title: On the site and mode of antigen presentation for the initiation of clonal expansion of CD8 T cells specific for a natural tumor antigen.
abstract: Because of the low frequency of antigen-specific T cells, early events in the activation of tumor-specific T cells in vivo have not been well characterized. There is still no direct documentation on where the clonal expansion begins and how tumor antigens are presented to the host CD8 T cells to initiate it. Here we used transgenic T cells specific for a natural tumor antigen P1A to evaluate the kinetics, location, and modes of antigen presentation for initiating CTL response in vivo. Our results demonstrate that the initial activation of P1A-specific T cells takes place in the lymphoid organs. The activated T cells then migrate into tumors, where they undergo accelerated division and acquire distinct activation markers. The site of initiation cannot be altered by either local expression of costimulatory molecules or by intratumor injection of naïve T cells. Moreover, using genetic models that allow only one mode of antigen presentation, we show here that both cross-presentation of P1A by the host antigen-presenting cells, and direct antigen presentation and costimulation by the tumor cells are sufficient to initiate rapid T cell-clonal expansion in the lymphoid organ. These results provide direct evidence for two fundamental assumptions on the mechanisms of T-cell activation in vivo.
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, Ohio State University Medical Center, Columbus, Ohio 43210, USA.
authors.forename: X F
authors.initials: XF
authors.lastname: Bai
authors.forename: J X
authors.initials: JX
authors.lastname: Gao
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Wen
authors.forename: P
authors.initials: P
authors.lastname: Zheng
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D016130:Immunophenotyping; D016219:Immunotherapy, Adoptive; D019041:L-Selectin / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D008822:Mice, Transgenic; D010954:Plasmacytoma / Q000276:immunology; D013154:Spleen / Q000276:immunology / Q000473:pathology
chemical_list: D000951:Antigens, Neoplasm; D018122:B7-1 Antigen; D018984:Epitopes, T-Lymphocyte; C076546:tumor rejection antigen P815A, mouse; D019041:L-Selectin