T cell receptor β chain dimers on immature thymocytes from normal mice

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Abstract
During T cell development the T cell receptor (TCR) β chain is expressed before the TCRα chain. Experiments in TCRβ transgenic severe combined immune deficiency (SCID) mice have shown that the TCRβ protein can be expressed on the cell surface of immature thymocytes in the absence of the TCRα chain and that the TCRβ protein controls T cell development with regard to cell number, CD4/CD8 expression and allelic exclusion of the TCRβ chain. Subsequent experiments have shown that on the surface of thymocytes fromTCRβ transgenic SCID mice the TCRβ protein can be expressed in a monomelic and dimeric form whereas only the dimeric form was found on the surface of a TCRβ-transfected, immature T cell line. The results presented here show that normal thymocytes from 16-day-old fetuses likewise express only the dimeric form and that the monomelic form on the surface of thymocytes from transgenic mice results from glycosyl phosphatidylinositol linkage. Our results show for the first time that under physiological conditions a TCRβ dimer can be expressed on the cell surface without the TCRα chain.