Antigen-T Lymphocyte Interactions in the Induction of Functional Unresponsiveness

In the initiation of an immune response helper/inducer T lymphocytes are activated by antigen presented in association with Class II major histocompatibility complex (MHC) gene products1,2 Even though there is now extensive information on the structure of both MHC Class II determinants3,4 and the T cell receptor5,6 their physical interaction with antigen in the induction of an activation signal is unclear. As a preliminary step in the analysis of receptor antigen interactions it is necessary to demonstrate specific binding of that ligand to the appropriate receptor. Recently employing T lymphocyte clones reactive with defined antigens the specific binding to T cells of antigen in the presence of antigen presenting cells7 or in isolation8,9 has been reported. We have isolated human T lymphocyte clones reactive with a 24 amino acid peptide (p20) located at the carboxyl terminus (306–329) of the HA-1 molecule of influenza virus haemagglutinin (HA)10, that after incubation with a supraimmunogenic concentration of p20 in the absence of presenting cells fail to respond to an immunogenic challenge11.