title: The T8 antigen is a multimeric complex of two distinct subunits on human thymocytes but consists of homomultimeric forms on peripheral blood T lymphocytes.
abstract: Monoclonal antibodies allow for the detection of structures on the cell surface of human cytotoxic thymus-derived lymphocytes, which are involved in their function. Among these cell surface components, T8 is of particular interest, since it is required during the recognition of target cells by a subset of human cytotoxic T lymphocytes. The only other cell types on which T8 has been detected are functionally inert thymocytes. Here we demonstrate that T8 isolated from peripheral blood T lymphocytes is different from thymocyte T8. On peripheral blood T lymphocytes T8 was found in multimeric forms of a 34-kDa glycoprotein. These forms were also found on thymocytes, but in addition multimeric complexes of the 34-kDa T8 with a 46-kDa protein were detected. Preliminary chemical analyses showed that the 34-kDa and the 46-kDa forms differ in both their protein and carbohydrate structures. The 46-kDa structure was found to be distinct from the major thymocyte antigen T10. The interchain disulfide bridges between the 34-kDa T8 polypeptide are located in the 24-kDa CNBr fragment, which contains a hydrophobic region. Two (14 kDa and 20 kDa) of the three CNBr fragments of the 46-kDa T8 subunit were found to be involved in interchain disulfide bridging with the 34-kDa T8 species. We suggest that the switch from heteromultimers to homomultimers may occur concomitantly with the last step in T lymphocyte maturation.
mesh_terms: D000954:Antigens, Surface / Q000032:analysis*; D001665:Binding Sites; D003488:Cyanogen Bromide; D004220:Disulfides / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007525:Isoelectric Focusing; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D013601:T-Lymphocytes / Q000032:analysis*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000954:Antigens, Surface; D004220:Disulfides; D010446:Peptide Fragments; D003488:Cyanogen Bromide