title: Inhibition of activated/memory (CD45RO(+)) T cells by oxidative stress associated with block of NF-kappaB activation.
abstract: Impaired immune responses in cancer patients have been associated with oxidative stress. Increased levels of reactive oxygen species released from activated, tumor-infiltrating macrophages or granulocytes may therefore constitute a hurdle for effective immunotherapy against cancer. In this study, we investigated functional consequences and molecular events in T cells exposed to low levels of oxidative stress. We observed that cytokine production of human PBMC, upon stimulation with an HLA-A*0201-restricted influenza peptide and nonspecific receptor cross-linking, was reduced after exposure to micromolar levels of H2O2. Functional impairment as measured by IFN-gamma release occurred earlier and at lower doses of exogenously added H2O2 than required to induce apoptosis. This suggests that there is a dose window of oxidative stress leading to T cell unresponsiveness in the absence of apoptosis. The reduction of Th1 cytokines, induced by H2O2, was predominantly observed in memory/effector (CD45RO(+)) T cells and correlated with a block in NF-kappaB activation. IL-10 production was more profoundly influenced by low doses of H2O2 than IFN-gamma, TNF-alpha, and IL-2. The influence of H2O2 on production of IL-10 was not significantly different between memory/activated and naive T cells. These observations suggest that Th1 and Th2 cytokines are differently regulated under conditions of oxidative stress. Taken together, these findings may explain why Ag-experienced, CD45RO(+), T cells found in the tumor milieu are functionally suppressed.
authors.affiliation: Immune and Gene Therapy Laboratory, Department of Oncology and Pathology, Cancer Center Karolinska, Stockholm, Sweden. kalle.malmberg@cck.ki.se
authors.forename: K J
authors.initials: KJ
authors.lastname: Malmberg
authors.forename: V
authors.initials: V
authors.lastname: Arulampalam
authors.forename: F
authors.initials: F
authors.lastname: Ichihara
authors.forename: M
authors.initials: M
authors.lastname: Petersson
authors.forename: K
authors.initials: K
authors.lastname: Seki
authors.forename: T
authors.initials: T
authors.lastname: Andersson
authors.forename: R
authors.initials: R
authors.lastname: Lenkei
authors.forename: G
authors.initials: G
authors.lastname: Masucci
authors.forename: S
authors.initials: S
authors.lastname: Pettersson
authors.forename: R
authors.initials: R
authors.lastname: Kiessling
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007156:Immunologic Memory; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D008213:Lymphocyte Activation; D016328:NF-kappa B / Q000378:metabolism*; D009369:Neoplasms / Q000276:immunology / Q000378:metabolism; D018384:Oxidative Stress; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D016207:Cytokines; D007376:Interleukin-2; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D007371:Interferon-gamma; D006861:Hydrogen Peroxide; D017493:Leukocyte Common Antigens