Thymic output and HIV infection: on the right TREC.
ABSTRACT The role of the thymus in HIV infection has been a matter of considerable debate. A new study by Dion et al. (2004) in this issue of Immunity provides the mechanism for reduced thymic output in HIV infection while illuminating the impact of recent thymic emigrants on peripheral T cell homeostasis.
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ABSTRACT: Disease progression and response to antiretroviral therapy (ART) in HIV-infected children is different to that of adults. Immune reconstitution in adults is mainly from memory T-cells, whereas in children it occurs predominantly from the naive T-cell pool. It is unclear however what proportion of reconstituted CD4 T-cells comes from thymic export and homeostatic proliferation in the periphery. Thymic output is often estimated by measuring T-cell receptor excision circles and markers such as CD31 expressed on recent thymic emigrants but these are confounded by peripheral T-cell division and cannot in themselves be used as quantitative estimates of thymic output. To compare thymic output in HIV-infected children on ART, HIV-infected children not on ART and uninfected children of different ages. Combined T-cell receptor excision circle (TREC) and proliferation data are used with a recently described mathematical model to give explicit measures of thymic output. We found that age-adjusted thymic output is reduced in untreated children with HIV, which increases significantly with length of time on ART. Our results suggest that a highly active thymus in early childhood may contribute to better immune reconstitution if ART is initiated early in life.AIDS (London, England) 09/2013; 28(2). DOI:10.1097/QAD.0000000000000063 · 6.56 Impact Factor
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ABSTRACT: Current tumor immunotherapy approaches include the genetic modification of peripheral T cells to express tumor antigen-specific T-cell receptors (TCRs). The approach, tested in melanoma, has led to some limited success of tumor regression in patients. Yet, the intro-duction of exogenous TCRs into mature T cells entails an underlying risk; the generation of autoreactive clones due to potential TCR mispairing, and the lack of effec-tive negative selection, as these peripheral cells do not undergo thymic selection following introduction of the exogenous TCR. We have successfully generated MART-1–specific CD8 T cells from genetically modified human hematopoietic stem cells (hHSC) in a humanized mouse model. The advantages of this approach include a long-term source of antigen specific T cells and proper T-cell selection due to thymopoiesis following expression of the TCR. In this report, we examine the molecular pro-cesses occurring on endogenous TCR expression and demonstrate that this approach results in exclusive cell surface expression of the newly introduced TCR, and the exclusion of endogenous TCR cell surface expression. This suggests that this stem cell based approach can pro-vide a potentially safer approach for anticancer immuno-therapy due to the involvement of thymic selection.Molecular Therapy 03/2013; 21(5). DOI:10.1038/mt.2013.28 · 6.43 Impact Factor