International Immunology Advance Access originally published online on January 15, 2009
International Immunology 2009 21(2):167-177; doi:10.1093/intimm/dxn135
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Absence of CD47 in vivo influences thymic dendritic cell subset proportions but not negative selection of thymocytes
1 Research Centre, Maisonneuve-Rosemont Hospital
2 Department of Microbiology and Immunology
3 Department of Medicine, University of Montreal
4 Centres hospitalier de l'Université de Montréal (CHUM) Research Centre, 5415, boulevard de l'Assomption, Montreal, Quebec H1T 2M4, Canada
Correspondence to: S. Lesage; E-mail: sylvie.lesage{at}umontreal.ca
CD47 is a ubiquitously expressed molecule which has been attributed a role in many cellular processes. Its role in preventing cellular phagocytosis has defined CD47 as an obligatory self-molecule providing a ‘don't-eat-me-signal’. Additionally, CD47–CD172a interactions are important for cellular trafficking. Yet, the contribution of CD47 to T cell stimulation remains controversial, acting sometimes as a co-stimulator and sometimes as an inhibitor of TCR signalling or peripheral T cell responses. Most of the experiments leading to this controversy have been carried in in vitro systems. Moreover, the role of CD47 on thymocyte differentiation, which precisely relies on TCR signal strength, has not been evaluated. Here, we examine the in vivo role of CD47 in T cell differentiation using CD47-deficient mice. We find that, in the absence of CD47, thymocyte positive and negative selection processes are not altered. Indeed, our data demonstrate that the absence of CD47 does not influence the strength of TCR signalling in thymocytes. Furthermore, in agreement with a role for CD47–CD172a interactions in CD172a+ dendritic cell migration, we report a reduced proportion of thymic dendritic cells expressing CD172a in CD47-deficient mice. As the total proportion of dendritic cells is maintained, this creates an imbalance in the proportion of CD172a+ and CD172alow dendritic cells in the thymus. Together, these data indicate that the altered proportion of thymic dendritic cell subsets does not have a primordial influence on thymic selection processes.
Keywords: CD172a, DC subsets, T cells
* These authors contributed equally to this study.
Transmitting editor: A. Singer
Received 5 July 2008, accepted 25 November 2008.