Interferon γ (IFN-γ) Is Necessary for the Genesis of Acetylcholine Receptor–induced Clinical Experimental Autoimmune Myasthenia gravis in Mice

Experimental autoimmune myasthenia gravis (EAMG) is an animal model of human myasthenia gravis (MG). In mice, EAMG is induced by immunization with Torpedo californica acetylcholine receptor (AChR) in complete Freund's adjuvant (CFA). However, the role of cytokines in the pathogenesis of EAMG is not clear. Because EAMG is an antibody-mediated disease, it is of the prevailing notion that Th2 but not Th1 cytokines play a role in the pathogenesis of this disease. To test the hypothesis that the Th1 cytokine, interferon (IFN)-γ, plays a role in the development of EAMG, we immunized IFN-γ knockout (IFN-gko) (−/−) mice and wild-type (WT) (+/+) mice of H-2b haplotype with AChR in CFA. We observed that AChR-primed lymph node cells from IFN-gko mice proliferated normally to AChR and to its dominant pathogenic α146–162 sequence when compared with these cells from the WT mice. However, the IFN-gko mice had no signs of muscle weakness and remained resistant to clinical EAMG at a time when the WT mice exhibited severe muscle weakness and some died. The resistance of IFN-gko mice was associated with greatly reduced levels of circulating anti-AChR antibody levels compared with those in the WT mice. Comparatively, immune sera from IFN-gko mice showed a dramatic reduction in mouse AChR-specific IgG1 and IgG2a antibodies. However, keyhole limpet hemocyanin (KLH)–priming of IFN-gko mice readily elicited both T cell and antibody responses, suggesting that IFN-γ regulates the humoral immune response distinctly to self (AChR) versus foreign (KLH) antigens. We conclude that IFN-γ is required for the generation of a pathogenic anti-AChR humoral immune response and for conferring susceptibility of mice to clinical EAMG

The roles of mast cells in anticancer immunity

The tumor microenvironment (TME), which is composed of stromal cells such as endothelial cells, fibroblasts, and immune cells, provides a supportive niche promoting the growth and invasion of tumors. The TME also raises an immunosuppressive barrier to effective antitumor immune responses and is therefore emerging as a target for cancer immunotherapies. Mast cells (MCs) accumulate in the TME at early stages, and their presence in the TME is associated with poor prognosis in many aggressive human cancers. Some well-established roles of MCs in cancer are promoting angiogenesis and tumor invasion into surrounding tissues. Several mouse models of inducible and spontaneous cancer show that MCs are among the first immune cells to accumulate within and shape the TME. Although MCs and other suppressive myeloid cells are associated with poor prognosis in human cancers, high densities of intratumoral T effector (T(eff)) cells are associated with a favorable prognosis. The latter finding has stimulated interest in developing therapies to increase intratumoral T cell density. However, cellular and molecular mechanisms promoting high densities of intra-tumoral T(eff) cells within the TME are poorly understood. New evidence suggests that MCs are essential for shaping the immune-suppressive TME and impairing both antitumor T(eff) cell responses and intratumoral T cell accumulation. These roles for MCs warrant further elucidation in order to improve antitumor immunity. Here, we will summarize clinical studies of the prognostic significance of MCs within the TME in human cancers, as well as studies in mouse models of cancer that reveal how MCs are recruited to the TME and how MCs facilitate tumor growth. Also, we will summarize our recent studies indicating that MCs impair generation of protective antitumor T cell responses and accumulation of intratumoral T(eff) cells. We will also highlight some approaches to target MCs in the TME in order to unleash antitumor cytotoxicity

Adjuvant Immunotherapy of Experimental Autoimmune Encephalomyelitis: Immature Myeloid Cells Expressing CXCL10 and CXCL16 Attract CXCR3(+)CXCR6(+) and Myelin-Specific T Cells to the Draining Lymph Nodes Rather Than the Central Nervous System

CFA is a strong adjuvant capable of stimulating cellular immune responses. Paradoxically, adjuvant immunotherapy by prior exposure to CFA or live mycobacteria suppresses the severity of EAE and spontaneous diabetes in rodents. Here we investigated immune responses during adjuvant immunotherapy of experimental autoimmune encephalomyelitis (EAE). Induction of EAE in CFA-pretreated mice resulted in a rapid influx into the draining lymph nodes (dLNs) of large numbers of CD11b(+)Gr-1(+) myeloid cells, consisting of immature cells with ring-shaped nuclei, macrophages, and neutrophils. Concurrently, a population of mycobacteria-specific IFN-γ-producing T cells appeared in the dLNs. Immature myeloid cells in dLNs expressed the chemokines CXCL10 and CXCL16 in an IFN-γ-dependent manner. Subsequently, CD4(+) T cells co-expressing the cognate chemokine receptors, CXCR3 and CXCR6, and myelin oligodendrocyte glycoprotein (MOG)-specific CD4(+) T cells accumulated within the chemokine-expressing dLNs, rather than within the CNS. Migration of CD4(+) T cells toward dLN cells was abolished by depleting the CD11b(+) cells and was also mediated by the CD11b(+) cells alone. In addition to altering the distribution of MOG-specific T cells, adjuvant-treatment suppressed development of MOG-specific IL-17. Thus, CFA-adjuvant immunotherapy of EAE requires IFN-γ, which suppresses development of the Th17-response, and diverts autoreactive T cells away from the CNS towards immature myeloid cells expressing CXCL10 and CXCL16 in the lymph nodes

Mast cells impair the development of protective anti-tumor immunity

Mast cells have emerged as critical intermediaries in the regulation of peripheral tolerance. Their presence in many precancerous lesions and tumors is associated with a poor prognosis, suggesting mast cells may promote an immunosuppressive tumor microenvironment and impede the development of protective anti-tumor immunity. The studies presented herein investigate how mast cells influence tumor-specific T cell responses. Male MB49 tumor cells, expressing HY antigens, induce anti-tumor IFN-γ+ T cell responses in female mice. However, normal female mice cannot control progressive MB49 tumor growth. In contrast, mast cell-deficient c-Kit(Wsh) (W(sh)) female mice controlled tumor growth and exhibited enhanced survival. The role of mast cells in curtailing the development of protective immunity was shown by increased mortality in mast cell-reconstituted W(sh) mice with tumors. Confirmation of enhanced immunity in female W(sh) mice was provided by (1) higher frequency of tumor specific IFN-γ+ CD8+ T cells in tumor-draining lymph nodes compared with WT females and (2) significantly increased ratios of intratumoral CD4+ and CD8+ T effector cells relative to tumor cells in W(sh) mice compared to WT. These studies are the first to reveal that mast cells impair both regional adaptive immune responses and responses within the tumor microenvironment to diminish protective anti-tumor immunity

Adjuvant Immunotherapy of Experimental Autoimmune Encephalomyelitis: Immature Myeloid Cells Expressing CXCL10 and CXCL16 Attract CXCR3 +

CFA is a strong adjuvant capable of stimulating cellular immune responses. Paradoxically, adjuvant immunotherapy by prior exposure to CFA or live mycobacteria suppresses the severity of EAE and spontaneous diabetes in rodents. Here we investigated immune responses during adjuvant immunotherapy of experimental autoimmune encephalomyelitis (EAE). Induction of EAE in CFA-pretreated mice resulted in a rapid influx into the draining lymph nodes (dLNs) of large numbers of CD11b(+)Gr-1(+) myeloid cells, consisting of immature cells with ring-shaped nuclei, macrophages, and neutrophils. Concurrently, a population of mycobacteria-specific IFN-γ-producing T cells appeared in the dLNs. Immature myeloid cells in dLNs expressed the chemokines CXCL10 and CXCL16 in an IFN-γ-dependent manner. Subsequently, CD4(+) T cells co-expressing the cognate chemokine receptors, CXCR3 and CXCR6, and myelin oligodendrocyte glycoprotein (MOG)-specific CD4(+) T cells accumulated within the chemokine-expressing dLNs, rather than within the CNS. Migration of CD4(+) T cells toward dLN cells was abolished by depleting the CD11b(+) cells and was also mediated by the CD11b(+) cells alone. In addition to altering the distribution of MOG-specific T cells, adjuvant-treatment suppressed development of MOG-specific IL-17. Thus, CFA-adjuvant immunotherapy of EAE requires IFN-γ, which suppresses development of the Th17-response, and diverts autoreactive T cells away from the CNS towards immature myeloid cells expressing CXCL10 and CXCL16 in the lymph nodes

Disseminated tuberculosis in interferon gamma gene-disrupted mice.

The expression of protective immunity to Mycobacterium tuberculosis in mice is mediated by T lymphocytes that secrete cytokines. These molecules then mediate a variety of roles, including the activation of parasitized host macrophages, and the recruitment of other mononuclear phagocytes to the site of the infection in order to initiate granuloma formation. Among these cytokines, interferon gamma (IFN-gamma) is believed to play a key role is these events. In confirmation of this hypothesis, we show in this study that mice in which the IFN-gamma gene has been disrupted were unable to contain or control a normally sublethal dose of M. tuberculosis, delivered either intravenously or aerogenically. In such mice, a progressive and widespread tissue destruction and necrosis, associated with very high numbers of acid-fast bacilli, was observed. In contrast, despite the lack of protective immunity, some DTH-like reactivity could still be elicited. These data, therefore, indicate that although IFN-gamma may not be needed for DTH expression, it plays a pivotal and essential role in protective cellular immunity to tuberculosis infection