Triiodothyronine modulates differential homing of recent thymic emigrants to peripheral lymphoid organs

MM Ribeiro‐Carvalho, S Smaniotto… - Scandinavian …, 2007 - Wiley Online Library
MM Ribeiro‐Carvalho, S Smaniotto, S Neves‐dos‐Santos, T Mouço, W Savino
Scandinavian journal of immunology, 2007Wiley Online Library
The functioning of the immune system partially relies on T‐cell exportation from the thymus,
the major site of T‐cell differentiation. Although the molecular mechanisms governing this
process begin to be elucidated, it is not clear if thyroid hormones can alter the homing of
recent thymic emigrants (RTE) to peripheral lymphoid organs. Herein, we investigated
whether triiodothyronine (T3) could influence the homing of thymus‐derived T cells. For that
we used intrathymic injection of T3 in combination with fluorescein isothiocyanate (FITC) to …
Abstract
The functioning of the immune system partially relies on T‐cell exportation from the thymus, the major site of T‐cell differentiation. Although the molecular mechanisms governing this process begin to be elucidated, it is not clear if thyroid hormones can alter the homing of recent thymic emigrants (RTE) to peripheral lymphoid organs. Herein, we investigated whether triiodothyronine (T3) could influence the homing of thymus‐derived T cells. For that we used intrathymic injection of T3 in combination with fluorescein isothiocyanate (FITC) to trace, 16 h later, FITC+ cells, termed RTE, in peripheral lymphoid organs. We observed that T3 stimulated thymocyte export, increasing the frequency of CD4+ RTE and CD8+ RTE in the subcutaneous and mesenteric lymph nodes. By contrast, the relative numbers of CD4+ RTE in the spleen were decreased. T3 also changed the differential distribution pattern of CD4+ RTE, and to a lesser extent CD8+ RTE in the peripheral lymphoid organs. Moreover, the expression of extracellular matrix (ECM) components, such as laminin and fibronectin, which are known to be involved in T‐cell migration, increased in the lymph nodes but not in the spleen following intrathymic T3 treatment. In conclusion, our data correspond to the first demonstration that in vivo treatment with thyroid hormone stimulates thymic T‐cell homing and T‐cell distribution in peripheral lymphoid organs.
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