T-CELL RECEPTOR BETA-CHAIN DIMERS ON IMMATURE THYMOCYTES FROM NORMAL MICE

During T cell development the T cell receptor (TCR) beta chain is expr essed before the TCRalpha chain. Experiments in TCRbeta transgenic sev ere combined immune deficiency (SCID) mice have shown that the TCRbeta protein can be expressed on the cell surface of immature thymocytes i n the absence of the TCRalpha chain and that the TCRbeta protein contr ols T cell development with regard to cell number, CD4/CD8 expression and allelic exclusion of the TCRbeta chain. Subsequent experiments hav e shown that on the surface of thymocytes from TCRbeta transgenic SCID mice the TCRbeta protein can be expressed in a monomeric and dimeric form whereas only the dimeric form was found on the surface of a TCRbe ta-transfected, immature T cell line. The results presented here show that normal thymocytes from 16-day-old fetuses likewise express only t he dimeric form and that the monomeric form on the surface of thymocyt es from transgenic mice results from glycosyl phosphatidylinositol lin kage. Our results show for the first time that under physiological con ditions a TCRbeta dimer can be expressed on the cell surface without t he TCRalpha chain.