 function, we generated a novel and revertible hypomorphic allele of Foxn1. By varying levels of its expression, we identified a number of features of the Foxn1 system. Here we show that Foxn1 is a powerful regulator of TEC differentiation that is required at multiple intermediate stages of TE lineage development in the fetal and adult thymus. We find no evidence for a role for Foxn1 in TEC fate-choice. Rather, we show it is required for stable entry into both the cortical and medullary TEC differentiation programmes and subsequently is needed at increasing dosage for progression through successive differentiation states in both cortical and medullary TEC. We further demonstrate regulation by Foxn1 of a suite of genes with diverse roles in thymus development and/or function, suggesting it acts as a master regulator of the core thymic epithelial programme rather than regulating a particular aspect of TEC biology. Overall, our data establish a genetics-based model of cellular hierarchies in the TE lineage and provide mechanistic insight relating titration of a single transcription factor to control of lineage progression. Our novel revertible hypomorph system may be similarly applied to analyzing other regulators of development.

PMID 22072979

2010

A novel role for transcription factor Lmo4 in thymus development through genetic interaction with Cited2

Dev Dyn. 2010 Jul;239(7):1988-94.

Michell AC, Bragança J, Broadbent C, Joyce B, Franklyn A, Schneider JE, Bhattacharya S, Bamforth SD.

Department of Cardiovascular Medicine, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, United Kingdom. Abstract Deletion of the transcriptional modulator Cited2 in the mouse results in embryonic lethality, cardiovascular malformations, adrenal agenesis, cranial ganglia fusion, exencephaly, and left-right patterning defects, all seen with a varying degree of penetrance. The phenotypic heterogeneity, observed on different genetic backgrounds, indicates the existence of both genetic and environmental modifiers. Mice lacking the LIM domain-containing protein Lmo4 share specific phenotypes with Cited2 null embryos, such as embryonic lethality, cranial ganglia fusion, and exencephaly. These shared phenotypes suggested that Lmo4 may be a potential genetic modifier of the Cited2 phenotype. Examination of Lmo4-deficient embryos revealed partially penetrant cardiovascular malformations and hypoplastic thymus. Examination of Lmo4;Cited2 compound mutants indicated that there is a genetic interaction between Cited2 and Lmo4 in control of thymus development. Our data suggest that this may occur, in part, through control of expression of a common target gene, Tbx1, which is necessary for normal thymus development.

(c) 2010 Wiley-Liss, Inc. PMID: 20549734

Thymic stromal lymphopoietin

Ann N Y Acad Sci. 2010 Jan;1183:13-24.

He R, Geha RS.

Division of Immunology, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.

Abstract

Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine expressed in skin, gut, lungs, and thymus. TSLP signals via a TSLP receptor (TSLPR), a heterodimer of the IL-7 receptor alpha chain and the TSLPR chain. The TSLPR chain is closely related to the common receptor gamma chain that is expressed on a wide range of cell types in the adaptive and innate immune system. TSLP exerts a profound influence on the polarization of dendritic cells to drive T helper (Th) 2 cytokine production. TSLP also directly promotes T-cell proliferation in response to T-cell receptor activation and Th2 cytokine production and supports B-cell expansion and differentiation. TSLP further amplifies Th2 cytokine production by mast cells and natural killer T cells. These properties confer on TSLP a critical role in driving Th2-mediated inflammation. This role is supported by the finding that TSLP expression is upregulated in keratinocytes of atopic dermatitis skin lesions and in bronchial epithelial cells in asthma.

PMID: 20146705

http://www.ncbi.nlm.nih.gov/pubmed/20146705

2009

Ultrasonographic measurement of thymus size in IUGR fetuses: a marker of the fetal immunoendocrine response to malnutrition

Ultrasound Obstet Gynecol. 2009 Apr;33(4):421-6.

Cromi A, Ghezzi F, Raffaelli R, Bergamini V, Siesto G, Bolis P. Source Department of Obstetrics and Gynecology, University of Insubria, Varese, Italy. antonellacromi@libero.it Abstract OBJECTIVE: To test the hypothesis that intrauterine growth restriction (IUGR) is associated with decreased thymus size in the human fetus. METHODS: The thymus perimeter was measured in 60 consecutive IUGR fetuses at prenatal ultrasound examination. IUGR was defined as an abdominal circumference (AC) <5(th) centile. Sixty controls were identified by selection of the next consecutive appropriately grown fetus of similar gestational age (+/-1 week). To exclude fetal size effects, ratios between thymus perimeter and fetal biometry measurements including biparietal diameter (BPD), AC and femur length (FL), as well as estimated fetal weight (EFW) were compared between IUGR fetuses and controls. RESULTS: The proportion of fetuses with thymus perimeter <5(th) centile for gestation was significantly higher in IUGR fetuses than in controls (58/60 vs. 7/60, P < 0.0001). The mean thymus perimeter/BPD ratio (0.87 +/- 0.20 vs. 1.13 +/- 0.13, P < 0.0001), thymus perimeter/AC ratio (0.28 +/- 0.06 vs. 0.35 +/- 0.03, P < 0.0001), thymus perimeter/FL ratio (1.18 +/- 0.26 vs. 1.51 +/- 0.19, P < 0.001) and thymus perimeter/EFW ratio (0.05 +/- 0.01 vs. 0.06 +/- 0.01, P = 0.02) were significantly lower in IUGR fetuses than in controls. There was a significant positive correlation between the observed-to-expected mean for gestation thymus perimeter ratio and the enrollment-to-delivery interval (r = 0.44, P < 0.001). CONCLUSION: IUGR is associated with a disproportionately small thymus. This supports the hypothesis that thymic involution may be part of the fetal neuroendocrine response to intrauterine starvation. (c) 2009 ISUOG. Published by John Wiley & Sons, Ltd.

PMID 19306477

Gene expression profile of the third pharyngeal pouch reveals role of mesenchymal MafB in embryonic thymus development

Blood. 2009 Mar 26;113(13):2976-87. Epub 2009 Jan 22.

Sultana DA, Tomita S, Hamada M, Iwanaga Y, Kitahama Y, Khang NV, Hirai S, Ohigashi I, Nitta S, Amagai T, Takahashi S, Takahama Y.

Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan.

Abstract

The thymus provides a microenvironment that induces the differentiation of T-progenitor cells into functional T cells and that establishes a diverse yet self-tolerant T-cell repertoire. However, the mechanisms that lead to the development of the thymus are incompletely understood. We report herein the results of screening for genes that are expressed in the third pharyngeal pouch, which contains thymic primordium. Polymerase chain reaction (PCR)-based cDNA subtraction screening for genes expressed in microdissected tissues of the third pharyngeal pouch rather than the second pharyngeal arch yielded one transcription factor, MafB, which was predominantly expressed in CD45(-)IA(-)PDGFRalpha(+) mesenchymal cells and was detectable even in the third pharyngeal pouch of FoxN1-deficient nude mice. Interestingly, the number of CD45(+) cells that initially accumulated in the embryonic thymus was significantly decreased in MafB-deficient mice. Alterations of gene expression in the embryonic thymi of MafB-deficient mice included the reduced expression of Wnt3 and BMP4 in mesenchymal cells and of CCL21 and CCL25 in epithelial cells. These results suggest that MafB expressed in third pharyngeal pouch mesenchymal cells critically regulates lymphocyte accumulation in the embryonic thymus.

PMID: 19164599

2008

  • Rodewald HR. Thymus organogenesis. Annu Rev Immunol. 2008;26:355-88.

Neural crest origin of perivascular mesenchyme in the adult thymus

J Immunol. 2008 Apr 15;180(8):5344-51.

Müller SM, Stolt CC, Terszowski G, Blum C, Amagai T, Kessaris N, Iannarelli P, Richardson WD, Wegner M, Rodewald HR.

Institute for Immunology, University of Ulm, Ulm, Germany.

Abstract

The endodermal epithelial thymus anlage develops in tight association with neural crest (NC)-derived mesenchyme. This epithelial-NC interaction is crucial for thymus development, but it is not known how NC supports thymus development or whether NC cells or their progeny make any significant contribution to the adult thymus. By nude mouse blastocyst complementation and by cell surface phenotype, we could previously separate thymus stroma into Foxn1-dependent epithelial cells and a Foxn1-independent mesenchymal cell population. These mesenchymal cells expressed vascular endothelial growth factor-A, and contributed to thymus vascularization. These data suggested a physical or functional association with thymic blood vessels, but the origin, location in the thymus, and function of these stromal cells remained unknown. Using a transgenic mouse expressing Cre recombinase in premigratory NC (Sox10-Cre), we have now fate-mapped the majority of these adult mesenchymal cells to a NC origin. NC-derived cells represent tightly vessel-associated pericytes that are sandwiched between endothelium and epithelium along the entire thymus vasculature. The ontogenetic, phenotypic, and positional definition of this distinct perivascular mesenchymal compartment provides a cellular basis for the role of NC in thymus development and possibly maintenance, and might be useful to address properties of the endothelial-epithelial barrier in the adult thymus.

PMID: 18390716

http://www.jimmunol.org/content/180/8/5344.long

2007

  • Boehm T, Bleul CC. The evolutionary history of lymphoid organs. Nat Immunol. 2007 Feb;8(2):131-5. "During vertebrate evolution, primary lymphoid organs appeared earlier than secondary lymphoid organs. Among the sites of primary lymphopoiesis during evolution and ontogeny, those for B cell differentiation have differed considerably, although they often have had myelolymphatic characteristics. In contrast, only a single site for T cell differentiation has occurred, exclusively the thymus."
  • Assarsson E, Chambers BJ, Hogstrand K, Berntman E, Lundmark C, Fedorova L, Imreh S, Grandien A, Cardell S, Rozell B, Ljunggren HG. Severe defect in thymic development in an insertional mutant mouse model. J Immunol. 2007 Apr 15;178(8):5018-27.

Ontogeny of intrinsic innervation in the human thymus and spleen

J Histochem Cytochem. 2007 Aug;55(8):813-20. Epub 2007 Apr 16.

Anagnostou VK, Doussis-Anagnostopoulou I, Tiniakos DG, Karandrea D, Agapitos E, Karakitsos P, Kittas C.

Laboratory of Histology and Embryology, Medical School, National and Kapodistrian University of Athens, 75 M. Asias Str, 11527 Athens, Greece. aisantha@hotmail.com Abstract The ontogeny of the innervation of human lymphoid organs has not been studied in detail. Our aim was to assess the nature and distribution of parenchymal nerves in human fetal thymus and spleen. We used the peroxidase immunohistochemical technique with antibodies specific to neuron-specific enolase (NSE), neurofilaments (NF), PGP9.5, S100 protein, and tyrosine hydroxylase (TH) and evaluated our results with image analysis. In human fetal thymus, NSE-, NF-, S100-, PGP9.5-, and TH-positive nerves were identified associated with large blood vessels from 18 gestational weeks (gw) onwards, increasing in density during development. Their branches penetrated the septal areas at 20 gw, reaching the cortex and the corticomedullary junction between 20 and 23 gw. Few nerve fibers were seen in the medulla in close association with Hassall's corpuscles. In human fetal spleen, NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers were localized in the connective tissue surrounding the splenic artery at 18 gw. Perivascular NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers were seen extending into the white pulp, mainly in association with the central artery and its branches, increasing in density during gestation. Scattered NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers and endings were localized in the red pulp from 18 gw onward. The predominant perivascular distribution of most parenchymal nerves implies that thymic and splenic innervation may play an important functional role during intrauterine life.

PMID 17438351

2006

Cellular and molecular events during early thymus development

Holländer G, Gill J, Zuklys S, Iwanami N, Liu C, Takahama Y. Immunol Rev. 2006 Feb;209:28-46. Review.

The thymic stromal compartment consists of several cell types that collectively enable the attraction, survival, expansion, migration, and differentiation of T-cell precursors. The thymic epithelial cells constitute the most abundant cell type of the thymic microenvironment and can be differentiated into morphologically, phenotypically, and functionally separate subpopulations of the postnatal thymus. All thymic epithelial cells are derived from the endodermal lining of the third pharyngeal pouch. Very soon after the formation of a thymus primordium and prior to its vascularization, thymic epithelial cells orchestrate the first steps of intrathymic T-cell development, including the attraction of lymphoid precursor cells to the thymic microenvironment. The correct segmentation of pharyngeal epithelial cells and their subsequent crosstalk with cells in the pharyngeal arches are critical prerequisites for the formation of a thymus anlage. Mutations in several transcription factors and their target genes have been informative to detail some of the complex mechanisms that control the development of the thymus anlage.

PMID: 16448532


The thymus is a common target organ in infectious diseases

PLoS Pathog. 2006 Jun;2(6):e62.

Savino W. Source Laboratory on Thymus Research, Department of Immunology, Oswaldo Cruz Institute, Inserm-Fiocruz Associated Laboratory of Immunology, Oswaldo Cruz Foundation, Rio de Janeiro, RJ, Brazil. savino@fiocruz.br

Abstract

Infectious disease immunology has largely focused on the effector immune response, changes in the blood and peripheral lymphoid organs of infected individuals, and vaccine development. Studies of the thymus in infected individuals have been neglected, although this is progressively changing. The thymus is a primary lymphoid organ, able to generate mature T cells that eventually colonize secondary lymphoid organs, and is therefore essential for peripheral T cell renewal. Recent data show that normal thymocyte development and export can be altered as a result of an infectious disease. One common feature is the severe atrophy of the infected organ, mainly due to the apoptosis-related depletion of immature CD4+CD8+ thymocytes. Additionally, thymocyte proliferation is frequently diminished. The microenvironmental compartment of the thymus is also affected, particularly in acute infectious diseases, with a densification of the epithelial network and an increase in the deposition of extracellular matrix. In the murine model of Chagas disease, intrathymic chemokine production is also enhanced, and thymocytes from Trypanosoma cruzi-infected mice exhibit greater numbers of cell migration-related receptors for chemokines and extracellular matrix, as well as increased migratory responses to the corresponding ligands. This profile is correlated with the appearance of potentially autoreactive thymus-derived immature CD4+CD8+ T cells in peripheral organs of infected animals. A variety of infectious agents--including viruses, protozoa, and fungi--invade the thymus, raising the hypothesis of the generation of central immunological tolerance for at least some of the infectious agent-derived antigens. It seems clear that the thymus is targeted in a variety of infections, and that such targeting may have consequences on the behavior of peripheral T lymphocytes. In this context, thymus-centered immunotherapeutic approaches potentially represent a new tool for the treatment of severe infectious diseases.

PMID 16846255 PMC1483230


Introduction

Embryonic origins of the endocrine organs of the neck

The thymus has two origins for the lymphoid thymocytes and the thymic epithelial cells. The thymic epithelium begins as two flask-shape endodermal diverticula that form from the third pharyngeal pouch and extend lateralward and backward into the surrounding mesoderm and neural crest-derived mesenchyme in front of the ventral aorta. The immune system T cells are essential for responses against infections and much research concerns the postnatal development of T cells within the thymus.

Endocrine Links: Introduction | BGD Lecture | Science Lecture | Lecture Movie | pineal | hypothalamus‎ | pituitary | thyroid | parathyroid | thymus | pancreas | adrenal | endocrine gonad‎ | endocrine placenta | other tissues | Stage 22 | endocrine abnormalities | Hormones | Category:Endocrine
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1903 Islets of Langerhans | 1903 Pig Adrenal | 1904 interstitial Cells | 1908 Pancreas Different Species | 1908 Pituitary | 1908 Pituitary histology | 1911 Rathke's pouch | 1912 Suprarenal Bodies | 1914 Suprarenal Organs | 1915 Pharynx | 1916 Thyroid | 1918 Rabbit Hypophysis | 1920 Adrenal | 1935 Mammalian Hypophysis | 1926 Human Hypophysis | 1927 Adrenal | 1927 Hypophyseal fossa | 1930 Adrenal | 1932 Pineal Gland and Cysts | 1935 Hypophysis | 1935 Pineal | 1937 Pineal | 1935 Parathyroid | 1940 Adrenal | 1941 Thyroid | 1950 Thyroid Parathyroid Thymus | 1957 Adrenal

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Some Recent Findings

  • Decision checkpoints in the thymus[1]"The development of T cells in the thymus involves several differentiation and proliferation events, during which hematopoietic precursors give rise to T cells ready to respond to antigen stimulation and undergo effector differentiation."

Thymus Development

Developing Human (stage 22)
Developing Human Thymus (stage 22)
  • Endoderm - third pharyngeal pouch
  • Week 6 - diverticulum elongates, hollow then solid, ventral cell proliferation
  • Thymic primordia - surrounded by neural crest mesenchyme, epithelia/mesenchyme interaction
  • Thymus - bone-marrow lymphocyte precursors become thymocytes, and subsequently mature into T lymphocytes (T cells)
  • Thymus hormones - thymosins stimulate the development and differentiation of T lymphocytes
Stage 13 image 058.jpg Stage 22 image 071.jpg
B2 Pharyngeal Arch Pouches 3 and 4 (stage 13) D1 Developing Human Thymus (stage 22)

Thymus Involution

A postnatal process defined as a decrease in the size, weight and activity of the gland with advancing age. In a recent review[2], thymic involution was described as a result of high levels of circulating sex hormones, in particular during puberty, and a lower population of precursor cells from the bone marrow and finally changes in the thymic microenvironment.

References

  1. <pubmed>20644572</pubmed>
  2. <pubmed>20354268 </pubmed>


Reviews

<pubmed>19582736</pubmed> <pubmed>18304000</pubmed> <pubmed>17876091</pubmed> <pubmed>16448532</pubmed>

Articles

<pubmed>17625108</pubmed>


Adult Histology

Terms

  • Hassall's corpuscle - thymic corpuscle.
  • Thymic corpuscle (=Hassall's corpuscle) a mass of concentric epithelioreticular cells found in the thymus. The number present and size tend to increase with thymus age. (see classical description of Hammar, J. A. 1903 Zur Histogenese und Involution der Thymusdriise. Anat. Anz., 27: 1909 Fiinfzig Jahre Thymusforschung. Ergebn. Anat. Entwickl-gesch. 19: 1-274.)
  • thymic epitheliocytes - reticular cells located in the thymus cortex that ensheathe the cortical capillaries, creating and maintain the microenvironment necessary for the development of T-lymphocytes in the cortex.
  • T lymphocyte (cell) - named after thymus, where they develop, the active cell is responsible for cell-mediated immunity. (More? Electron micrographs of nonactivate and activated lymphocytes)