title: Type II pneumocyte-CD8+ T-cell interactions. Relationship between target cell cytotoxicity and activation.
abstract: CD8+ T-cell responses play an important role in the clearance of respiratory virus infection, but may also contribute to lung injury in the process. The effector mechanisms involved in viral clearance and associated lung injury include both cytolytic and noncytolytic effector functions. Previously we have shown that CD8+ T-cell recognition of alveolar epithelial cells triggers chemokine expression by the epithelial cell and that this plays an important role in the inflammatory infiltration that ensues in the context of T cell-mediated injury (Zhao and colleagues, J. Clin. Invest. 2000;106:R49-R58). In the present study we sought to understand the relationship between alveolar cell cytotoxicity and chemokine expression, both of which occur as a result of CD8+ T-cell antigen recognition. Alveolar epithelial cells efficiently process and present overlapping viral epitopes, and CD8+ T-cell recognition of these class I major histocompatibility complex-restricted epitopes resulted in cytotoxicity of the alveolar cells by both wild-type and perforin-deficient T cells. However, the contribution of perforin-mediated lysis to the total cytotoxicity of alveolar cells by CD8+ T cells was minimal, and the majority of the lysis was attributable to tumor necrosis factor-alpha expressed by the T cell. CD8+ T-cell recognition also led to activation of nuclear factor-kappaB in the alveolar epithelial target cells, at levels inversely proportional to the effector/target (E:T) ratio. Finally, at varying E:T ratios, we demonstrated an inverse relationship between alveolar cell cytotoxicity and monocyte chemotactic protein-1 expression, both of which occur as a result of T-cell recognition. These findings may have important ramifications in understanding the relationship between viral clearance and lung injury.
authors.affiliation: Department of Medicine and the Beirne B. Carter Center for Immunology Research, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
authors.forename: M Q
authors.initials: MQ
authors.lastname: Zhao
authors.forename: M K
authors.initials: MK
authors.lastname: Amir
authors.forename: W R
authors.initials: WR
authors.lastname: Rice
authors.forename: R I
authors.initials: RI
authors.lastname: Enelow
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D000956:Antigens, Viral / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D004847:Epithelial Cells / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D017930:Genes, Reporter; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000378:metabolism; D009980:Influenza A virus / Q000276:immunology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009976:Orthomyxoviridae Infections / Q000276:immunology; D010455:Peptides / Q000276:immunology / Q000494:pharmacology; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014764:Viral Proteins / Q000276:immunology
chemical_list: D000956:Antigens, Viral; D018932:Chemokine CCL2; D000939:Epitopes; D015395:Histocompatibility Antigens Class I; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D010455:Peptides; D052899:Pore Forming Cytotoxic Proteins; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins; D054353:Perforin