Complementary activation of peripheral natural killer cell immunity in nasopharyngeal carcinoma

NK cells and αβ- and γδ-CTL play important roles in cellular immunity against tumors. We previously demonstrated that NPC patients have a quantitative and qualitative deficit in γδ-CTL and EBV-specific αβ-CTL when compared to normal subjects and NPC long-term survivors. In this study we report further observations of a complementary activation of peripheral NK cells in NPC patients. The NK cells in these patients, compared to those of healthy subjects and NPC survivors, were preferentially activated in response to the stimulation of myeloma cell line XG-7 and expanded in the presence of exogenous IL-2. The production of IFN-γ was lowest in the patient group, whereas IL-12, IL-15 and TNF-α were produced in higher levels in patients than in the donors and survivors. The cytolytic effect of the NK cells against NPC cells in the patient group was also higher than that of the donors and survivors. Furthermore, the patients at later stages of NPC had lower γδ-CTL activity but higher NK cytotoxicity towards NPC targets, with higher production of IL-12, IL-15 and TNF-α but lower production of IFN-γ than in patients at earlier stages. This might be part of a triggered compensatory re-activation of the innate immunity, believed to be mediated through various cytokines and chemokines when adaptive T cell immunity is breached. Together, these data suggest complementary roles of innate and adaptive immune response in tumor immunity where NK cells, γδ- and αβ-CTL compensate for the deficits of one another at different stages of tumor invasion. © 2006 Japanese Cancer Association.published_or_final_versio

Conditional Stat1 Ablation Reveals the Importance of Interferon Signaling for Immunity to Listeria monocytogenes Infection

Signal transducer and activator of transcription 1 (Stat1) is a key player in responses to interferons (IFN). Mutations of Stat1 cause severe immune deficiencies in humans and mice. Here we investigate the importance of Stat1 signaling for the innate and secondary immune response to the intracellular bacterial pathogen Listeria monocytogenes (Lm). Cell type-restricted ablation of the Stat1 gene in naïve animals revealed unique roles in three cell types: macrophage Stat1 signaling protected against lethal Lm infection, whereas Stat1 ablation in dendritic cells (DC) did not affect survival. T lymphocyte Stat1 reduced survival. Type I IFN (IFN-I) signaling in T lymphocytes reportedly weakens innate resistance to Lm. Surprisingly, the effect of Stat1 signaling was much more pronounced, indicating a contribution of Stat1 to pathways other than the IFN-I pathway. In stark contrast, Stat1 activity in both DC and T cells contributed positively to secondary immune responses against Lm in immunized animals, while macrophage Stat1 was dispensable. Our findings provide the first genetic evidence that Stat1 signaling in different cell types produces antagonistic effects on innate protection against Lm that are obscured in mice with complete Stat1 deficiency. They further demonstrate a drastic change in the cell type-dependent Stat1 requirement for memory responses to Lm infection

Combinations of IFN-gamma and IL-4 Induce Distinct Profiles of Dendritic Cell Associated Immunoregulatory Properties

Interferon gamma (IFN-gamma) and interleukin-4 (IL-4) are not only generated during cell-mediated immunity (CMI) and humoral immunity (HI), but are also generated by innate immune cells in response to pathogenic factors. How these cytokines differentially effect the development of dendritic cell (DC)-associated immunoregulatory properties from progenitor cells during innate immunity is unresolved. To address this we have utilized a homogeneous DC progenitor-like cell line, MTHC-D2, as a model to examine cytokine-induced maturation of DCs. By 6 h IFN-gamma induced genes that are important for antiviral activity and development of CMI, whereas IL-4 induced genes involved in cellular adhesion, uptake of extracellular antigen, suppression of cytotoxic T-cell responses, and that repair the extracellular matrix. By 48 h the cytokine stimulus had induced many properties characteristic of immature DCs; however, these were differentially effected by IFN-gamma and IL-4. IFN-gamma induced the greatest levels of costimulatory/ activation marker expression, and the highest levels of T-cell proliferation, whereas IL-4 induced the greatest levels of phagocytic activity. Stimulation of the cells with CD40 Ab enhanced the levels of costimulatory marker expression and T-cell stimulatory capacity of cells exposed to IFN-gamma, but had little effect on cells exposed to IL-4 in the absence of IFN-gamma