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Developmental Immunology
Volume 7 (2000), Issue 2-4, Pages 279-291
http://dx.doi.org/10.1155/2000/60247

Role of Extracellular Matrix-Mediated Interactions in Thymocyte Migration

1Laboratory on Thymus Research, Department of Immunology, Oswaldo Cruz Institute – Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
2Department 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
3Laboratory of Cell Biology, Department of Ultrastructure and Cell Biology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
4Laboratory 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 of biological responses that can be elicited by ligation of extracellular matrix components to their corresponding receptors. As regards the physiology of the thymus, cell migration is a crucial event in the general process of T cell differentiation. Studies on the intrathymic distribution of ECM components revealed that fibronectin, laminin and type IV collagen, are not restrictedly located at typical basement membrane sites, also forming a thick network in the medullary region of the thymic lobules, whereas very thin ECM fibers are found within the cortex. These ECM components are essentially produced by thymic microenvironmental cells, which also drive thymocyte differentiation. Signals triggered by ECM are conveyed into thymocytes or microenvironmental cells through specific membrane receptors, and most of them belong to the integrin type, such as the VLA-3, VLA-4, VLA-5 and VLA-6. In vitro studies revealed that adhesion of thymocytes to thymic microenvironmental cells is mediated by extracellular matrix. Such an adhesion is preferentially done by immature thymocytes. Importantly, ECM-mediated interactions also govern the entrance and exit of thymocytes in the lymphoepithelial complexes named thymic nurse cells. Lastly, pathological conditions, including infectious and autoimmune diseases, in which changes of ECM ligands and receptors are observed, course with alterations in thymocyte migration and death. In conclusion, the fact that ECM can modulate traffic, differentiation, death and survival of normal thymocytes adds clues for understanding how ECM-mediated interactions behave in the thymus, not only in normal, but also in pathological conditions.