Cell-dependent Mechanism Research Articles

Antibodies Contribute to Effective Vaccination against Respiratory Infection by Type A Francisella tularensis Strains

Pneumonic tularemia is a life-threatening disease caused by inhalation of the highly infectious intracellular bacterium Francisella tularensis. The most serious form of the disease associated with the type A strains can be prevented in experimental animals through vaccination with the attenuated live vaccine strain (LVS). The protection is largely cell mediated, but the contribution of antibodies remains controversial. We addressed this issue in a series of passive immunization studies in Fischer 344 (F344) rats. Subcutaneous LVS vaccination induced a robust serum antibody response dominated by IgM, IgG2a, and IgG2b antibodies. Prophylactic administration of LVS immune serum or purified immune IgG reduced the severity and duration of disease in naïve rats challenged intratracheally with a lethal dose of the virulent type A strain SCHU S4. The level of resistance increased with the volume of immune serum given, but the maximum survivable SCHU S4 challenge dose was at least 100-fold lower than that shown for LVS-vaccinated rats. Protection correlated with reduced systemic bacterial growth, less severe histopathology in the liver and spleen during the early phase of infection, and bacterial clearance by a T cell-dependent mechanism. Our results suggest that treatment with immune serum limited the sequelae associated with infection, thereby enabling a sterilizing T cell response to develop and resolve the infection. Thus, antibodies induced by LVS vaccination may contribute to the defense of F344 rats against respiratory infection by type A strains of F. tularensis.

Oral ingestion of Lentinula edodes mycelia extract inhibits B16 melanoma growth via mitigation of regulatory T cell‐mediated immunosuppression

Mitigation of regulatory T cell-mediated immunosuppression is crucial for optimal in vivo anti-tumor immune responses. In this study, we examined the anti-tumor effect induced by oral ingestion of an immunomodulating diet comprised of Lentinula edodes mycelia (L.E.M.) extract. C57BL/6 mice were inoculated subcutaneously in the footpad with B16 melanoma and fed L.E.M. extract. Ingestion of L.E.M. extract significantly inhibited tumor growth, and this in vivo anti-tumor effect was not observed in nude mice, suggesting a T cell-dependent mechanism. In addition, ingestion of L.E.M. extract led to significant restoration of H-2K(b) -restricted and melanoma-reactive T cells in the spleen and draining lymph nodes of melanoma-bearing mice. Flow cytometry analysis revealed that the percentage of Foxp3(+) CD4(+) T cells increased in spleen and draining lymph nodes in melanoma-bearing mice, but decreased significantly with ingestion of L.E.M. extract. Importantly, selective depletion of CD8(+) T cells abolished the L.E.M.-induced anti-tumor effect, whereas that of CD4(+) T cells or CD25(+) cells showed no additive influence on the effect. Real-time PCR analysis revealed that ingestion of L.E.M. extract by melanoma-bearing mice decreased the level of Foxp3 mRNA within the tumor tissues, and lowered plasma transforming growth factor (TGF)-β. Furthermore, an in vitro assay revealed that an immunosuppressive activity of CD4(+) T cells from melanoma-bearing mice was canceled by ingestion of L.E.M. extract. Our results indicate that oral ingestion of L.E.M. extract restores immune responses of class I-restricted and melanoma-reactive CD8(+) T cells in melanoma-bearing mice, presumably by a mitigation of regulatory T cells-mediated immunosuppression.

Angiogenic and lymphangiogenic cascades in the tumor microenvironment

Blood and lymphatic vessels in tumor tissue are major components of the tumor microenvironment. These vessels are newly formed from pre-existing host vessels stimulated by pro-blood-angiogenic and pro-lymph-angiogenic (pro-blood/lymph-angiogenic) factors expressed in tumor cells. Tumor cells establish a specific stromal microenvironment fostering tumor growth, in which blood/lymph-angiogenesis are involved. The tumor-associated blood/lymph-angiogenesis is continually induced by complicated cytokine networks, namely pro-blood/lymph-angiogenic factor-mediated paracrine and autocrine interactions among tumor cells and stromal cells including endothelial cells (ECs) and non-endothelial mesenchymal cells (neMCs). In this review, we provide an overview of the features of tumor-associated blood/lymph-angiogenesis based on recent and updated information obtained mainly from our studies. With regard to the constituent cell-dependent molecular mechanisms that regulate tumor blood/lymph-angiogenesis, we focus on: 1) the role of blood/lymph-angiogenesis-related factors/receptors expressed in tumor cells; and 2) the role of blood/lymph-angiogenesis-related factors/receptors expressed in stromal cells (ECs and neMCs). Finally, we discuss the features of tumor-associated blood/lymph-anigogenesis, especially a vessel abnormality through the viewpoint of blood/lymph-angiogenic cascades in tumor microenvironment for better understanding of the tumor vascular biology.

CD4+ and CD8+ T cell- and IL-17-mediated protection against Entamoeba histolytica induced by a recombinant vaccine

Amebiasis in the murine model can be prevented by vaccination with the Gal/GalNAc lectin through a T cell-dependent mechanism. In this work we further decipher the mechanism of this protection. Mice vaccinated with the recombinant “LecA” fragment of the Gal/GalNAc lectin with alum were capable of transferring protection to naïve recipients by both CD4+ T cells and surprisingly CD8+ T cells. We then examined the cytokine profile of these cells. CD4+ T cells from PBMC of LecA-alum vaccinated mice were observed to be a major source of IFN-γ, known to be a protective cytokine with this vaccine. In contrast, CD8+ T cells produced relatively little IFN-γ but more IL-17 than the CD4 compartment. We thus examined the role of IL-17 in vaccine mediated protection and found through neutralization experiments that this cytokine contributed to LecA-alum vaccine protection. In addition we examined whether these cells exhibited direct amebicidal activity in vitro and found that both populations had amebicidal activity at high concentrations (1000:1) but CD8+ T cells appeared more potent, capable of cytotoxicity at a 100:1 ratio. In conclusion, both CD4 and CD8 T cells exert protection with this amebiasis vaccine. The mechanism of CD8 T cell-mediated protection may include direct amebicidal activity and/or IL-17 production. Both IL-17 and IFN-γ are useful surrogates for immune protection.

LH-Induced Neuregulin 1 (NRG1) Type III Transcripts Control Granulosa Cell Differentiation and Oocyte Maturation

Epidermal growth factor (EGF)-like factors [amphiregulin (AREG), betacellulin, and epiregulin] are induced by LH and activate the EGF receptor (ERBB1)/ERK1/2 pathway in granulosa cells and cumulus cells of preovulatory follicles to impact ovulation. However, the expression and roles of other ERBB family members and their ligands have not been explored in detail. Herein, we document that two transcripts of the neuregulin (Nrg1) gene are expressed in granulosa cells, and that the type III Nrg1 is induced during ovulation in an ERK1/2 and C/EBPβ-dependent manner. Western blotting shows that intact (75 kDa) and secreted (45 kDa) forms of neuregulin 1 (NRG1) are present in the ovary. NRG1 likely binds to ERBB3/ERBB2 complexes that are expressed in granulosa cells and cumulus cells. In cultured granulosa cells, NRG1 selectively stimulates the phosphorylation of AKT/PKB compared to ERK1/2. However, when granulosa cells were cultured with NRG1 and AREG, the phosphorylation of ERK1/2 was markedly enhanced as compared with that by AREG alone. Cotreatment with NRG1 and AREG also increased progesterone production. When cumulus-oocyte complexes (COCs) were cultured with both NRG1 and AREG, the matured oocytes exhibited significantly higher developmental competence as compared with that of oocytes cultured with AREG alone. Collectively, these results document that the expression of type III NRG1 is induced in granulosa cells during ovulation and that NRG1 enhances AREG-induced ERK1/2 phosphorylation in both granulosa cells and cumulus cells. The NRG1 pathway has two roles: one is to enhance AREG-induced progesterone production in granulosa cells, and the other is to regulate oocyte maturation by a cumulus cell-dependent mechanism.

Inhibition of T cell–dependent and RANKL‐dependent osteoclastogenic processes associated with high levels of bone mass in interleukin‐15 receptor–deficient mice

T cell production of RANKL, interferon-γ (IFNγ), and other cytokines in inflammatory processes such as rheumatoid arthritis or secondary to conditions such as estrogen deficiency stimulates osteoclast activity, which leads to bone resorption and bone loss. The purpose of this study was to characterize the effects of interleukin-15 (IL-15), a master T cell growth factor whose role in bone remodeling remains unknown. We used mice lacking the IL-15 receptor (IL-15Rα(-/-) ) to investigate the effects of IL-15 on osteoclast development, T cell and dendritic cell activation in vitro and in vivo, bone mass, and microarchitecture in intact and ovariectomized (OVX) mice. In wild-type (WT) animals, IL-15 and RANKL provided a costimulatory signal for osteoclast development. Spleens from IL-15Rα(-/-) mice contained few c-Kit+ osteoclast precursors, and the expression of NF-ATc1 and the osteoclastogenic response to RANKL were impaired. In addition, dendritic cell-dependent and T cell-dependent mechanisms of osteoclast activation, including RANKL and IFNγ production, were impaired in IL-15Rα(-/-) mice. In turn, IL-15Rα(-/-) T cells failed to stimulate WT osteoclasts, whereas WT T cells failed to stimulate IL-15Rα(-/-) osteoclasts. Compared with WT mice, both intact and OVX IL-15Rα(-/-) mice had significantly greater bone mineral density and microarchitecture, including a higher trabecular bone volume fraction and cortical thickness. The numbers of osteoclasts on the bone surface as well as markers of bone turnover were significantly decreased in IL-15Rα(-/-) mice. In the absence of IL-15 signaling, several converging mechanisms of osteoclastogenesis are inhibited, both directly and indirectly, through T cells, which leads to a high bone mass phenotype. Targeting the IL-15 pathway may represent a novel therapeutic approach to treating primary and secondary osteoporosis.

NK cells suppress experimental cholestatic liver injury by an interleukin-6-mediated, Kupffer cell-dependent mechanism

Natural killer (NK) cells are innate immune effector cells first characterized by their ability to lyse susceptible tumor cells. Recent studies demonstrated their role in initiating and modulating adaptive immunity. NK cells represent a larger percentage of the lymphoid population in liver than other organs, suggesting that hepatic NK cells express some unique function. Here, we examined the response of NK cells to liver injury that occurs in a mouse model of biliary obstruction. Bile duct ligations (BDL) were performed in mice previously depleted or not depleted of NK cells. NK cell activation, interleukin (IL)-6 mRNA expression and protein production by Kupffer cells, and the ability of exogenous IL-6 to ameliorate liver injury in NK cell-depleted mice, were determined. The number of activated hepatic NK cells increased markedly following BDL. Activation was suppressed in mice rendered Kupffer cell-depleted prior to ligation. Increased liver injury occurred in NK cell-depleted mice correlating with a reduction in IL-6 production. Purified Kupffer cells, obtained from NK cell-depleted or anti-interferon (IFN)-γ monoclonal antibody-pretreated mice following BDL, produced less IL-6 in culture than did Kupffer cells derived from control animals. In culture, hepatic NK cells derived from BDL mice stimulated IFN-γ-dependent IL-6 production by Kupffer cells; splenic NK cells obtained from the same animals had a negligible effect. Treatment with recombinant murine IL-6 reduced liver injury in BDL, NK cell-depleted mice. Hepatic NK cells suppress cholestatic liver injury by stimulating Kupffer cell-dependent IL-6 production.

Inhibition of T Cells Provides Protection against Early Invasive Pneumococcal Disease

Infections caused by Streptococcus pneumoniae are major causes of morbidity and mortality, which are in part mediated by immune cell-dependent mechanisms. Yet, the specific contributions of individual cell types to immunopathology are only partially understood. T cells are well characterized with respect to their function in protective humoral immune responses; however, their roles during early stages of infection and invasive pneumococcal disease (IPD) are less well defined. Using a mouse model of pneumococcal sepsis, we found that CD4(+) T cells were recruited to the lung as early as 12 h after intranasal infection. Recruitment was accompanied by upregulation of CD69 and B7-H1, reflecting T-cell activation. Unexpectedly, major histocompatibility complex (MHC) class II-deficient mice, which lack CD4(+) T cells, displayed an increased survival despite comparable bacterial titers in the blood, spleen, and lung. The higher survival correlated with a lower cytokine and chemokine response upon S. pneumoniae challenge in MHC class II-deficient mice, suggesting that inflammation may contribute to the mortality of IPD. Comparable to the case for MHC class II-deficient mice, antibody-mediated depletion of CD4(+) T cells and drug-induced inhibition of T-cell function with cyclosporine, or interference with T-cell activation using CTLA4-immunoglobulin (Abatacept), led to significant increases in survival during IPD. Our results reveal an important and adverse role of CD4(+) T cells in the pathogenesis of IPD and suggest that modulation of T-cell activation during early phases of S. pneumoniae invasive infection may provide a therapeutic option.

Lack of acetylcholine nicotine alpha 7 receptor suppresses development of collagen-induced arthritis and adaptive immunity

Activation of the alpha7 receptor (α7nAChR) has been shown to be important in inflammation and immune regulation, and is also essential in the neural cholinergic anti-inflammatory pathway. The aim of this study was to investigate the role of α7nAChR in the development of experimental arthritis and immune activation. Mice lacking the α7nAChR were immunized with collagen II and the development of arthritis was assessed. Another group of α7nAChR-deficient mice was immunized with ovalbumin, spleen and lymph node cells were isolated and the proliferative responses to restimulation with ovalbumin or concanavalin A were investigated. We could demonstrate significantly milder arthritis and less cartilage destruction, together with a decrease of T cell content in lymph nodes in mice lacking the α7nAChR compared to wild-type controls. In addition, mice lacking the α7nAChR had a deficient proliferative response to concanavalin A, whereas antigen presentation-dependent proliferation was not affected. These results indicate important roles for α7nAChR in arthritis development as well as in regulation of T cell-dependent immunological mechanisms. In addition, the data implicate α7nAChR as a therapeutic target for modulation of adaptive immune responses.

Human monocytic cells direct the robust release of CXCL10 by bronchial epithelial cells during rhinovirus infection

Human rhinovirus (HRV) infections are a major cause of exacerbations in chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease, but HRV-induced immune responses of the lower airway are poorly understood. Earlier work examining cytokine release following HRV infection has focused on epithelial cells because they serve as the principal site of viral replication, and internalization and replication of viral RNA appear necessary for epithelial cell mediator release. However, during HRV infection, only a small proportion of epithelial cells become infected. As HRV-induced cytokine levels in vivo are markedly elevated, this observation suggests that other mechanisms independent of direct viral infection may induce epithelial cell cytokine release. Our aim was to test for the importance of interactions between human bronchial epithelial cells (HBECs) and monocytic cells in the control of mediator release during HRV exposure. In vitro models of HRV serotype-16 (HRV16) infection of primary HBECs and human monocytic cells, in mono or co-culture, were used. We assessed HRV16-induced CXCL10 and CCL2 protein release via ELISA. Co-culture of human monocytic and bronchial epithelial cells promoted a synergistic augmentation of CXCL10 and CCL2 protein release following HRV16 challenge. Transfer of conditioned media from HRV16-treated monocytic cells to epithelial cultures induced a robust release of CXCL10 by the epithelial cells. This effect was greatly attenuated by type I IFN receptor blocking antibodies, and could be recapitulated by IFN-alpha addition. Our data indicate that epithelial CXCL10 release during HRV infection is augmented by a monocytic cell-dependent mechanism involving type I IFN(s). Our findings support a key role for monocytic cells in the amplification of epithelial cell chemokine production during HRV infection, and help to explain how an inflammatory milieu is created in the lower airways even in the absence of extensive viral replication and epithelial infection.

MYC Inactivation Elicits Oncogene Addiction through Both Tumor Cell-Intrinsic and Host-Dependent Mechanisms

Tumorigenesis is generally caused by genetic changes that activate oncogenes or inactivate tumor suppressor genes. The targeted inactivation of oncogenes can be associated with tumor regression through the phenomenon of oncogene addiction. One of the most common oncogenic events in human cancer is the activation of the MYC oncogene. The inactivation of MYC may be a general and effective therapy for human cancer. Indeed, it has been experimentally shown that the inactivation of MYC can result in dramatic and sustained tumor regression in lymphoma, leukemia, osteosarcoma, hepatocellular carcinoma, squamous carcinoma, and pancreatic carcinoma through a multitude of mechanisms, including proliferative arrest, terminal differentiation, cellular senescence, induction of apoptosis, and the shutdown of angiogenesis. Cell-autonomous and cell-dependent mechanisms have both been implicated, and recent results suggest a critical role for autocrine factors, including thrombospondin-1 and TGF-β. Hence, targeting the inactivation of MYC appears to elicit oncogene addiction and, thereby, tumor regression through both tumor cell-intrinsic and host-dependent mechanisms.

Blood Fluke Exploitation of Non-Cognate CD4+ T Cell Help to Facilitate Parasite Development

Schistosoma blood flukes, which infect over 200 million people globally, co-opt CD4+ T cell-dependent mechanisms to facilitate parasite development and egg excretion. The latter requires Th2 responses, while the mechanism underpinning the former has remained obscure. Using mice that are either defective in T cell receptor (TCR) signaling or that lack TCRs that can respond to schistosomes, we show that naïve CD4+ T cells facilitate schistosome development in the absence of T cell receptor signaling. Concurrently, the presence of naïve CD4+ T cells correlates with both steady-state changes in the expression of genes that are critical for the development of monocytes and macrophages and with significant changes in the composition of peripheral mononuclear phagocyte populations. Finally, we show that direct stimulation of the mononuclear phagocyte system restores blood fluke development in the absence of CD4+ T cells. Thus we conclude that schistosomes co-opt innate immune signals to facilitate their development and that the role of CD4+ T cells in this process may be limited to the provision of non-cognate help for mononuclear phagocyte function. Our findings have significance for understanding interactions between schistosomiasis and other co-infections, such as bacterial infections and human immunodeficiency virus infection, which potently stimulate innate responses or interfere with T cell help, respectively. An understanding of immunological factors that either promote or inhibit schistosome development may be valuable in guiding the development of efficacious new therapies and vaccines for schistosomiasis.

Abstract 2412: Sorafenib can be effectively combined with GM-CSF secreting cellular immunotherapy in a mouse model of HER-2+ breast cancer

Abstract Due to the complexities of the tumor microenvironment and the frequent emergence of drug resistance with treatment, it is increasingly evident that cancer therapy will have to hit multiple host and tumor targets simultaneously. We previously reported that DC101, an antiangiogenic monoclonal antibody specific for the vascular endothelial growth factor receptor-2 (VEGFR-2), can enhance tumor immunity by a T cell-dependent mechanism. Sorafenib, a small molecule that also disrupts angiogenesis, blocks signaling through multiple kinases that control tumor growth and progression. It has also been reported to inhibit both dendritic cell (DC) and T cell function. To further explore the intrinsic tumor- and host-based effects of sorafenib, we tested it against murine HER-2+ breast tumor cells (NT) in vitro, and in NT-tumor-bearing FVB/N (immune-competent) and neu-N (immune tolerant to HER-2) mice in vivo. Sorafenib inhibited the growth of NT tumor cells in vitro, inducing apoptosis. Western blot analysis revealed that Sorafenib interfered with ERK/MAPK, but not AKT, signaling pathways, both of which are constitutively activated when HER-2 is over-expressed. Single agent sorafenib effectively controlled the growth of established tumors in immune competent FVB/N mice, but did not result in complete tumor clearance. In contrast, sorafenib alone did not significantly impact the outgrowth of established tumors in neu-N mice, where tumor-specific immune tolerance is in play. Consistent with this observation, depletion studies conducted in immune competent FVB/N mice revealed that the control of tumor growth is in part dependent on T cells, but not macrophages or NK cells. While sorafenib treatment alone did not induce immunity specific for RNEU420–429 (the immunodominant HER-2 epitope), it did accelerate tumor clearance induced by vaccination with a granulocyte-macrophage colony-simulating factor (GM-CSF)-secreting, HER-2+ cellular vaccine in tumor-bearing FVB/N mice compared to either drug treatment or vaccination alone. Finally, sorafenib neither augmented nor inhibited the vaccine-induced T cell response specific for RNEU420–429 as measured by ELISPOT and intracellular cytokine staining. Overall, these findings suggest that vaccine-based immunotherapy can interact with kinase inhibitors by distinct mechanisms for enhanced therapeutic response. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2412.

Antibody can mediate protective immunity at early tissue-dwelling stages of intestinal helminth infection (37.27)

Abstract B cells may be critical in mediating protective immunity by aiding Th2 cell development and/or antibody production. To examine the role of B cells during helminth infection B cell-deficient mice were inoculated with one of two intestinal nematode parasites: Nippostrongylus brasiliensis (Nb) and Heligmosomoides polygyrus (Hp). A similar pattern in elevation of Th2 cytokine gene expression was seen in B cell-deficient and WT mice after inoculation with either species. No difference in worm expulsion was found between B cell-deficient and WT mice after Nb infection, but differences in worm expulsion occurred after Hp inoculation. At day 4 and day 7 after secondary Hp challenge impaired larval migration and development occurred in WT but not B cell-deficient mice suggesting that both early invasion and in situ larval development were inhibited through B cell-dependent mechanisms. Administration of immune serum to B cell-deficient mice restored protective immunity and when given to naïve mice mediated protective effects, suggesting a primary role for antibody in protective immunity during Hp infection. Thus, these data indicate that B cells contribute to protective immunity during Th2-types responses primarily through their production of antibodies and that their importance varies among different species of intestinal helminthes.

T cells can mediate viral clearance from ependyma but not from brain parenchyma in a major histocompatibility class I- and perforin-independent manner

Viral infection of the central nervous system can lead to disability and death. Yet the majority of viral infections with central nervous system involvement resolve with only mild clinical manifestations, if any. This is generally attributed to efficient elimination of the infection from the brain coverings, i.e. the meninges, ependyma and chorioplexus, which are the primary targets of haematogeneous viral spread. How the immune system is able to purge these structures from viral infection with only minimal detrimental effects is still poorly understood. In the present work we studied how an attenuated lymphocytic choriomeningitis virus can be cleared from the central nervous system in the absence of overt disease. We show that elimination of the virus from brain ependyma, but not from brain parenchyma, could be achieved by a T cell-dependent mechanism operating independently of major histocompatibility class I antigens and perforin. Considering that cytotoxic T lymphocyte-mediated cytotoxicity is a leading cause of viral immunopathology and tissue damage, our findings may explain why the most common viral intruders of the central nervous system rarely represent a serious threat to our health.

Recombinant TCR ligand reverses clinical signs and CNS damage of EAE induced by recombinant human MOG.

Increasing evidence suggests that in addition to T cell-dependent effector mechanisms, autoantibodies are also involved in the pathogenesis of MS, including demyelinating antibodies specific for myelin oligodendrocyte glycoprotein (MOG). Our previous studies have demonstrated that recombinant T cell receptor ligands (RTLs) are very effective for treating T cell-mediated experimental autoimmune encephalomyelitis (EAE). In order to expand the scope of RTL therapy in MS patients, it was of interest to study RTL treatment of EAE involving a demyelinating antibody component. Therefore, we evaluated the therapeutic effects of RTL551, specific for T cells reactive to mouse (m)MOG-35-55 peptide, on EAE induced with recombinant human (rh)MOG in C57BL/6 mice. We report that RTL551 therapy can reverse disease progression and reduce demyelination and axonal damage induced by rhMOG without suppressing the anti-MOG antibody response. This result suggests that T cell-mediated inflammation and associated blood-brain barrier dysfunction are the central contributors to EAE pathogenesis and that successful regulation of these key players restricts potential damage by demyelinating antibodies. The results of our study lend support for the use of RTL therapy for treatment of MS subjects whose disease includes inflammatory T cells as well as those with an additional antibody component.

Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 Modulates Experimental Autoimmune Encephalomyelitis via an iNKT Cell-Dependent Mechanism

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a CEA family member that has been reported to have an important role in the regulation of Th1-mediated colitis. In this study, we examined the role of CEACAM1 in an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Treatment of C57BL/6J mice with CEACAM1-Fc fusion protein, a homophilic ligand of CEACAM1, inhibited the severity of EAE and reduced myelin oligodendrocyte glycoprotein-derived peptide (MOG(35-55))-reactive interferon-gamma and interleukin-17 production. In contrast, treatment of these animals with AgB10, an anti-mouse CEACAM1 blocking monoclonal antibody, generated increased severity of EAE in association with increased MOG(35-55)-specific induction of both interferon-gamma and interleukin-17. These results indicated that the signal elicited through CEACAM1 ameliorated EAE disease severity. Furthermore, we found that there was both a rapid and enhanced expression of CEACAM1 on invariant natural killer T cells after activation. The effect of CEACAM1-Fc fusion protein and anti-CEACAM1 mAb on both EAE and MOG(35-55)-reactive cytokine responses were abolished in invariant natural killer T cell-deficient Jalpha18(-/-) mice. Taken together, the ligation of CEACAM1 negatively regulates the severity of EAE by reducing MOG(35-55)-specific induction of both interferon-gamma and interleukin-17 via invariant natural killer T cell-dependent mechanisms.

Cervical Cancer-Associated Human Papillomavirus 16 E7 Oncoprotein Inhibits Induction of Anti-Cancer Immunity by a CD4+ T Cell Dependent Mechanism

AbstractAttempts to develop therapeutic vaccines against cervical cancer have been proven difficult. One of the major causes of the failure is due to the use of the wrong mouse models based on transplantable tumours in testing the efficacy of vaccines. Now that a transgenic epithelial mouse model has been developed to closely mimic cervical cancer, the mechanisms needed to eliminate this type of cancer could be studied. The E7 oncoprotein of Human Papillomavirus (HPV) is the most expressed HPV protein in cervical cancers and its continuous production is essential to maintain the cancerous state and therefore the obvious target in the development of vaccines. Skin grafts expressing the HPV 16 E7 protein (E7 autografts) are not spontaneously rejected from an MHC matched immunocompetent host. Interestingly, simultaneous placement of an MHC mismatched skin (allograft) next to an E7 autograft results in the E7 autograft rejection. However when the allograft also expresses E7, the E7 autograft is rejected more slowly. Autograft rejection requires CD8+ T cells, and is accelerated by removal of CD4+ T cells after placement of the E7 expressing allograft, suggesting induction of an E7 specific CD4+ regulatory T cell population by the E7 expressing allograft. This observation may have implications in designing effective vaccines and immunotherapy against cervical cancers in women.

Cervical Cancer-Associated Human Papillomavirus 16 E7 Oncoprotein Inhibits Induction of Anti-Cancer Immunity by a CD4+ T Cell Dependent Mechanism

Cervical Cancer-Associated Human Papillomavirus 16 E7 Oncoprotein Inhibits Induction of Anti-Cancer Immunity by a CD4+ T Cell Dependent Mechanism

Keratinocyte Growth Factor Improves Allogeneic Bone Marrow Engraftment through a CD4+Foxp3+ Regulatory T Cell-Dependent Mechanism

Keratinocyte growth factor (KGF) protects mice from acute graft-vs-host disease and graft rejection by cytoprotective and yet incompletely understood immunological mechanisms. Recently, we showed that administration of KGF induces selective peripheral expansion of CD4(+)Foxp3(+) regulatory T cells (Treg). In this study, we set out to assess whether the peripheral expansion of Treg accounts for the immunomodulatory effects of KGF after bone marrow (BM) transplantation. To exclude potentially confounding cytoprotective and thymopoietic effects of KGF, we applied KGF to congenic wild-type mice that served as T cell provider mice for T and B cell-deficient RAG-1(-/-) mice that were subsequently transplanted with allogeneic BM. Treatment of congenic T cell provider mice with KGF significantly improved engraftment and reduced graft rejection in BMT recipients. CD4(+)Foxp3(+) Treg remained increased for 4 wk, while expansion of congenic CD3(+) T cells was inhibited. To assess a causal relationship between expansion of Treg and improved BM engraftment, congenic Scurfy mice, which lack Foxp3(+) Treg, served as T cell provider mice and were treated with KGF. KGF-treatment of Scurfy mice did not affect engraftment nor did it inhibit the expansion of congenic T cells. These data demonstrate that administration of KGF to the T cell provider mice improves engraftment of allogeneic BM through a CD4(+)Foxp3(+) Treg-dependent mechanism.