title: Potent T cell activation with dimeric peptide-major histocompatibility complex class II ligand: the role of CD4 coreceptor.
abstract: The interaction of the T cell receptor (TCR) with its cognate peptide-major histocompatibility complex (MHC) on the surface of antigen presenting cells (APCs) is a primary event during T cell activation. Here we used a dimeric IEk-MCC molecule to study its capacity to activate antigen-specific T cells and to directly analyze the role of CD4 in physically stabilizing the TCR-MHC interaction. Dimeric IEk-MCC stably binds to specific T cells. In addition, immobilized dimeric IEk-MCC can induce TCR downregulation and activate antigen-specific T cells more efficiently than anti-CD3. The potency of the dimeric IEk-MCC is significantly enhanced in the presence of CD4. However, CD4 does not play any significant role in stabilizing peptide-MHC-TCR interactions as it fails to enhance binding of IEk-MCC to specific T cells or influence peptide-MHC-TCR dissociation rate or TCR downregulation. Moreover, these results indicate that dimerization of peptide-MHC class II using an IgG molecular scaffold significantly increases its binding avidity leading to an enhancement of its stimulatory capacity while maintaining the physiological properties of cognate peptide-MHC complex. These peptide-MHC-IgG chimeras may, therefore, provide a novel approach to modulate antigen-specific T cell responses both in vitro and in vivo.
authors.affiliation: Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Hamad
authors.forename: S M
authors.initials: SM
authors.lastname: O'Herrin
authors.forename: M S
authors.initials: MS
authors.lastname: Lebowitz
authors.forename: A
authors.initials: A
authors.lastname: Srikrishnan
authors.forename: J
authors.initials: J
authors.lastname: Bieler
authors.forename: J
authors.initials: J
authors.lastname: Schneck
authors.forename: D
authors.initials: D
authors.lastname: Pardoll
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D015536:Down-Regulation; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology*; D008285:Major Histocompatibility Complex; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D008024:Ligands; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins