title: A synthetic peptide mimicking the HLA-DR beta 2-binding site for CD4 inhibits antigen-independent CD4+ T cell adhesion to B cells and CD4+ T cell activation.
abstract: We studied the ability of a peptide mimicking the major binding site of HLA-DR beta 2 for CD4 (i.e. amino acids 134-148) to inhibit the adhesion of CD4+ T cells to B cells and ICAM-1-DR-expressing fibroblasts, as well as the proliferation of TCR-CD3-triggered CD4+ T cells. Peptide DR134-148 blocked CD4+ T cell (but not CD8+ T cell) binding to B cells and to DR+ ICAM-1+ fibroblasts in a concentration-dependent manner. A peptide composed of randomly associated identical amino acid residues had no effect. This inhibitory activity was not additive with the effect of an anti-CD4 antibody, peptide DR35-46 (mimicking another potential binding site of HLA-DR beta 1 to CD4) or an anti-LFA-1 antibody. Adhesion of a T cell line (HUT78) expressing a mutated form of CD4 unable to bind p56lck cytosine kinase was not inhibited by peptide DR134-148. In addition, herbimycin A, a tyrosine kinase inhibitor, abrogated the inhibitory activity of DR134-148. Since CD4-MHC class II interactions have been shown to play no detectable role in mediating antigen-independent adhesion in this assay, peptide interactions with CD4 may trigger an off signal down-regulating LFA-1-mediated adhesion. Indeed, adhesion of CD4+ T cells to ICAM-1- fibroblasts was not inhibited by peptide DR134-148, while the same peptide inhibited antigen (protein-pure derivative)- and anti-CD3 antibody-induced CD4 T cell proliferation. These findings suggest that the major sequence involved in the MHC class II interaction with CD4 is sufficient to induce a downstream negative regulatory signal that is mediated by p56lck, independently of antigen-specific TCR triggering.
authors.affiliation: INSERM U429, Hopital Necker-Enfants-Malades, Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Mazerolles
authors.forename: C
authors.initials: C
authors.lastname: Barbat
authors.forename: A
authors.initials: A
authors.lastname: Fischer
mesh_terms: D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D001667:Binding, Competitive / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002450:Cell Communication / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D002472:Cell Transformation, Viral; D000939:Epitopes / Q000187:drug effects / Q000494:pharmacology; D006684:HLA-DR Antigens / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects*; D018716:Molecular Mimicry / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology* / Q000494:pharmacology*; D011485:Protein Binding / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism
chemical_list: D017252:CD3 Complex; D015704:CD4 Antigens; D000939:Epitopes; D006684:HLA-DR Antigens; D010446:Peptide Fragments; D011505:Protein-Tyrosine Kinases