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Developmental Immunology - Volume 7 2000, Issue 2-4, Pages 279-291



Laboratory on Thymus Research, Department of Immunology, Oswaldo Cruz Institute – Oswaldo Cruz Foundation, Rio de Janeiro, Brazil

Department of Biochemistry, Biology Institute, University of the State of Rio de Janeiro and Program of Experimental Medicine, Basic Research Center, National Cancer Institute, Rio de Janeiro, Brazil

Laboratory of Cell Biology, Department of Ultrastructure and Cell Biology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil

Laboratory on Thymus Research, Department of Immunology, Oswaldo Cruz Institute Oswaldo Cruz Foundation, Ave. Brasil 4365-Manguinhos - Rio de Janeiro 21045-900, Brazil



Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Cell adhesion, migration, differentiation and survival or death is amongst a large spectrum ofbiological responses that can be elicited by ligation of extracellular matrix components totheir corresponding receptors. As regards the physiology of the thymus, cell migration is acrucial event in the general process of T cell differentiation. Studies on the intrathymic distributionof ECM components revealed that fibronectin, laminin and type IV collagen, are notrestrictedly located at typical basement membrane sites, also forming a thick network in themedullary region of the thymic lobules, whereas very thin ECM fibers are found within thecortex. These ECM components are essentially produced by thymic microenvironmentalcells, which also drive thymocyte differentiation. Signals triggered by ECM are conveyedinto thymocytes or microenvironmental cells through specific membrane receptors, and mostof them belong to the integrin type, such as the VLA-3, VLA-4, VLA-5 and VLA-6. In vitrostudies revealed that adhesion of thymocytes to thymic microenvironmental cells is mediatedby extracellular matrix. Such an adhesion is preferentially done by immature thymocytes.Importantly, ECM-mediated interactions also govern the entrance and exit of thymocytes inthe lymphoepithelial complexes named thymic nurse cells. Lastly, pathological conditions,including infectious and autoimmune diseases, in which changes of ECM ligands and receptorsare observed, course with alterations in thymocyte migration and death. In conclusion,the fact that ECM can modulate traffic, differentiation, death and survival of normal thymocytesadds clues for understanding how ECM-mediated interactions behave in the thymus, notonly in normal, but also in pathological conditions.





Autor: Wilson Savino, Sérgio Ranto Dalmau, and Vinícius Cotta Dealmeida

Fuente: https://www.hindawi.com/



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