GITR expression on T-cell receptor-stimulated human CD8+ T cell in a JNK-dependent pathway

Glucocorticoid-induced tumor necrosis factor receptor (TNFR) (GITR) family-related gene is a member of the TNFR super family. GITR works as one of the immunoregulatory molecule on CD4+ regulatory T cells and has an important role on cell survival or cell death in CD4+ T cells. Little is known about the expression of GITR on human CD8+ T cells on antigen-specific and non-specific activation. Here, we report that expression of GITR on human CD8+ T cells on T-cell receptor (TCR) (anti-CD3)-mediated stimulation is dependent on the JNK pathway. The activation of CD8+ T cells was measured by the expression of IL-2 receptor-\u3b1 (CD25), GITR and by IFN-\u3b3 production upon re-stimulation with anti-CD3 antibody. We studied the signaling pathway of such inducible expression of GITR on CD8+ T cells. We found that a known JNK-specific inhibitor, SP600125, significantly down-regulates GITR expression on anti-CD3 antibody-mediated activated CD8+ T cells by limiting JNK phosphorylation. Subsequently, after stimulation of the CD8+ cells, we tested for the production of IFN-\u3b3 by the activated cells following restimulation with the same stimulus. It appears that the expression of GITR on activated human CD8+ T cells might also be regulated through the JNK pathway when the activation is through TCR stimulation. Therefore, GITR serves as an activation marker on activated CD8+ cells and interference with JNK phosphorylation, partially or completely, by varying the doses of SP600125 might have implications in CD8+ cytotoxic T cell response in translational research

CD4⁺CD25⁻ T Cells Transduced to Express MHC Class I-Restricted Epitope-Specific TCR Synthesize Th1 Cytokines and Exhibit MHC Class I-Restricted Cytolytic Effector Function in a Human Melanoma Model

Cytolytic T cell-centric active specific and adoptive immunotherapeutic approaches might benefit from the simultaneous engagement of CD4⁺ T cells. Considering the difficulties in simultaneously engagingCD4⁺ and CD8⁺ T cells in tumor immunotherapy, especially in an Ag-specific manner, redirecting CD4⁺ T cells to MHC class I-restricted epitopes through engineered expression of MHC class I-restricted epitope-specific TCRs in CD4⁺ T cells has emerged as a strategic consideration. Such TCR-engineered CD4⁺ T cells have been shown to be capable of synthesizing cytokines as well as lysing target cells. We have conducted a critical examination of functional characteristics of CD4⁺ T cells engineered to express the α- and β-chains of a high functional avidity TCR specific for the melanoma epitope, MART-1, as a prototypic human tumor Ag system. We found that unpolarized CD4⁺CD25⁻ T cells engineered to express the MART-1 TCR selectively synthesize Th1 cytokines and exhibit a potent Ag-specific lytic granule exocytosis-mediated cytolytic effector function of comparable efficacy to that of CD8⁺ CTL. Such TCR engineered CD4⁺ T cells, therefore, might be useful in clinical immunotherapy

Immunoregulation through IL-10 gene expression and the fate of cytotoxic T lymphocyte-mediated tumor immunotherapy

Gene analysis of tumor associated antigens revealed that tumor antigens are all normal gene product. Inducing tumor reactive cytotoxic T lymphocytes (CT) in the patients is same as inducing autoimmunity in the patients. Immunosuppressive cytokine interleukin-10 (IL-10) plays an important role in maintaining homeostasis or tolerance. To break the tumor tolerance, blocking and IL-10 secretion or intervention in the pathways of IL-10 gene activation is indeed important

T Cells Expanded in Presence of IL-15 Exhibit Increased Antioxidant Capacity And Innate Effector Molecules

Persistence of effector cytotoxic T lymphocytes (CTLs) during an immunological response is critical for successfully controlling a viral infection or tumor growth. Various cytokines are known to play an important part in regulating the immune response. The IL-2 family of cytokines that includes IL-2 and IL-15 are known to function as growth and survival factors for antigen-experienced T cells. IL-2 and IL-15 possess similar properties, including the ability to induce T cell proliferation. Whereas long term IL-2 exposure has been shown to promote apoptosis and limit CD8+ memory T cell survival and proliferation, it is widely believed that IL-15 can inhibit apoptosis and helps maintain a memory CD8+ T-cell population. However, mechanisms for superior outcomes for IL-15 as compared to IL-2 are still under investigation. Our data shows that human T cells cultured in the presence of IL-15 exhibit increased expression of anti-oxidant molecules Glutathione reductase (GSR), Thioredoxin reductase 1 (TXNDR1), Peroxiredoxin (PRDX), Superoxide dismutase (SOD). An increased expression of cell-surface thiols, intracellular glutathione, and thioredoxins was also noted in IL-15 cultured T cells. Additionally, IL-15 cultured T cells also showed an increase in cytolytic effector molecules. Apart from increased level of Granzyme A and Granzyme B, IL-15 cultured T cells exhibit increased accumulation of reactive oxygen (ROS) and reactive nitrogen (RNS) species as compared to IL-2 cultured T cells. Overall, this study suggests that T cells cultured in IL-15 show increase persistence not only due to increased anti-apoptotic proteins but also due to increased anti-oxidant levels, which is further complimented by increased cytolytic effector functions

GITR expression on T-cell receptor-stimulated human CD8+ T cell in a JNK-dependent pathway

Glucocorticoid-induced tumor necrosis factor receptor (TNFR) (GITR) family-related gene is a member of the TNFR super family. GITR works as one of the immunoregulatory molecule on CD4+ regulatory T cells and has an important role on cell survival or cell death in CD4+ T cells. Little is known about the expression of GITR on human CD8+ T cells on antigen-specific and non-specific activation. Here, we report that expression of GITR on human CD8+ T cells on T-cell receptor (TCR) (anti-CD3)-mediated stimulation is dependent on the JNK pathway. The activation of CD8+ T cells was measured by the expression of IL-2 receptor-α (CD25), GITR and by IFN-γ production upon re-stimulation with anti-CD3 antibody. We studied the signaling pathway of such inducible expression of GITR on CD8+ T cells. We found that a known JNK-specific inhibitor, SP600125, significantly down-regulates GITR expression on anti-CD3 antibody-mediated activated CD8+ T cells by limiting JNK phosphorylation. Subsequently, after stimulation of the CD8+ cells, we tested for the production of IFN-γ by the activated cells following restimulation with the same stimulus. It appears that the expression of GITR on activated human CD8+ T cells might also be regulated through the JNK pathway when the activation is through TCR stimulation. Therefore, GITR serves as an activation marker on activated CD8+ cells and interference with JNK phosphorylation, partially or completely, by varying the doses of SP600125 might have implications in CD8+ cytotoxic T cell response in translational research