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Redox Regulation of T cell Activation and Function During Viral Infection

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The goal of the work presented here was to provide insight into the role of reactive oxygen intermediates (ROI) during T cell activation and the importance of their regulation during an immune response. ROI generated in response to receptor stimulation play an important role in mediating cellular responses. We have examined the importance of reversible cysteine sulfenic acid formation in naïve CD8+ T cell activation and proliferation. We observed that within minutes of T cell activation, naïve CD8+ T cells increased ROI levels in a manner dependent upon antigen concentration. Increased ROI resulted in elevated levels of cysteine sulfenic acid in the total proteome. Analysis of specific proteins revealed that the protein tyrosine phosphatases SHP-1 and SHP-2, as well as actin, underwent increased sulfenic acid modification following stimulation. To examine the contribution of reversible cysteine sulfenic acid formation to T cell activation increasing concentrations of 5, 5 dimethyl-1,3-cyclohexanedione (dimedone), which covalently binds to cysteine sulfenic acid, were added to cultures. Subsequent experiments demonstrated that the reversible formation of cysteine sulfenic acid was critical for ERK1/2 phosphorylation, calcium flux, cell growth, and proliferation of naïve CD8+ and CD4+ T cells. We also found that TNFα production by effector and memory CD8+ T cells was more sensitive to inhibition of reversible cysteine sulfenic acid formation than IFNγ. Together, these results demonstrate that reversible cysteine sulfenic acid formation is an important regulatory mechanism by which CD8+ T cells are able to modulate signaling, proliferation, and function. Understanding the mechanisms that regulate cellular growth and proliferation are critical for developing therapeutic strategies to modulate immune responses, the expansion of cancer cells, and the development of autoimmune disorders. Since previous studies have implied a role for ROI in these conditions, we hypothesized understanding their regulation is critical for determining their contribution to these diseases. Because T cells exhibit massive clonal expansion similar to cancer cells, these cells are a model system to study the contribution of ROI to cellular growth, proliferation, and differentiation. However, the effect of increased ROI on an adaptive immune response is unknown. Following TCR stimulation, the expression and oxidation of peroxiredoxin II (PrdxII), a critical antioxidant enzyme, increased in CD8+ T cells. In contrast, PrdxII expression was decreased in effector cells at day 8 post acute viral infection. Deletion of PrdxII increased ROI, proliferation, and death during in vitro division. Activated CD8+ T cells from PrdxII deficient mice were resistant to Fas-Ligand induced apoptosis, but susceptible to death-induced by TCR crosslinking. During acute viral infection, the number of effector CD8+ T cells in PrdxII-/- mice was increased, while memory cells were similar to wild-type mice. Following chronic viral infection, increased antigen specific CD8+ T cells were observed in the livers of PrdxII null mice. Virus specific cells maintained cytokine production and caused lethal liver damage. These results demonstrate PrdxII controls CD8+ T cell proliferation, differentiation, and immunopathology.
T cells
Michalek, Ryan (author)
Leslie B. Poole (committee chair)
Jason M. Grayson (committee member)
Martha Alexander-Miller (committee member)
Elizabeth M. Hiltbold (committee member)
David A. Ornelles (committee member)
2009-03-19T14:10:54Z (accessioned)
2010-06-18T18:57:23Z (accessioned)
2009-03-19T14:10:54Z (available)
2010-06-18T18:57:23Z (available)
2009-03-19T14:10:54Z (issued)
Microbiology & Immunology (discipline)
http://hdl.handle.net/10339/14690 (uri)
en_US (iso)
Wake Forest University
Release the entire work for access only to the Wake Forest University system for one year from the date below. After one year, release the entire work for access worldwide. (accessRights)
Redox Regulation of T cell Activation and Function During Viral Infection

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