Requirement of CD3 Complex-associated Signaling Functions for Expression of Rearranged T Cell Receptor VDJ Genes in Early Thymic Development (original) (raw)
Related papers
Proceedings of the National Academy of Sciences, 1999
During ␣ thymocyte development, clonotype-independent CD3 complexes are expressed at the cell surface before the pre-T cell receptor (TCR). Signaling through clonotype-independent CD3 complexes is required for expression of rearranged TCR genes. On expression of a TCR polypeptide chain, the pre-TCR is assembled, and TCR locus allelic exclusion is established. We investigated the putative contribution of clonotype-independent CD3 complex signaling to TCR locus allelic exclusion in mice singledeficient or double-deficient for CD3͞ and͞or p56 lck . These mice display defects in the expression of endogenous TCR genes in immature thymocytes, proportional to the severity of CD3 complex malfunction. Exclusion of endogenous TCR VDJ (variable, diversity, joining) rearrangements by a functional TCR transgene was severely compromised in the single-deficient and double-deficient mutant mice. In contrast to wild-type mice, most of the CD25 ؉ double-negative (DN) thymocytes of the mutant mice failed to express the TCR transgene, suggesting defective expression of the TCR transgene similar to endogenous TCR genes. In the mutant mice, a proportion of CD25 ؉ DN thymocytes that failed to express the transgene expressed endogenous TCR polypeptide chains. Many double-positive cells of the mutant mice coexpressed endogenous and transgenic TCR chains or more than one endogenous TCR chain. The data suggest that signaling through clonotype-independent CD3 complexes may contribute to allelic exclusion of the TCR locus by inducing the expression of rearranged TCR genes in CD25 ؉ DN thymocytes.
TCRA Gene Rearrangement in Immature Thymocytes in Absence of CD3, Pre-TCR, and TCR Signaling
The Journal of Immunology, 2001
During thymocyte differentiation, TCRA genes are massively rearranged only after productively rearranged TCRB genes are expressed in association with pT␣ and CD3 complex molecules within a pre-TCR. Signaling from the pre-TCR via the CD3 complex is thought to be required to promote TCRA gene accessibility and recombination. However, ␣ ؉ thymocytes do develop in pT␣-deficient mice, showing that TCR␣-chain genes are rearranged, either in CD4 ؊ CD8 ؊ or CD4 ؉ CD8 ؉ thymocytes, in the absence of pre-TCR expression. In this study, we analyzed the TCRA gene recombination status of early immature thymocytes in mutant mice with arrested thymocyte development, deficient for either CD3 or pT␣ and ␥c expression. ADV genes belonging to different families were found rearranged to multiple AJ segments in both cases. Thus, TCRA gene rearrangement is independent of CD3 and ␥c signaling. However, CD3 expression was found to play a role in transcription of rearranged TCR␣-chain genes in CD4 ؊ CD8 ؊ thymocytes. Taken together, these results provide new insights into the molecular control of early T cell differentiation.
Blood, 1999
Recent studies have identified several populations of progenitor cells in the human thymus. The hematopoietic precursor activity of these populations has been determined. The most primitive human thymocytes express high levels of CD34 and lack CD1a. These cells acquire CD1a and differentiate into CD4(+)CD8(+) through CD3(-)CD4(+)CD8(-) and CD3(-)CD4(+) CD8alpha+beta- intermediate populations. The status of gene rearrangements in the various TCR loci, in particular of TCRdelta and TCRgamma, has not been analyzed in detail. In the present study we have determined the status of TCR gene rearrangements of early human postnatal thymocyte subpopulations by Southern blot analysis. Our results indicate that TCRdelta rearrangements initiate in CD34(+)CD1a- cells preceding those in the TCRgamma and TCRbeta loci that commence in CD34(+)CD1a+ cells. Furthermore, we have examined at which cellular stage TCRbeta selection occurs in humans. We analyzed expression of cytoplasmic TCRbeta and cell-su...
Journal of Experimental Medicine, 1994
CD3 signal transducing proteins are thought to be expressed on the surface of T cells only as part of clonotypic T cell receptor (TCR) complexes. Contrary to this paradigm, the present study describes surface expression of CD3 proteins independently of clonotypic TCR complexes, but only on immature thymocytes. Such novel clonotype-independent CD3 (CIC) complexes are composed primarily of CD3 gamma epsilon and secondarily of CD3 delta epsilon heterodimers that are independent of one another and are expressed on the cell surface in association with an unknown 90-100 kD protein termed CD3-associated protein (CD3AP). CIC complexes are expressed in normal mice on early thymocytes through the CD4+CD8+ stage of development, but not on mature peripheral T cells. Furthermore, CIC complexes are expressed by both TCR- severe combined immunodeficiency (SCID) thymocytes and thymoma cell lines, in the absence of any clonotypic chains. The isolation and biochemical characterization of surface CIC ...
Essential and Partially Overlapping Role of CD3 and CD3 for Development of and T Lymphocytes
Journal of Experimental Medicine, 1998
CD3γ and CD3δ are two highly related components of the T cell receptor (TCR)–CD3 complex which is essential for the assembly and signal transduction of the T cell receptor on mature T cells. In gene knockout mice deficient in either CD3δ or CD3γ, early thymic development mediated by pre-TCR was either undisturbed or severely blocked, respectively, and small numbers of TCR-αβ+ T cells were detected in the periphery of both mice. γδ T cell development was either normal in CD3δ−/− mice or partially blocked in CD3γ−/− mice. To examine the collective role of CD3γ and CD3δ in the assembly and function of pre-TCR and in the development of γδ T cells, we generated a mouse strain with a disruption in both CD3γ and CD3δ genes (CD3γδ−/−). In contrast to mice deficient in either CD3γ or CD3δ chains, early thymic development mediated by pre-TCR is completely blocked, and TCR-αβ+ or TCR-γδ+ T cells were absent in the CD3γδ−/− mice. Taken together, these studies demonstrated that CD3γ and CD3δ pla...
Molecular mechanisms that control mouse and human TCR-αβ and TCR-γδ T cell development
Seminars in Immunopathology, 2008
Following specification of hematopoietic precursor cells into the T cell lineage, several developmental options remain available to the immature thymocytes. The paradigm is that the outcome of the T cell receptor rearrangements and the corresponding T cell receptor signaling events will be predominant to determine the first of these choices: the αβ versus γδ T cell pathways. Here, we review the thymus-derived environmental signals, the transcriptional mediators, and other molecular mechanisms that are also involved in this decision in both the mouse and human. We discuss the differences in cellular events between the αβ and γδ developmental pathways and try to correlate these with a corresponding complexity of the molecular mechanisms that support them.
The timing of TCR expression critically influences T cell development and selection
Journal of Experimental Medicine, 2005
Sequential rearrangement of the T cell receptor for antigen (TCR)  and ␣ chains is a hallmark of thymocyte development. This temporal control is lost in TCR transgenics because the ␣ chain is expressed prematurely at the CD4 ؊ CD8 ؊ double negative (DN) stage. To test the importance of this, we expressed the HY ␣ chain at the physiological CD4 ؉ CD8 ؉ double positive (DP) stage. The reduced DP and increased DN cellularity typically seen in TCR transgenics was not observed when the ␣ chain was expressed at the appropriate stage. Surprisingly, antigen-driven selection events were also altered. In male mice, thymocyte deletion now occurred at the single positive or medullary stage. In addition, no expansion of CD8 ␣␣ intestinal intraepithelial lymphocytes (IELs) was observed, despite the fact that HY transgenics have been used to model IEL development. Collectively, these data establish the importance of proper timing of TCR expression in thymic development and selection and emphasize the need to use models that most accurately reflect the physiologic process.
Constitutive expression of the pre-TCR enables development of mature T cells
International Immunology, 2006
Expression and signalling through the pre-TCR and the TCRab resemble two critical checkpoints during T cell development. We investigated to which extent a pre-TCR can functionally replace mature TCRa chains during T cell development. For this purpose, transgenic mice were generated expressing the pre-TCRa (pTa) under the transcriptional control of TCRb regulatory elements. We report here on the interesting finding that constitutive pTa expression allows complete T cell maturation. The pre-TCR complex permits a subset of b-selected thymocytes to mature in the absence of TCRa into peripheral T cells (bT cells) comprising up to 10% of all lymphocytes. Lymphopenia-driven proliferation of these bT cells is similar to that of conventional abT cells. Furthermore, bT cells proliferated and acquired effector function upon stimulation with allogeneic MHC.