title: Effects of epitope modification on T cell receptor-ligand binding and antigen recognition by seven H-2Kd-restricted cytotoxic T lymphocyte clones specific for a photoreactive peptide derivative.
abstract: We tested for antigen recognition and T cell receptor (TCR)-ligand binding 12 peptide derivative variants on seven H-2Kd-restricted cytotoxic T lymphocytes (CTL) clones specific for a bifunctional photoreactive derivative of the Plasmodium berghei circumsporozoite peptide 252-260 (SYIPSAEKI). The derivative contained iodo-4-azidosalicylic acid in place of PbCS S-252 and 4-azidobenzoic acid on PbCS K-259. Selective photoactivation of the N-terminal photoreactive group allowed crosslinking to Kd molecules and photoactivation of the orthogonal group to TCR. TCR photoaffinity labeling with covalent Kd-peptide derivative complexes allowed direct assessment of TCR-ligand binding on living CTL. In most cases (over 80%) cytotoxicity (chromium release) and TCR-ligand binding differed by less than fivefold. The exceptions included (a) partial TCR agonists (8 cases), for which antigen recognition was five-tenfold less efficient than TCR-ligand binding, (b) TCR antagonists (2 cases), which were not recognized and capable of inhibiting recognition of the wild-type conjugate, (c) heteroclitic agonists (2 cases), for which antigen recognition was more efficient than TCR-ligand binding, and (d) one partial TCR agonist, which activated only Fas (C1)95), but not perforin/granzyme-mediated cytotoxicity. There was no correlation between these divergences and the avidity of TCR-ligand binding, indicating that other factors than binding avidity determine the nature of the CTL response. An unexpected and novel finding was that CD8-dependent clones clearly incline more to TCR antagonism than CD8-independent ones. As there was no correlation between CD8 dependence and the avidity of TCR-ligand binding, the possibility is suggested that CD8 plays a critical role in aberrant CTL function.
authors.affiliation: Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Epalinges, Switzerland.
authors.forename: B M
authors.initials: BM
authors.lastname: Kessler
authors.forename: P
authors.initials: P
authors.lastname: Bassanini
authors.forename: J C
authors.initials: JC
authors.lastname: Cerottini
authors.forename: I F
authors.initials: IF
authors.lastname: Luescher
mesh_terms: D000345:Affinity Labels; D000595:Amino Acid Sequence; D018414:CD8-Positive T-Lymphocytes; D002460:Cell Line; D002999:Clone Cells; D006183:H-2 Antigens / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D019014:fas Receptor / Q000276:immunology
chemical_list: D000345:Affinity Labels; D006183:H-2 Antigens; C024755:H-2K(K) antigen; D008562:Membrane Glycoproteins; D010455:Peptides; D052899:Pore Forming Cytotoxic Proteins; D011948:Receptors, Antigen, T-Cell; D019014:fas Receptor; D054353:Perforin