title: A new dynamic model of CD8+ T effector cell responses via CD4+ T helper-antigen-presenting cells.
abstract: A long-standing paradox in cellular immunology has been the conditional requirement for CD4(+) Th cells in priming of CD8(+) CTL responses. We propose a new dynamic model of CD4(+) Th cells in priming of Th-dependent CD8(+) CTL responses. We demonstrate that OT II CD4(+) T cells activated by OVA-pulsed dendritic cells (DC(OVA)) are Th1 phenotype. They acquire the immune synapse-composed MHC II/OVAII peptide complexes and costimulatory molecules (CD54 and CD80) as well as the bystander MHC class I/OVAI peptide complexes from the DC(OVA) by DC(OVA) stimulation and thus also the potential to act themselves as APCs. These CD4(+) Th-APCs stimulate naive OT I CD8(+) T cell proliferation through signal 1 (MHC I/OVAI/TCR) and signal 2 (e.g., CD54/LFA-1 and CD80/CD28) interactions and IL-2 help. In vivo, they stimulate CD8(+) T cell proliferation and differentiation into CTLs and induce effective OVA-specific antitumor immunity. Taken together, this study demonstrates that CD4(+) Th cells carrying acquired DC Ag-presenting machinery can, by themselves, efficiently stimulate CTL responses. These results have substantial implications for research in antitumor and other aspects of immunity.
authors.affiliation: Research Unit, Saskatchewan Cancer Agency, Department of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. jxiang@scf.sk.ca
authors.forename: Jim
authors.initials: J
authors.lastname: Xiang
authors.forename: Hui
authors.initials: H
authors.lastname: Huang
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology* / Q000378:metabolism*; D024201:Bystander Effect / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D006825:Hybridomas; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008546:Melanoma, Experimental; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018448:Models, Immunological; D008969:Molecular Sequence Data; D009374:Neoplasms, Experimental / Q000235:genetics / Q000276:immunology / Q000517:prevention & control; D010047:Ovalbumin / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism*
chemical_list: D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D018799:Intercellular Adhesion Molecule-1; D010047:Ovalbumin