Home  About us  Contact
 

Medullary Thymic Epithelial Cells (medullary + thymic_epithelial_cell)

Distribution by Scientific Domains
Medical Sciences100%

Selected Abstracts

Sequential phases in the development of Aire-expressing medullary thymic epithelial cells involve distinct cellular input

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2008
Andrea
Abstract Intrathymic deletion of immature thymocytes that express self-reactive TCR specificities is essential in the generation of self tolerance. Medullary thymic epithelial cells (mTEC) expressing the transcriptional regulator Aire play a key role in this process by regulating expression of tissue-restricted antigens to ensure tolerance to peripheral tissues. Here, we have analysed the cellular and molecular requirements for the initial appearance of Aire+ mTEC in the embryonic thymus, in addition to their persistence in the adult thymus. Analysis of thymic ontogeny shows that the emergence of embryonic Aire+ mTEC occurs prior to the appearance of mature thymocytes, and depends upon lymphoid tissue inducer cells expressing retinoic acid receptor-related orphan receptor,,. In the adult thymus, we show that Aire+ mTEC develop in the absence of thymocyte positive and negative selection and CD40 signalling, but are present at reduced frequency. Collectively these data support a model where the initial differentiation of Aire+ mTEC involves receptor activator of NF-,B (RANK)-RANKL interactions with lymphoid tissue inducer cells, with subsequent mTEC turnover and/or survival involving CD40-mediated signalling following interactions with mature CD4+ thymocytes that express CD40L. [source]

Onset of promiscuous gene expression in murine fetal thymus organ culture

IMMUNOLOGY, Issue 3 2006
Renato Sousa Cardoso
Summary T-cell differentiation and induction of tolerance to self-antigens occurs mainly in the thymus. Thymic stromal cells, specifically medullary thymic epithelial cells, express a diverse set of genes encoding parenchymal organ-specific proteins. This phenomenon has been termed promiscuous gene expression (PGE) and has been implicated in preventing organ-specific autoimmunity by inducing T-cell tolerance to self antigens. Early thymopoiesis and the critical factors involved in T-cell differentiation can be reproduced in vitro by murine fetal thymus organ culture (FTOC), which mimics the natural thymic microenvironment. To evaluate the occurrence of PGE in FTOC, gene expression profiling during in vitro thymic development in BALB/c mice was performed using a set of nylon cDNA microarrays containing 9216 sequences. The statistical analysis of the microarray data (sam program) revealed the temporal repression and induction of 57 parenchymal and seven lymphoid organ-specific genes. Most of the genes analysed are repressed during early thymic development (15,17 days post-coitum). The expression of the autoimmune regulator (AIRE) gene at 16 days post-coitum marks the onset of PGE. This precedes the induction of parenchymal organ genes during the late developmental phase at 20 days post-coitum. The mechanism of T-cell tolerance induction begins during fetal development and continues into adulthood. Our findings are significant because they show a fine demarcation of PGE onset, which plays a central role in induction of T-cell tolerance. [source]

Autoimmune regulator controls T cell help for pathogenetic autoantibody production in collagen-induced arthritis

ARTHRITIS & RHEUMATISM, Issue 6 2009
Ian K. Campbell
Objective Autoimmune regulator (Aire) promotes the ectopic expression of tissue-restricted antigens in medullary thymic epithelial cells (mTECs), leading to negative selection of autoreactive T cells. This study was undertaken to determine whether loss of central tolerance renders Aire-deficient (Aire,/,) mice more susceptible to the induction of autoimmune arthritis. Methods Medullary TECs were isolated from Aire,/, and wild-type C57BL/6 mice for gene expression analysis. Collagen-induced arthritis (CIA) was elicited by injection of chick type II collagen (CII) in adjuvant. Cellular and humoral immune responses to CII were evaluated. Chimeric mice were created by reconstituting lymphocyte-deficient mice with either Aire,/, or wild-type CD4 T cells and wild-type B cells. Results Wild-type, but not Aire,/,, mTECs expressed the CII gene Col2a1. Aire,/, mice developed more rapid and severe CIA, showing elevated serum anti-CII IgG levels, with earlier switching to arthritogenic IgG subclasses. No evidence was found of enhanced T cell responsiveness to CII in Aire,/, mice; however, Aire,/, CD4 T cells were more efficient at stimulating wild-type B cells to produce anti-CII IgG following immunization of chimeric mice with CII. Conclusion Our findings indicate that Aire-dependent expression of CII occurs in mTECs, implying that there is central tolerance to self antigens found in articular cartilage. Reduced central tolerance to CII in Aire,/, mice manifests as increased CD4 T cell help to B cells for cross-reactive autoantibody production and enhanced CIA. Aire and central tolerance help prevent cross-reactive autoimmune responses to CII initiated by environmental stimuli and limit spontaneous autoimmunity. [source]