<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nguyen, D. H.</style></author><author><style face="normal" font="default" size="100%">Hurtado-Ziola, N.</style></author><author><style face="normal" font="default" size="100%">Gagneux, P.</style></author><author><style face="normal" font="default" size="100%">Ajit Varki</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Loss of Siglec expression on T lymphocytes during human evolution</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proceedings of the National Academy of Sciences of the United States of America</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">*Biological Evolution</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens</style></keyword><keyword><style  face="normal" font="default" size="100%">B-Lymphocytes/cytology/immunology</style></keyword><keyword><style  face="normal" font="default" size="100%">Calcium/metabolism</style></keyword><keyword><style  face="normal" font="default" size="100%">CD/*immunology</style></keyword><keyword><style  face="normal" font="default" size="100%">Cell Proliferation</style></keyword><keyword><style  face="normal" font="default" size="100%">Differentiation</style></keyword><keyword><style  face="normal" font="default" size="100%">Down-Regulation</style></keyword><keyword><style  face="normal" font="default" size="100%">Humans</style></keyword><keyword><style  face="normal" font="default" size="100%">Lectins/*immunology</style></keyword><keyword><style  face="normal" font="default" size="100%">Lymphocyte Activation</style></keyword><keyword><style  face="normal" font="default" size="100%">Myelomonocytic/*immunology</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">May 16</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/16682635</style></url></web-urls></urls><number><style face="normal" font="default" size="100%">20</style></number><edition><style face="normal" font="default" size="100%">2006/05/10</style></edition><volume><style face="normal" font="default" size="100%">103</style></volume><pages><style face="normal" font="default" size="100%">7765-70</style></pages><isbn><style face="normal" font="default" size="100%">0027-8424 (Print)0027-84</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;We report here that human T cells give much stronger proliferative responses to specific activation via the T cell receptor (TCR) than those from chimpanzees, our closest evolutionary relatives. Nonspecific activation using phytohemagglutinin was robust in chimpanzee T cells, indicating that the much lower response to TCR simulation is not due to any intrinsic inability to respond to an activating stimulus. CD33-related Siglecs are inhibitory signaling molecules expressed on most immune cells and are thought to down-regulate cellular activation pathways via cytosolic immunoreceptor tyrosine-based inhibitory motifs. Among human immune cells, T lymphocytes are a striking exception, expressing little to none of these molecules. In stark contrast, we find that T lymphocytes from chimpanzees as well as the other closely related &quot;great apes&quot; (bonobos, gorillas, and orangutans) express several CD33-related Siglecs on their surfaces. Thus, human-specific loss of T cell Siglec expression occurred after our last common ancestor with great apes, potentially resulting in an evolutionary difference with regard to inhibitory signaling. We confirmed this by studying Siglec-5, which is prominently expressed on chimpanzee lymphocytes, including CD4 T cells. Ab-mediated clearance of Siglec-5 from chimpanzee T cells enhanced TCR-mediated activation. Conversely, primary human T cells and Jurkat cells transfected with Siglec-5 become less responsive; i.e., they behave more like chimpanzee T cells. This human-specific loss of T cell Siglec expression associated with T cell hyperactivity may help explain the strikingly disparate prevalence and severity of T cell-mediated diseases such as AIDS and chronic active hepatitis between humans and chimpanzees.&lt;/p&gt;
</style></abstract><work-type><style face="normal" font="default" size="100%">Research Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov&#039;t</style></work-type><accession-num><style face="normal" font="default" size="100%">16682635 PMID</style></accession-num><notes><style face="normal" font="default" size="100%">&lt;p&gt;Proc Natl Acad Sci U S A. 2006 May 16;103(20):7765-70. Epub 2006 May 8&lt;/p&gt;
</style></notes><custom2><style face="normal" font="default" size="100%">1472519</style></custom2><auth-address><style face="normal" font="default" size="100%">Glycobiology Research and Training Center and Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA.</style></auth-address></record></records></xml>