Free Access

Thymus organ cultures and T-cell receptor repertoire development

G. Anderson

Department of Anatomy, MRC Centre for Immune Regulation, Division of Infection and Immunity, Medical School, University of Birmingham, Birmingham, UK

Search for more papers by this author

E. J. Jenkinson,

E. J. Jenkinson

Department of Anatomy, MRC Centre for Immune Regulation, Division of Infection and Immunity, Medical School, University of Birmingham, Birmingham, UK

Search for more papers by this author

G. Anderson,

G. Anderson

Department of Anatomy, MRC Centre for Immune Regulation, Division of Infection and Immunity, Medical School, University of Birmingham, Birmingham, UK

Search for more papers by this author

E. J. Jenkinson,

E. J. Jenkinson

Department of Anatomy, MRC Centre for Immune Regulation, Division of Infection and Immunity, Medical School, University of Birmingham, Birmingham, UK

Search for more papers by this author

First published: 09 October 2008

https://doi.org/10.1046/j.1365-2567.2000.00067.x

Citations: 13

Dr Graham Anderson, Department of Anatomy, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.

Share a link

Email
Wechat
Bluesky

Introduction

T cells bearing the αβ form of the T-cell receptor (αβTCR) play a central role in the immune response through the execution of a number of specialized functions, all of which are dependent upon TCR-mediated recognition of antigenic peptide fragments presented by major histocompatibility complex (MHC) molecules.^1,2 While CD8⁺ cells act as direct mediators of cytotoxic killing through recognition of antigen presented by MHC class I molecules, CD4⁺ cells recognize antigen presented by MHC class II molecules and perform a range of regulatory functions involving contact and/or cytokine-mediated effects. These functions include the regulation of CD8 responses, the regulation of antibody production by B cells and the regulation of cell recruitment in inflammatory responses. Both CD4⁺ and CD8⁺ T cells develop most efficiently in the thymus via a complex differentiation programme, and so resistance to viral and other pathogens is compromised in conditions where the thymus fails to develop or function correctly, such as in diGeorge syndrome in humans and in nude rodents. ³ Thus, an analysis of the regulatory processes during intrathymic T-cell development is critical for understanding the complexity of cellular and molecular interactions that constitute the immune response.

Intrathymic maturation is initiated when haemopoietic precursors are recruited to the thymus from sites such as yolk sac, fetal liver or bone marrow via a chemokine-mediated mechanism.^4,5 After thymic entry, precursors are triggered by the surrounding thymic microenvironment to undergo a series of differentiation steps, which include rearrangement and expression of genes encoding the β-chain of the TCR complex. Cells bearing productively rearranged TCR-β proteins are able to express a complete pre-TCR complex, signalling through which then triggers further maturational events, including cessation of TCR-β rearrangement, induction of TCR-α rearrangement and expression of CD4 and CD8 co-receptors. ^6–8 Such differentiation events are also accompanied by an extensive wave of cellular proliferation, which ultimately gives rise to a large pool of non-dividing CD4⁺ CD8⁺ thymocytes bearing low levels of the αβTCR complex (CD4⁺ CD8⁺ αβTCR^low cells).

As the random gene rearrangement processes regulating αβTCR expression generate a diverse repertoire of TCR specificities, it is essential that CD4⁺ CD8⁺ thymocytes undergo stringent selection events, which eliminate the risk of autoreactivity and at the same time promote the maturation of cells capable of participating in an immune response. Thus, lack of TCR ligation by self-MHC molecules during the 3–4 day lifespan of CD4⁺ CD8⁺ thymocytes results in the induction of a death-by-neglect mechanism, ⁹ while signals through the TCR can result in two distinct developmental fates: induction of apoptosis (negative selection) or induction of differentiation (positive selection). Precisely how both developmental outcomes can be achieved as a result of αβTCR–peptide/MHC interactions at the CD4⁺ CD8⁺ stage of thymocyte development is a major paradox in the intrathymic development of T cells. ^10–12

A number of experimental systems have been employed to study both the molecular and cellular mechanisms regulating intrathymic positive- and negative-selection events. In recent years, an approach that has been extensively used to study several aspects of thymocyte maturation is fetal thymus organ culture (FTOC). This approach, in which isolated embryonic thymus lobes are explanted in vitro, allows investigators to access and manipulate aspects of development, including thymic selection, which would be difficult to study in vivo. ¹³ For example, FTOC analyses have been essential in understanding the role of MHC-bound peptides in positive and negative selection. ¹⁴ Moreover, study of thymic stromal cell regulation of positive- and negative-selection events has recently been made possible in vitro by the establishment of reaggregation thymus organ culture (RTOC) techniques ( Fig. 1) allowing reassociation of defined thymocyte and stromal cell combinations. ^15–18 The primary aim of this review is to summarize current knowledge of the regulatory mechanisms of T-cell selection in the thymus, and to highlight the use of organ culture techniques in these studies.

Stage-specific analysis of T-cell development in reaggregate thymus organ culture (RTOC). In conventional fetal thymus organ culture (FTOC), thymus lobes isolated from embryos of 15 days' gestation are cultured for a number of days. At the outset of culture, all thymocytes are of the CD4^– CD8^– phenotype, but within a 5-day culture period, as shown, cells progress through to the CD4⁺ CD8⁺ stage of development. In contrast, RTOCs can be initiated with the desired thymocyte subset, in this case CD4⁺ CD8⁺ thymocytes, and their development analysed in the presence of defined thymic stromal cells. In this manner, thymic selection events can be analysed in RTOC separately from other thymic events, which occur in conventional FTOC, such as maturation from the CD4^– CD8^– to CD4⁺ CD8⁺ stage. FACS, fluorescence-activated cell sorter; 2-Guo, 2-deoxyguanosine.

SPECIALIZATION OF THE THYMIC MICROENVIRONMENT FOR POSITIVE and NEGATIVE SELECTION

The thymic microenvironment is a complexity of stromal cell types including cortical and medullary epithelial cells, macrophages, dendritic cells and mesenchymal fibroblasts. ¹⁹ Accumulating evidence suggests that each of these cell types play an important role during thymocyte development by providing signals that lead to differentiation, proliferation, or cell death. ²⁰ With respect to T-cell selection events, pioneering experiments involving bone marrow chimaeras showed that the process of MHC restriction (positive selection) requires MHC presentation by radioresistant thymic stromal cells (reviewed in ref. 21). Since then, many other studies utilizing FTOC methodology have examined the role of thymic stromal cells in the maturation of CD4⁺ CD8⁺ thymocytes. These are summarized below.

Stromal cell requirements for positive selection

Unlike most epithelia, the epithelial cells in the cortex of the thymus express both MHC class I and class II antigens, ²² which provides them with the ability to promote positive selection of both CD8⁺ and CD4⁺ T cells. Indeed, a number of FTOC-based studies have highlighted the importance of thymic epithelial cells in the positive-selection process. Thus, alymphoid embryonic thymus lobes, consisting mainly of MHC class II⁺ epithelial cells, support the generation of mature CD4⁺ and CD8⁺ T cells when recolonized by lymphoid precursors in vivo²³ and in vitro. ²⁴ However, although it is clear that thymic epithelial cells can support positive selection, it is still controversial as to whether this ability is a unique property of thymic epithelium, or one which is shared by other cell types. Indeed, several studies indicate that the requirement for provision of TCR ligands during positive selection, in the shape of peptide/MHC complexes, can be provided by a wide variety of cells including haemopoietic cells and fibroblasts. ^25–27 However, FTOC experiments in which CD4⁺ CD8⁺ thymocytes are reassociated with defined stromal cell types (for example non-thymic epithelia, dendritic cells) in the absence of thymic epithelial-cell support, provide strong evidence that thymic epithelial cells are uniquely efficient in their ability to drive maturation to the CD4⁺ and CD8⁺ stages. ²⁸

Importantly, these studies highlight the fact that the induction of positive selection is dependent upon costimulatory signals in addition to those generated by TCR ligation, which appear to be provided specifically by thymic epithelial cells. The nature of the accessory signals involved in the process of positive selection are unknown. However, recent evidence suggests that there is a specific need for thymic epithelial cells during the induction of differentiation, rather than thymic epithelium merely providing survival signals to reveal some intrinsic differentiation event within CD4⁺ CD8⁺ TCR^low thymocytes themselves. ²⁹ Thus, maturation of CD4⁺ CD8⁺ thymocytes whose in vitro lifespan has been extended as a consequence of expression of a bcl-2 transgene is still strictly dependent upon the presence of MHC class II⁺ thymic epithelial cells, and does not occur when they are reassociated with non-thymic stromal cells. ²⁹

While the signals derived from thymic epithelial cells (which drive differentiation of CD4⁺ CD8⁺ thymocytes) is poorly understood, Ashwell et al. have proposed that steroid production by thymic epithelial cells may play a role in the positive-selection process by antagonizing TCR-driven signals that would otherwise result in the induction of apoptosis. Thus, pharmacological inhibition of glucocorticoid (GC) receptor signalling results in an increase in antigen-specific deletion, ³⁰ while inhibiting GC production in FTOC causes thymocytes, which would normally undergo positive selection, to be triggered into apoptosis. ³¹ Such observations are strengthened by the detection of the key steroidogenic enzyme, p450scc, in cells present in the thymus. ³⁰ Recently, however, we have shown that MHC class II⁺ thymic epithelial cells isolated from 2-deoxyguanosine (2-Guo)-treated embryonic thymus lobes, which efficiently support positive selection in RTOC, ^16–18 do not express the p450scc enzyme. ³² However, perhaps surprisingly, p450scc mRNA was detected in thymocytes undergoing positive-selection events. ³² Thus, while these data do not rule out the possibility that steroid production plays a role in thymic-selection events, they argue against the notion that the specialization of thymic cortical epithelial cells for positive selection is critically dependent upon steroid biosynthesis.

Stromal cell requirements for negative selection

As well as demonstrating the importance of epithelial cells in intrathymic positive selection, several studies have analysed the stromal cell requirements for negative selection of CD4⁺ CD8⁺ thymocytes, which collectively suggest that there is also a degree of stromal cell specialization in this process. For example, using an MHC class II-restricted TCR transgenic (tg) RTOC-based system, Volkmann et al. ³³ showed that a combination of thymic dendritic cells and antigenic peptide (in this case C5) resulted in effective deletion of CD4⁺ CD8⁺ thymocytes. Such observations on the effectiveness of dendritic cells for negative selection in RTOC agrees with previous studies of Jenkinson et al., ¹⁸ using the Vβ8-reactive superantigen, Staphycoccal enterotoxin B (SEB), and an FTOC microinjection system based on Mls1a-mediated deletion of Vβ6⁺ thymocytes, described by Mazda et al. ³⁴

While it is clear from these FTOC-based studies that dendritic cells are effective mediators of negative selection, there is considerable controversy regarding the efficiency by which negative selection can be mediated by other cell types. Thus, both cortical and medullary cells appear to be capable of mediating negative selection in the C5 TCRtg system, ³³ but in another study SEB presentation by thymic epithelial cells was unable to mediate deletion of CD4⁺ CD8⁺ Vβ8⁺ thymocytes. ¹⁸ Collectively then, these data suggest that under certain circumstances, perhaps particularly in the case of TCRtg mice expressing higher than normal levels of TCR resulting in high-avidity TCR–MHC interactions, a variety of cell types can mediate negative selection. However, for deletion of non-TCRtg CD4⁺ CD8⁺ thymocytes bearing low levels of αβTCR, a hierarchy may exist in relation to the ability of stromal cells to mediate negative selection, with dendritic cells being the most efficient. Indeed, further evidence for the specialization of dendritic cells in mediating negative selection comes from experiments in which small numbers of dendritic cells were titrated into RTOCs of epithelial cells and CD4⁺ CD8⁺ thymocytes. ³⁵ In this study, the introduction of 1% dendritic cells – as a proportion of total thymus cellularity – was found to induce a maximal effect on the generation of CD4⁺ and CD8⁺ cells, with numbers being reduced by up to 75%, indicating that very few dendritic cells can have a potent effect on the outcome of thymic-selection events.

Collectively, these data suggest that the most efficient mediators of positive selection are thymic epithelial cells, while the most efficient mediators of negative selection are dendritic cells. The accessory molecules which are expressed by epithelial cells and dendritic cells and responsible for this specialization are not clear. However, several candidates such as CD80/CD86–CD28, ³⁶ CD30-CD30L ³⁷ and CD40-CD40L ³⁸ have been suggested to play a role in negative selection in some cases. In contrast, data on the molecular interactions mediating positive selection is scarce, and so identification of the costimulatory molecules expressed by thymic epithelial cells remains an important area for study.

THE ROLE OF MHC-BOUND PEPTIDES IN POSITIVE and NEGATIVE SELECTION

As outlined above, although positive and negative selection share a common requirement for signalling through the αβTCR, it seems probable that the developmental outcome of such signalling is regulated by a number of events, such as the avidity of TCR–MHC interactions, duration of TCR ligation and differential activation of intracellular signalling pathways. ³⁹ All of these parameters may depend on the nature of the αβTCR ligand for positive and negative selection, namely MHC molecules loaded with peptides derived from self-proteins. Experiments using FTOC have provided important information on the involvement of MHC-bound peptides in the discrimination between positive selection. Recent examples of such studies are summarized below.

Peptide specificity in positive and negative selection

FTOC experiments performed in the laboratories of Bevan^40,41 and Tonegawa^42,43 provided conclusive evidence that MHC class I-bound peptides play a direct role in influencing the developmental choice between positive and negative selection. However, while both groups showed that addition of exogenous peptides to either β₂-microglobulin-deficient (β₂m^–/–) or transporter-associated protein 1-deficient (TAP-1^–/–) FTOCs resulted in the rescue of positive selection of CD4^– CD8⁺ cells, conflicting evidence was produced regarding the precise role of MHC-bound peptides in this process. Thus, Hogquist et al. provided evidence of a specific requirement for antagonist peptides in mediating positive selection,^40,41 while Ashton-Rickardt et al. proposed an avidity-based model of T-cell selection, in which the developmental outcome of TCR ligation is dependent upon the number of TCRs engaged by peptide/MHC complexes. ^42–44 Importantly, however, a number of studies have now shown that although low concentrations of MHC class I-bound agonist peptides can mediate phenotypic changes reminiscent of positive selection, this is not accompanied by the generation of functional T cells, which can be activated by the positively selecting peptide.^45,46 In contrast, however, the generation of functional CD4⁺ T cells reactive to the same positively selecting MHC class II bound peptide has been observed. ⁴⁷ Thus, it may be the case that peptides bound to MHC molecules influence positive selection via different mechanisms depending upon the specificity of the TCR for MHC class I or class II, with a role for agonist peptides in CD4⁺-positive selection and antagonist peptides in CD8⁺-positive selection.

Impact of peptide diversity on T-cell selection events

While the above studies clearly demonstrate the importance of peptides in positive and negative selection, until recently relatively little was known about the nature of the endogenous self-peptides mediating T-cell selection, and how important the diversity of MHC-bound peptides is for generation of a broad repertoire of TCR specificities. However, further information on the nature of self-peptides in T-cell selection will probably be forthcoming, because two recent studies have isolated endogenous peptides from MHC class I molecules with the capacity to induce positive selection of CD8⁺ T cells in β₂m^–/– or TAP1^–/– FTOCs.^48,49

With regard to the role of peptide diversity, Rudensky and colleagues have provided important evidence that low-abundance, diverse peptides play a key role in the generation of a diverse T-cell repertoire.^50,51 Their studies utilize FTOCs from mice where the MHC class II-bound peptide repertoire is limited, for example in H-2M^–/– mice, where the dominant peptide is invariant chain-derived class II-associated invariant chain peptide (CLIP). Thus, Grubin et al. ⁵⁰ showed that blockade of positive selection induced by MHC class II/CLIP complexes in H-2M^–/– FTOC using the specific antibody 30-2 resulted in an increase in the positive selection of CD4⁺ T cells, suggesting that low abundance, possibly diverse, peptides play an important role in generating a diverse pool of CD4⁺ T cells. In addition, introduction of H-2M^–/– or wild-type dendritic cells into RTOCs of wild-type epithelial cells results in a 20% and 80% reduction, respectively, in the generation of CD4⁺ T cells. ³⁴ Collectively then, these findings not only demonstrate the importance of peptide diversity in the efficiency of positive and negative selection, but also highlight the considerable degree of overlap that exists between positive- and negative-selection events.

Sustained interactions during thymic positive selection

In initial in vivo bromodeoxyuridine (BrdU) pulse-chase experiments analysing thymocyte precursor-product kinetics, it was noted that the there was a 3–4 day lag period before BrdU, initially incorporated by CD4⁺ CD8⁺ precursors, was detectable in CD4⁺ and CD8⁺ thymocytes. ⁹ Since then, accumulating evidence has indicated that this lag phase represents the duration of the positive-selection process, and it has become clear that CD4⁺ CD8⁺ thymocytes undergoing positive selection transit through a number of intermediate stages before the generation of functionally mature CD4⁺ and CD8⁺ T cells. In an important initial study, Bendelac et al.⁵² demonstrated that induction of positive selection is accompanied by transient expression of CD69 within the CD4⁺ CD8⁺ thymocyte subset, an early-activation marker that is also expressed after TCR ligation on mature T cells, ⁵³ and that CD69 expression correlates with those cells which have up-regulated surface expression of the αβTCR complex. In addition, a number of studies subsequently showed that induction of CD69 expression during positive selection is dependent upon ligation of the αβTCR.^15,54^,⁵⁵ In addition to induction of CD69 expression, positive selection is also accompanied by up-regulation of CD5, ⁵⁶ gradual loss of CD4 in the generation of CD8⁺ T cells and gradual loss of CD8 in the generation of CD4⁺ T cells.^57,58 Thus, CD4⁺ CD8⁺ CD69⁺, CD4^lo CD8⁺ and CD4⁺ CD8^lo subsets of thymocytes represent developmental intermediates in the positive-selection process. ⁵⁹

Although the above studies indicate that positive selection of thymocytes is a multistage process, the interactions required for transition between these intermediate stages are poorly defined. However, a number of studies have now provided evidence that many of these intermediate events are still regulated by interactions with thymic stromal cells. ^60–62 For example, by comparing development of CD4⁺ CD8⁺ CD69^– thymocytes in RTOCs of wild-type and MHC-deficient (MHC^–/–) thymic stromal cells, it is clear that the induction phase of positive selection is critically dependent upon interactions between the TCR and peptide/MHC. In contrast, development of CD4⁺ CD8⁺ C69⁺ thymocytes resulting in the generation of functionally mature CD4⁺ and CD8⁺ cells occurs in the presence of either wild-type or MHC^–/– thymic stroma. ⁶⁰ Collectively, these data indicate that once the induction phase of positive selection has occurred, phenotypic and functional maturation to the CD4⁺ and CD8⁺ stages occurs independently of further TCR–MHC interactions. Importantly, however, interactions with thymic stromal cells still appear to be required for the completion of positive selection and acquisition of functional maturation because CD4⁺ and CD8⁺ cells generated from bcl-2tg CD4⁺ CD8⁺ CD69⁺ precursors in the absence of thymic stroma are unable to respond to TCR ligation by proliferation. Thus, following the generation of CD4⁺ CD8⁺ CD69⁺ intermediates as a result of TCR–MHC interactions with thymic stromal cells, the generation of functionally mature CD4⁺ and CD8⁺ cells is independent of further TCR signalling, but still dependent upon additional accessory interactions provided by thymic stroma.

Concluding remarks

In the past few years, experiments employing FTOC methodology have provided significant insights into the cellular and molecular mechanisms regulating several aspects of thymocyte-positive and -negative selection. In particular, FTOC and RTOC methodology have been pivotal in the identification of stromal-cell specialization for positive- and negative-selection events, and in understanding how MHC-bound peptides influence the development of CD4⁺ CD8⁺ thymocytes. Recent modifications of organ culture technology, such as systems allowing retroviral gene transfer,^63,64 strongly suggest that organ culture approaches will continue to be of considerable use in future studies on T-cell selection events.

References

1 Davis M.M., Boniface J.J., Reich Z. et al. (1998) Ligand recognition by alpha beta T cell receptors. Annu Rev Immunol 16, 523.
10.1146/annurev.immunol.16.1.523
CAS PubMed Web of Science® Google Scholar
2 Mazza G., Housset D., Piras C. et al. (1998) Glimpses at the recognition of peptide/MHC complexes by T-cell antigen receptors. Immunol Rev 163, 187.
10.1111/j.1600-065X.1998.tb01197.x
CAS PubMed Web of Science® Google Scholar
3 Conley M.E. (1995) Primary immunodeficiencies: a flurry of new genes. Immunol Today 16, 313.
10.1016/0167-5699(95)80142-1
CAS PubMed Web of Science® Google Scholar
4 Dunon D. & Imhof B.A. (1993) Mechanisms of thymus homing. Blood 81, 1.
CAS PubMed Web of Science® Google Scholar
5 Champion S., Imhof B.A., Savagner P., Thiery J.P. (1986) The embryonic thymus produces chemotactic peptides involved in the homing of hemopoietic precursors. Cell 44, 781.
10.1016/0092-8674(86)90844-5
CAS PubMed Web of Science® Google Scholar
6 Von Boehmer H., Aifantis I., Feinberg J. et al. (1999) Pleiotropic changes controlled by the pre-T-cell receptor. Curr Opin Immunol 11, 135.
10.1016/S0952-7915(99)80024-7
CAS PubMed Web of Science® Google Scholar
7 Buer J., Aifantis I., Disanto J.P., Fehling H.J., Von Boehmer H. (1997) Role of different T cell receptors in the development of pre-T cells. J Exp Med 185, 1541.
10.1084/jem.185.9.1541
CAS PubMed Web of Science® Google Scholar
8 Aifantis I., Buer J., Von Boehmer H., Azogui O. (1997) Essential role of the pre-T cell receptor in allelic exclusion of the T cell receptor beta locus. Immunity 199, 601.
10.1016/S1074-7613(00)80381-7
Web of Science® Google Scholar
9 Egerton M., Scollay R., Shortman K. (1990) Kinetics of mature T-cell development in the thymus. Proc Natl Acad Sci USA 87, 2579.
10.1073/pnas.87.7.2579
CAS PubMed Web of Science® Google Scholar
10 Benoist C. & Mathis D. (1997) Positive selection of T cells: fastidious or promiscuous? Curr Opin Immunol 9, 245.
10.1016/S0952-7915(97)80143-4
CAS PubMed Web of Science® Google Scholar
11 Teh H.S., Motyka B., Teh S.J. (1997) Influence of the affinity of selecting ligands on T cell positive and negative selection and the functional maturity of the positively selected T cells. Crit Rev Immunol 17, 399.
PubMed Web of Science® Google Scholar
12 Jameson S.C. & Bevan M.J. (1998) T-cell selection. Curr Opin Immunol 10, 214.
10.1016/S0952-7915(98)80251-3
CAS PubMed Web of Science® Google Scholar
13 Hare K.J., Jenkinson E.J., Anderson G. (1999) In vitro models of T cell development. Semin Immunol 11, 3.
10.1006/smim.1998.0151
CAS PubMed Web of Science® Google Scholar
14 Jenkinson E.J. & Anderson G. (1994) Fetal thymic organ cultures. Curr Opin Immunol 6, 293.
10.1016/0952-7915(94)90104-X
CAS PubMed Web of Science® Google Scholar
15 Anderson G., Owen J.J., Moore N.C., Jenkinson E.J. (1994) Characteristics of an in vitro system of thymocyte positive selection. J Immunol 153, 1915.
10.4049/jimmunol.153.5.1915
CAS PubMed Web of Science® Google Scholar
16 Anderson G., Jenkinson E.J., Moore N.C., Owen J.J.T. (1993) MHC class II-positive epithelium and mesenchyme cells are both required for T-cell development in the thymus. Nature 362, 70.
10.1038/362070a0
CAS PubMed Web of Science® Google Scholar
17 Jenkinson E.J., Anderson G., Moore N.C., Smith C.A., Owen J.J.T. (1994) Positive selection by purified MHC class II⁺ thymic epithelial cells in vitro: costimulatory signals mediated by B7 are not involved . Dev Immunol 3, 265.
10.1155/1994/75434
CAS PubMed Web of Science® Google Scholar
18 Jenkinson E.J., Anderson G., Owen J.J.T. (1992) Studies on T cell maturation on defined thymic stromal cell populations in vitro. J Exp Med 176, 845.
10.1084/jem.176.3.845
CAS PubMed Web of Science® Google Scholar
19 Boyd R.L., Tucek C.L., Godfrey D.I. et al. (1993) The thymic microenvironment. Immunol Today 14, 445.
10.1016/0167-5699(93)90248-J
CAS PubMed Web of Science® Google Scholar
20 Anderson G., Moore N.C., Owen J.J.T., Jenkinson E.J. (1996) Cellular interactions in thymocyte development. Annu Rev Immunol 14, 73.
10.1146/annurev.immunol.14.1.73
CAS PubMed Web of Science® Google Scholar
21 Zinkernagel R.M. & Doherty P.C. (1997) The discovery of MHC restriction. Immunol Today 18, 14.
10.1016/S0167-5699(97)80008-4
CAS PubMed Web of Science® Google Scholar
22 Rouse R.V. & Weissman I.L. (1982) The principal cells in the thymus expressing MHC antigens are epithelial. Adv Exp Med Biol 149, 401.
10.1007/978-1-4684-9066-4_55
PubMed Web of Science® Google Scholar
23 Ready A.R., Jenkinson E.J., Kingston R., Owen J.J.T. (1984) Successful transplantation across major histocompatibility barrier of deoxyguanosine-treated embryonic thymus expressing class II antigens. Nature 310, 231.
10.1038/310231a0
CAS PubMed Web of Science® Google Scholar
24 Kingston R., Jenkinson E.J., Owen J.J.T. (1985) A single stem cell can recolonize an embryonic thymus, producing phenotypically distinct T-cell populations. Nature 317, 811.
10.1038/317811a0
CAS PubMed Web of Science® Google Scholar
25 Bix M. & Raulet D. (1992) Inefficient positive selection of T cells directed by haematopoietic cells. Nature 359, 330.
10.1038/359330a0
CAS PubMed Web of Science® Google Scholar
26 Hugo P., Kappler J.W., McCormack J.E., Marrack P. (1993) Fibroblasts can induce thymocyte positive selection in vivo. Proc Natl Acad Sci USA 90, 10335.
10.1073/pnas.90.21.10335
CAS PubMed Web of Science® Google Scholar
27 Pawlowski T., Elliott J.D., Loh D.Y., Staerz U.D. (1993) Positive selection of T lymphocytes on fibroblasts. Nature 364, 642.
10.1038/364642a0
CAS PubMed Web of Science® Google Scholar
28 Anderson G., Owen J.J., Moore N.C., Jenkinson E.J. (1994) Thymic epithelial cells provide unique signals for positive selection of CD4⁺ CD8⁺ thymocytes in vitro. J Exp Med 179, 2027.
10.1084/jem.179.6.2027
CAS PubMed Web of Science® Google Scholar
29 Anderson G., Hare K.J., Platt N., Jenkinson E.J. (1997) Discrimination between maintenance- and differentiation-inducing signals during initial and intermediate stages of positive selection. Eur J Immunol 27, 1838.
10.1002/eji.1830270803
CAS PubMed Web of Science® Google Scholar
30 Vacchio M.S., Papadopoulos V., Ashwell J.D. (1994) Steroid production in the thymus: implications for thymocyte selection. J Exp Med 179, 1835.
10.1084/jem.179.6.1835
CAS PubMed Web of Science® Google Scholar
31 Vacchio M.S. & Ashwell J.D. (1997) Thymus-derived glucocorticoids regulate antigen-specific positive selection. J Exp Med 185, 2033.
10.1084/jem.185.11.2033
CAS PubMed Web of Science® Google Scholar
32 Jenkinson E.J., Parnell S., Shuttleworth J., Owen J.J., Anderson G. (1999) Specialized ability of thymic epithelial cells to mediate positive selection does not require expression of the steroidogenic enzyme p450scc. J Immunol 163, 5781.
CAS PubMed Web of Science® Google Scholar
33 Volkmann A., Zal T., Stockinger B. (1997) Antigen-presenting cells in the thymus that can negatively select MHC class II-restricted T cells recognizing a circulating self antigen. J Immunol 158, 693.
CAS PubMed Web of Science® Google Scholar
34 Mazda O., Watanabe Y., Gyotoku J., Katsura Y. (1991) Requirement of dendritic cells and B cells in the clonal deletion of Mls-reactive T cells in the thymus. J Exp Med 173, 539.
10.1084/jem.173.3.539
CAS PubMed Web of Science® Google Scholar
35 Anderson G., Partington K.M., Jenkinson E.J. (1998) Differential effects of peptide diversity and stromal cell type in positive and negative selection in the thymus. J Immunol 161, 6599.
CAS PubMed Web of Science® Google Scholar
36 Amsen D. & Kruisbeek A.M. (1996) CD28–B7 interactions function to co-stimulate clonal deletion of double-positive thymocytes. Int Immunol 8, 1927.
10.1093/intimm/8.12.1927
CAS PubMed Web of Science® Google Scholar
37 Amakawa R., Hakem A., Kundig T.M. et al. (1996) Impaired negative selection of T cells in Hodgkin's disease antigen CD30-deficient mice. Cell 84, 551.
10.1016/S0092-8674(00)81031-4
CAS PubMed Web of Science® Google Scholar
38 Foy T.M., Page D.M., Waldschmidt T.J. et al. (1995) An essential role for gp39, the ligand for CD40, in thymic selection. J Exp Med 182, 1377.
10.1084/jem.182.5.1377
CAS PubMed Web of Science® Google Scholar
39 Amsen D. & Kruisbeek A.M. (1998) Thymocyte selection: not by TCR alone. Immunol Rev 165, 209.
10.1111/j.1600-065X.1998.tb01241.x
CAS PubMed Web of Science® Google Scholar
40 Hogquist K.A., Gavin M.A., Bevan M.J. (1993) Positive selection of CD8⁺ T cells induced by major histocompatibility complex binding peptides in fetal thymic organ culture. J Exp Med 177, 1469.
10.1084/jem.177.5.1469
CAS PubMed Web of Science® Google Scholar
41 Hogquist K.A., Jameson S.C., Heath W.R., Howard J.L., Bevan M.J., Carbone F.R. (1994) T cell receptor antagonist peptides induce positive selection. Cell 76, 17.
10.1016/0092-8674(94)90169-4
CAS PubMed Web of Science® Google Scholar
42 Ashton-Rickardt P.G., Van Kaer L., Schumacher T.N., Ploegh H.L., Tonegawa S. (1993) Peptide contributes to the specificity of positive selection of CD8⁺ T cells in the thymus. Cell 73, 1041.
10.1016/0092-8674(93)90281-T
CAS PubMed Web of Science® Google Scholar
43 Ashton-Rickardt P.G., Bandeira A., Delaney J.R. et al. (1994) Evidence for a differential avidity model of T cell selection in the thymus. Cell 76, 651.
10.1016/0092-8674(94)90505-3
CAS PubMed Web of Science® Google Scholar
44 Ashton-Rickardt P.G. & Tonegawa S. (1994) A differential-avidity model for T-cell selection. Immunol Today 15, 362.
10.1016/0167-5699(94)90174-0
CAS PubMed Web of Science® Google Scholar
45 Hogquist K.A., Jameson S.C., Bevan M.J. (1995) Strong agonist ligands for the T cell receptor do not mediate positive selection of functional CD8⁺ T cells. Immunity 3, 79.
10.1016/1074-7613(95)90160-4
CAS PubMed Web of Science® Google Scholar
46 Sebzda E., Kundig T.M., Thomson C.T. et al. (1996) Mature T cell reactivity altered by peptide agonist that induces positive selection. J Exp Med 183, 1093.
10.1084/jem.183.3.1093
CAS PubMed Web of Science® Google Scholar
47 Nakano N., Rooke R., Benoist C., Mathis D. (1997) Positive selection of T cells induced by viral delivery of neopeptides to the thymus. Science 275, 678.
10.1126/science.275.5300.678
CAS PubMed Web of Science® Google Scholar
48 Hogquist K.A., Tomlinson A.J., Kieper W.C. et al. (1997) Identification of a naturally occurring ligand for thymic positive selection. Immunity 6, 389.
10.1016/S1074-7613(00)80282-4
CAS PubMed Web of Science® Google Scholar
49 Hu Q., Bazemore Walker C.R., Girao C. et al. (1997) Specific recognition of thymic self-peptides induces the positive selection of cytotoxic T lymphocytes. Immunity 7, 221.
10.1016/S1074-7613(00)80525-7
CAS PubMed Web of Science® Google Scholar
50 Grubin C.E., Kovats S., DeRoos P., Rudensky A.Y. (1997) Deficient positive selection of CD4 T cells in mice displaying altered repertoires of MHC class II-bound self-peptides. Immunity 7, 197.
10.1016/S1074-7613(00)80523-3
CAS PubMed Web of Science® Google Scholar
51 Barton G.M. & Rudensky A.Y. (1999) Requirement for diverse, low-abundance peptides in positive selection of T cells. Science 283, 67.
10.1126/science.283.5398.67
CAS PubMed Web of Science® Google Scholar
52 Bendelac A., Matzinger P., Seder R.A., Paul W.E., Schwartz R.H. (1992) Activation events during thymic selection. J Exp Med 175, 731.
10.1084/jem.175.3.731
CAS PubMed Web of Science® Google Scholar
53 Ziegler S.F., Ramsdell F., Alderson M.R. (1994) The activation antigen CD69. Stem Cells 12, 456.
10.1002/stem.5530120502
CAS PubMed Web of Science® Google Scholar
54 Yamashita I., Nagata T., Tada T., Nakayama T. (1993) CD69 cell surface expression identifies developing thymocytes which audition for T cell antigen receptor-mediated positive selection. Int Immunol 5, 1139.
10.1093/intimm/5.9.1139
CAS PubMed Web of Science® Google Scholar
55 Swat W., Dessing M., Von Boehmer H., Kisielow P. (1993) CD69 expression during selection and maturation of CD4⁺8⁺ thymocytes. Eur J Immunol 23, 739.
10.1002/eji.1830230326
CAS PubMed Web of Science® Google Scholar
56 Merkenschlager M., Graf D., Lovatt M., Bommhardt U., Zamoyska R., Fisher A.G. (1997) How many thymocytes audition for selection? J Exp Med 186, 1149.
10.1084/jem.186.7.1149
CAS PubMed Web of Science® Google Scholar
57 Lundberg K., Heath W., Kontgen F., Carbone F.R., Shortman K. (1995) Intermediate steps in positive selection: differentiation of CD4⁺8^int TCR^int thymocytes into CD4⁺TCR^hi thymocytes. J Exp Med 181, 1643.
10.1084/jem.181.5.1643
CAS PubMed Web of Science® Google Scholar
58 Kydd R., Lundberg K., Vremec D., Harris A.W., Shortman K. (1995) Intermediate steps in thymic positive selection. Generation of CD4⁺ T cells in culture from CD4⁺8⁺, CD4^int8⁺, and CD4⁺8^int thymocytes with up-regulated levels of TCR-CD3. J Immunol 155, 3806.
CAS PubMed Web of Science® Google Scholar
59 Anderson G., Hare K.J., Jenkinson E.J. (1999) Positive selection of thymocytes: the long and winding road. Immunol Today 20, 463.
10.1016/S0167-5699(99)01524-8
CAS PubMed Web of Science® Google Scholar
60 Hare K.J., Jenkinson E.J., Anderson G. (1999) CD69 expression discriminates MHC-dependent and -independent stages of thymocyte positive selection. J Immunol 162, 3978.
CAS PubMed Web of Science® Google Scholar
61 Wilkinson R.W., Anderson G., Owen J.J., Jenkinson E.J. (1995) Positive selection of thymocytes involves sustained interactions with the thymic microenvironment. J Immunol 155, 5234.
CAS PubMed Web of Science® Google Scholar
62 Dyall R. & Nikolic-Zugic J. (1995) The majority of postselection CD4⁺ single-positive thymocytes requires the thymus to produce long-lived, functional T cells. J Exp Med 181, 235.
10.1084/jem.181.1.235
CAS PubMed Web of Science® Google Scholar
63 Crompton T., Gilmour K.C., Owen M.J. (1996) The MAP kinase pathway controls differentiation from double-negative to double-positive thymocyte. Cell 86, 243.
10.1016/S0092-8674(00)80096-3
CAS PubMed Web of Science® Google Scholar
64 Sugawara T., Di Bartolo V., Miyazaki T., Nakauchi H., Acuto O., Takahama Y. (1998) An improved retroviral gene transfer technique demonstrates inhibition of CD4^– CD8^– thymocyte development by kinase-inactive ZAP-70. J Immunol 161, 2888.
CAS PubMed Web of Science® Google Scholar

Citing Literature

Volume100, Issue4

August 2000

Pages 405-410

Thymus organ cultures and T-cell receptor repertoire development

Introduction

SPECIALIZATION OF THE THYMIC MICROENVIRONMENT FOR POSITIVE and NEGATIVE SELECTION

Stromal cell requirements for positive selection

Stromal cell requirements for negative selection

THE ROLE OF MHC-BOUND PEPTIDES IN POSITIVE and NEGATIVE SELECTION

Peptide specificity in positive and negative selection

Impact of peptide diversity on T-cell selection events

Sustained interactions during thymic positive selection

Concluding remarks

References

Citing Literature

Figures

References

Information

About Wiley Online Library

Help & Support

Opportunities

Connect with Wiley

Thymus organ cultures and T-cell receptor repertoire development

Introduction

SPECIALIZATION OF THE THYMIC MICROENVIRONMENT FOR POSITIVE and NEGATIVE SELECTION

Stromal cell requirements for positive selection

Stromal cell requirements for negative selection

THE ROLE OF MHC-BOUND PEPTIDES IN POSITIVE and NEGATIVE SELECTION

Peptide specificity in positive and negative selection

Impact of peptide diversity on T-cell selection events

Sustained interactions during thymic positive selection

Concluding remarks

References

Citing Literature

Figures

References

Related

Information