TCR internalization induced by peptide/MHC ligands requires the transmembrane domains of alpha beta chains of TCR, but not the expression of CD8 and Thy-1 molecules

T-cell receptor (TCR) internalization occurs via TCR recognition of the pep tide/MHC molecule complex on antigen presenting cell (APC), In this study, the requirements for inducing the internalization of TCR molecules on L-d m ajor histocompatibility complex (MHC) class I-restricted T-cells were inves tigated with 2C cytotoxic T-lymphocyte (CTL) clones with defined peptides a s the antigen, To evaluate the function of the transmembrane region of TCR cup chains in TCR internalization, we generated T-cell transfectants expres sing the wild type and glycosylphosphatidyl inositol (GPI)-linked form of 2 C TCR, Among all peptides forming proper ligands to 2C TCR, only the Qp2Ca peptide induced TCR internalization, which was known to have the highest af finity to both L-d MHC class I molecules and TCR in association with L-d mo lecules. Such TCR internalization was not observed in cells expressing the GPI-linked form of 2C TCR, Furthermore, the expression of CD8 coreceptor an d Thy-1 accessory molecules were both not required for Qp2Ca-induced TCR in ternalization, and these molecules did not accompany TCR internalization. A ltogether, these results suggest that TCR internalization on CTL is not a p rerequisite for CTL function.