Establishment of human double-positive thymocyte clones.

Human thymocytes were sorted according to the expression of CD4 and CD8 molecules and clones representing the four subpopulations (DP, DN, and single CD4 or CD8 positive) were established. DP clones can be maintained for long periods in tissue culture and give rise to a variable percentage of SP variants. These variants, when isolated and further expanded, do not revert to a DP phenotype. DP clones express a functional TCR-CD3 complex, suggesting that this molecule can interact with the thymic microenvironment during T cell differentiation.

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Pre–T Cell Receptor (Tcr) and Tcr-Controlled Checkpoints in T Cell Differentiation Are Set by Ikaros

Journal of Experimental Medicine ◽

10.1084/jem.190.8.1039 ◽

1999 ◽

Vol 190 (8) ◽

pp. 1039-1048 ◽

Cited By ~ 108

Author(s):

Susan Winandy ◽

Li Wu ◽

Jin-Hong Wang ◽

Katia Georgopoulos

Keyword(s):

Cell Differentiation ◽

T Cell ◽

T Cell Receptor ◽

Cell Receptor ◽

T Cell Differentiation ◽

Tcr Signaling ◽

Double Positive ◽

Single Positive ◽

T Cell Malignancies ◽

Deficient Mice

T cell differentiation relies on pre–T cell receptor (TCR) and TCR signaling events that take place at successive steps of the pathway. Here, we show that two of these T cell differentiation checkpoints are regulated by Ikaros. In the absence of Ikaros, double negative thymocytes can differentiate to the double positive stage without expression of a pre-TCR complex. Subsequent events in T cell development mediated by TCR involving transition from the double positive to the single positive stage are also regulated by Ikaros. Nonetheless, in Ikaros-deficient thymocytes, the requirement of pre-TCR expression for expansion of immature thymocytes as they progress to the double positive stage is still maintained, and the T cell malignancies that invariably arise in the thymus of Ikaros-deficient mice are dependent on either pre-TCR or TCR signaling. We conclude that Ikaros regulates T cell differentiation, selection, and homeostasis by providing signaling thresholds for pre-TCR and TCR.

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Differential effects of γc cytokines on postselection differentiation of CD8 thymocytes

Blood ◽

10.1182/blood-2012-05-433508 ◽

2013 ◽

Vol 121 (1) ◽

pp. 107-117 ◽

Cited By ~ 21

Author(s):

Moutih Rafei ◽

Alexandre Rouette ◽

Sylvie Brochu ◽

Juan Ruiz Vanegas ◽

Claude Perreault

Keyword(s):

T Cells ◽

Cell Differentiation ◽

T Cell ◽

Positive Selection ◽

Cd8 T Cells ◽

Cd8 T Cell ◽

T Cell Differentiation ◽

Thymic Epithelial Cells ◽

Double Positive

Abstract The primary consequence of positive selection is to render thymocytes responsive to cytokines and chemokines expressed in the thymic medulla. In the present study, our main objective was to discover which cytokines could support the differentiation of positively selected thymocytes. To this end, we have developed an in vitro model suitable for high-throughput analyses of positive selection and CD8 T-cell differentiation. The model involves coculture of TCRhiCD5intCD69− double-positive (DP) thymocytes with peptide-pulsed OP9 cells and γc-cytokines. We report that IL-4, IL-7, and IL-21 have nonredundant effects on positively selected DP thymocytes. IL-7 signaling phosphorylates STAT5 and ERK; induces Foxo1, Klf2, and S1pr1; and supports the differentiation of classic CD8 T cells. IL-4 activates STAT6 and ERK and supports the differentiation of CD8intPD-L1hiCD44hiEOMES+ innate CD8 T cells. IL-21 is produced by thymic epithelial cells and the IL-21 receptor-α is strongly induced on DP thymocytes undergoing positive selection. IL-21 signaling phosphorylates STAT3 and STAT5, but not ERK, and does not support CD8 T-cell differentiation. However, IL-21 has a unique ability to up-regulate BCL-6, expand DP thymocytes undergoing positive selection, and increase the production of mature T cells. Our data suggest that injection of recombinant IL-21 might enhance thymic output in subjects with age- or disease-related thymic atrophy.

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Dysregulation of T-Cell Development in Adrenal Glucocorticoid-Deprived Rats

Experimental Biology and Medicine ◽

10.3181/0902-rm-63 ◽

2009 ◽

Vol 234 (9) ◽

pp. 1067-1074 ◽

Cited By ~ 9

Author(s):

Zorica Stojić-Vukanić ◽

Aleksandra Rauški ◽

Duško Kosec ◽

Katarina Radojević ◽

Ivan Pilipović ◽

...

Keyword(s):

Cell Differentiation ◽

T Cell ◽

T Cell Development ◽

Cell Development ◽

T Cell Differentiation ◽

Male Rats ◽

Double Positive ◽

Cell Repertoire ◽

Single Positive ◽

The Impact

A number of different experimental approaches have been used to elucidate the impact of basal levels of adrenal gland-derived glucocorticoids (GCs) on T cell development, and thereby T cell-mediated immune responses. However, the relevance of the adrenal GCs to T cell development is still far from clear. This study was undertaken to explore the relevance of basal levels of GCs to T cell differentiation/maturation. Eight days post-adrenalectomy in adult male rats the thymocyte yield, apoptotic and proliferative rate and the relationship amongst major thymocyte subsets, as defined by TCRαβ/CD4/CD8 expression, were examined using flow cytometry. Adrenal GC deprivation decreased thymocyte apoptosis and altered the kinetics of T cell differentiation/maturation. In the adrenalectomized rats there was increased thymic hypercellularity and an over-representation of the CD4+CD8+ double positive (DP) TCRαβlow cells entering selection, as well as increased numbers of their DP TCRαβ− immediate precursors. These changes were accompanied with under-representation of the postselected DP TCRαβhigh and the most mature CD4−CD8+ and, particularly, CD4+CD8− single positive (SP) TCRαβhigh cells. This data suggests that withdrawal of adrenal GCs produces alterations in the thymocyte selection processes, possibly affecting the diversity of functional T cell repertoire and generation of potentially self-reactive cells as indicated by the reduced proportion and number of CD4−CD8− double negative TCRαβhigh cells. In addition, it indicates that GCs influence the post-selection maturation of thymocytes and plays a regulatory role in controlling the ratio of mature CD4+CD8−/CD4−CD8+ SP TCRαβhigh cells.

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Lmo2 Induces T-Cell Leukemia with Epigenetic Deregulation of CD4.

Blood ◽

10.1182/blood.v112.11.3361.3361 ◽

2008 ◽

Vol 112 (11) ◽

pp. 3361-3361

Author(s):

Susan Cleveland ◽

Utpal P. Dave

Keyword(s):

Cell Differentiation ◽

T Cell ◽

Transgenic Mice ◽

Cell Line ◽

Trichostatin A ◽

T Cell Differentiation ◽

Transcriptional Level ◽

Double Negative ◽

Double Positive ◽

Single Positive

Abstract The LIM domain Only-2 (Lmo2) oncogene is deregulated in the majority of human T-cell acute lymphoblastic leukemias (T-ALL). Enforced, constitutive expression of Lmo2 in transgenic mice using the T-cell-specific Cd2 promoter/enhancer induces T-ALL with median latency of 200 days and 100% penetrance. These transgenic mice have a pre-leukemic differentiation block at the double negative stage (CD4− CD8−) of T-cell differentiation. Despite this, T-ALLs in these mice arise from various stages of T-cell differentiation. To explore the relationship between T-cell development and Lmo2 oncogene function, we established cell lines from four independent T-cell tumors representing the double negative (DN), double positive (DP), and single positive (SP) stages. Two of the lines showed variegated expression of CD4 antigen. One line, 32080, was striking in that CD4 was expressed in 50% of cells whereas CD8 was uniformly present. The cell line expressed markers consistent with the intermediate single positive stage (ISP) to double positive (DP) stage transition. We sorted the 32080 line for highly CD4 positive and negative cells and observed them in culture. After one week, both sorted populations showed variegated CD4 expression. We determined CD4 expression was regulated at the transcriptional level and not due to post-transcriptional effects and that cell replication was necessary to re-establish CD4 variegation. Importantly, variegated CD4 expression was dependent on Lmo2 because its knockdown resulted in decreased CD4 expression. HDAC inhibition by trichostatin A had the reciprocal effect of inducing more CD4 expression suggesting that chromatin modification was playing a role. The CD4 locus was analyzed by chromatin immunoprecipitation and histone H3 methylation patterns consistent with silencing were found in the CD4 negative sorted cells but not in the CD4 positive population. The 32080 cell line is a striking model of ISP to DP T-cell plasticity and invokes a novel mechanism by which Lmo2 functions.

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Electron microscope study of the secretory activity of epithelial cells in embryonic thymus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015945x ◽

1990 ◽

Vol 48 (3) ◽

pp. 382-383

Author(s):

H. Alasam

Keyword(s):

Cell Differentiation ◽

T Cell ◽

Epithelial Cells ◽

Electron Density ◽

Secretory Activity ◽

T Cell Differentiation ◽

High Electron ◽

Transmission Electron ◽

Medullary Epithelial Cells ◽

Thymic Factor

The possibility that intrathymic T-cell differentiation involves stem cell-lymphoid interactions in embryos led us to study the ultrastructure of epithelial cell in normal embryonic thymus. Studies in adult thymus showed that it produces several peptides that induce T-cell differentiation. Several of them have been chemically characterized, such as thymosin α 1, thymopoietin, thymic humoral factor or the serum thymic factor. It was suggested that most of these factors are secreted by populations of A and B-epithelial cells.Embryonic materials were obtained from inbred matings of Swiss Albino mice. Thymuses were disected from embryos 17 days old and prepared for transmission electron microscopy. Our studies showed that embryonic thymus at this stage contains undifferentiated and differentiated epithelial cells, large lymphoblasts, medium and few small lymphocytes (Fig. 5). No differences were found between cortical and medullary epithelial cells, in contrast to the findings of Van Vliet et al,. Epithelial cells were mostly of the A-type with low electron density in both cytoplasm and nucleus. However few B-type with high electron density were also found (Fig. 7).

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