CD6: expression during development, apoptosis and selection of human and mouse thymocytes.
CD6, a 130-kDa surface glycoprotein, is expressed primarily on cells of T lineage. A co-stimulatory role for CD6 in mature T cells has been shown, but the function of CD6 during thymocyte development is unknown. Since CD6 ligands are expressed on thymic epithelium, their interactions with CD6 could be important in thymic selection. In this report we show that CD6 is developmentally regulated in human and mouse thymocytes, and further demonstrate that increase in the level of CD6 expression correlates with expression of the selection marker CD69. We also show that activation via CD2 induces CD6 expression on mature human thymocytes and on a subset of immature human thymocytes that are resistant to apoptosis. In human and mouse thymocytes that express heterogeneous TCR, CD6 increases occur as double-positive thymocytes are selected to a single-positive stage. In contrast, in thymocytes from TCR transgenic mice, CD6 is barely increased following selection, suggesting that as functional avidity increases, requirements for CD6-dependent co-stimulation decrease. Taken together, these results indicate that during thymic development CD6-dependent signals may contribute both to thymocyte survival, and to the overall functional avidity of selection in both man and mouse.
Singer
Nora G
NG
Case Western Reserve University School of Medicine and Rainbow Babies and Children's Hospital/University Hospitals of Cleveland, Cleveland, OH 44106, USA. ngs@po.cwru.edu
Fox
David A
DA
Haqqi
Tariq M
TM
Beretta
Laura
L
Endres
Judith S
JS
Prohaska
Susan
S
Parnes
Jane R
JR
Bromberg
Jonathan
J
Sramkoski
R Michael
RM
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D017209:Apoptosis / Q000276:immunology*; D018801:CD2 Antigens / Q000378:metabolism; D002454:Cell Differentiation; D002470:Cell Survival; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology*
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; C062279:CD6 antigen; D011948:Receptors, Antigen, T-Cell