TCR internalization induced by peptide/MHC ligands requires the transmembrane domains of alphabeta chains of TCR, but not the expression of CD8 and Thy-1 molecules.
T-cell receptor (TCR) internalization occurs via TCR recognition of the peptide/MHC molecule complex on antigen presenting cell (APC). In this study, the requirements for inducing the internalization of TCR molecules on Ld major histocompatibility complex (MHC) class I-restricted T-cells were investigated with 2C cytotoxic T-lymphocyte (CTL) clones with defined peptides as the antigen. To evaluate the function of the transmembrane region of TCR alphabeta chains in TCR internalization, we generated T-cell transfectants expressing the wild type and glycosylphosphatidyl inositol (GPI)-linked form of 2C TCR. Among all peptides forming proper ligands to 2C TCR, only the Qp2Ca peptide induced TCR internalization, which was known to have the highest affinity to both Ld MHC class I molecules and TCR in association with Ld molecules. Such TCR internalization was not observed in cells expressing the GPI-linked form of 2C TCR. Furthermore, the expression of CD8 coreceptor and Thy-1 accessory molecules were both not required for Qp2Ca-induced TCR internalization, and these molecules did not accompany TCR internalization. Altogether, these results suggest that TCR internalization on CTL is not a prerequisite for CTL function.