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Developmental Immunology
Volume 5 (1998), Issue 4, Pages 247-261

The Avian Transcription Factor c-Rel is Expressed in Lymphocyte Precursor Cells and Antigen-Presenting Cells During Thymus Development

1Laboratoire d'Oncologie Moléculaire, URA1160, Institut de Biologie de Lille, 1 rue Calmette, Lille Cedex 59019, France
2Department of Microbiology, State University of New York at Stony Brook, New York 11794, USA

Received 6 January 1997; Revised 5 June 1997; Accepted 18 June 1997

Copyright © 1998 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.


Transcription factors of the Rel/NF-κB family are widely involved in the immune system. In this study, we investigate the in vivo expression of the avian protein c-Rel in the T-cell lineage during thymus development. The majority of thymocytes do not express the c-Rel protein. However, lymphocyte precursor cells that colonize the thymus express the c-Rel protein shortly after their homing in the organ and before they begin to differentiate, c-Rel is also detected in different subsets of,antigen-presenting cells such as epithelial cells, dendritic cells, and macrophages. In vitro studies have shown that Rel/NF-κB proteins are sequestered in an inactive form in the cytoplasm by interaction with the IκBα inhibitory protein. By immunocytochemistry, we show that in vivo c-Rel is localized in the cytoplasm of antigen-presenting cells but in both the cytoplasm and nucleus of lymphocyte precursor cells. The cytoplasmic localization of c-Rel in antigen-presenting cells correlates with a high expression of IκBα, whereas the nuclear localization of c-Rel in lymphocyte precursor cells correlates with a much lower expression of IκBα. These results suggest that c-Rel might be constitutively activated in lymphocyte precursor cells.