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Abstract Background Although the contribution of alveolar type II epithelial cell (AEC II) activities in various aspects of respiratory immune regulation has become increasingly appreciated, our understanding of the contribution of AEC II transcriptosome in immunopathologic lung injury remains poorly understood. We have previously established a mouse model for chronic T cell-mediated pulmonary inflammation in which influenza hemagglutinin (HA) is expressed as a transgene in AEC II, in mice expressing a transgenic T cell receptor specific for a class II-restricted epitope of HA. Pulmonary inflammation in these mice occurs as a result of CD4+ T cell recognition of alveolar antigen. This model was utilized to assess the profile of inflammatory mediators expressed by alveolar epithelial target cells triggered by antigen-specific recognition in CD4+ T cell-mediated lung inflammation. Methods We established a method that allows the flow cytometric negative selection and isolation of primary AEC II of high viability and purity. Genome wide transcriptional profiling was performed on mRNA isolated from AEC II isolated from healthy mice and from mice with acute and chronic CD4+ T cell-mediated pulmonary inflammation. Results T cell-mediated inflammation was associated with expression of a broad array of cytokine and chemokine genes by AEC II cell, indicating a potential contribution of epithelial-derived chemoattractants to the inflammatory cell parenchymal infiltration. Morphologically, there was an increase in the size of activated epithelial cells, and on the molecular level, comparative transcriptome analyses of AEC II from inflamed versus normal lungs provide a detailed characterization of the specific inflammatory genes expressed in AEC II induced in the context of CD4+ T cell-mediated pneumonitis. Conclusion An important contribution of AEC II gene expression to the orchestration and regulation of interstitial pneumonitis is suggested by the panoply of inflammatory genes expressed by this cell population, and this may provide insight into the molecular pathogenesis of pulmonary inflammatory states. CD4+ T cell recognition of antigen presented by AEC II cells appears to be a potent trigger for activation of the alveolar cell inflammatory transcriptosome.

Background: Although the contribution of alveolar type II epithelial cell (AEC II) activities in various aspects of respiratory immune regulation has become increasingly appreciated, our understanding of the contribution of AEC II transcriptosome in immunopathologic lung injury remains poorly understood. We have previously established a mouse model for chronic T cell-mediated pulmonary inflammation in which influenza hemagglutinin (HA) is expressed as a transgene in AEC II, in mice expressing a transgenic T cell receptor specific for a class II-restricted epitope of HA. Pulmonary inflammation in these mice occurs as a result of CD4+ T cell recognition of alveolar antigen. This model was utilized to assess the profile of inflammatory mediators expressed by alveolar epithelial target cells triggered by antigenspecific recognition in CD4+ T cell-mediated lung inflammation. Methods: We established a method that allows the flow cytometric negative selection and isolation of primary AEC II of high viability and purity. Genome wide transcriptional profiling was performed on mRNA isolated from AEC II isolated from healthy mice and from mice with acute and chronic CD4+ T cell-mediated pulmonary inflammation. Results: T cell-mediated inflammation was associated with expression of a broad array of cytokine and chemokine genes by AEC II cell, indicating a potential contribution of epithelial-derived chemoattractants to the inflammatory cell parenchymal infiltration. Morphologically, there was an increase in the size of activated epithelial cells, and on the molecular level, comparative transcriptome analyses of AEC II from inflamed versus normal lungs provide a detailed characterization of the specific inflammatory genes expressed in AEC II induced in the context of CD4+ T cell-mediated pneumonitis. Conclusion: An important contribution of AEC II gene expression to the orchestration and regulation of interstitial pneumonitis is suggested by the panoply of inflammatory genes expressed by this cell population, and this may provide insight into the molecular pathogenesis of pulmonary inflammatory states. CD4+ T cell recognition of antigen presented by AEC II cells appears to be a potent trigger for activation of the alveolar cell inflammatory transcriptosome. [ABSTRACT FROM AUTHOR]

Every person harbors a population of potentially self-reactive lymphocytes controlled by tightly balanced tolerance mechanisms. Failures in this balance evoke immune activation and autoimmunity. In this study, we investigated the contribution of self-reactive CD8+ T lymphocytes to chronic pulmonary inflammation and a possible role for naturally occurring CD4+CD25+Foxp3+ regulatory T cells (nTregs) in counterbalancing this process. Using a transgenic murine model for autoimmune-mediated lung disease, we demonstrated that despite pulmonary inflammation, lung-specific CD8+ T cells can reside quiescently in close proximity to self-antigen. Whereas self-reactive CD8+ T cells in the inflamed lung and lung-draining lymph nodes downregulated the expression of effector molecules, those located in the spleen appeared to be partly Ag-experienced and displayed a memory-like phenotype. Because ex vivo-reisolated self-reactive CD8+ T cells were very well capable of responding to the Ag in vitro, we investigated a possible contribution of nTregs to the immune control over autoaggressive CD8+ T cells in the lung. Notably, CD8+ T cell tolerance established in the lung depends only partially on the function of nTregs, because self-reactive CD8+ T cells underwent only biased activation and did not acquire effector function after nTreg depletion. However, although transient ablation of nTregs did not expand the population of self-reactive CD8+ T cells or exacerbate the disease, it provoked rapid accumulation of activated CD103+CD62Llo Tregs in bronchial lymph nodes, a finding suggesting an adaptive phenotypic switch in the nTreg population that acts in concert with other yet-undefined mechanisms to prevent the detrimental activation of self-reactive CD8+ T cells. [ABSTRACT FROM AUTHOR]