THY3, A DEVELOPMENTALLY-REGULATED T-CELL GLYCOPROTEIN ASSOCIATED TO THY-1 IN DETERGENT-RESISTANT MEMBRANE MICRODOMAINS

The function of the Thy-1 molecule, a major T-cell glycoprotein, is st ill obscure. Its functional properties might be due to the anchoring v ia a glycosylphosphatidylinositol group which favors gathering of mole cules in functional membrane subregions called microdomains. Using nov el monoclonal antibodies, we describe a 53-kDa Thy-1-associated glycop rotein called Thy-3. Thy-3 expression is restricted to T lymphocytes, becomes detectable on double-positive thymocytes, and depends on that of Thy-1. Anti-Thy-3 antibodies immunoprecipitate Thy-1 and Thy-3 or T hy-3 alone in detergents which preserve or disrupt microdomains, respe ctively. These antibodies induce thymocyte aggregation and interfere w ith adhesion of thymocytes to a thymic epithelial cell line as previou sly shown with anti-Thy-1 antibodies. Thus, Thy-3 is a T lineage-speci fic glycoprotein associated to Thy-1 in membrane microdomains and migh t contribute to the function of Thy-1 in T-cell differentiation. (C) 1 997 Academic Press.