The Role of the PD-1 Immunoreceptor in Pregnancy

During pregnancy, the maternal immune system must be carefully modulated as the fetus is immunologically foreign to her leukocytes. We propose that the CD28 family immune receptor, PD-1, functions during pregnancy to control maternal immune reactions. PD-1 is expressed on T lymphocytes and following interaction with its ligand, B7-H1, prevents T cell activation. B7-H1 is expressed in the human placenta throughout gestation, therefore we studied the role of the PD-1 receptor in modulating maternal T cells during pregnancy. PD-1 is preferentially expressed on human decidual T cells and B7-H1 inhibits the inflammatory cytokine production of activated decidual T lymphocytes. In addition, possibly through B7-H1:PD-1 interactions, trophoblasts induce regulatory T cell expansion in vitro. Finally, in murine pregnancy, PD-1 controls the accumulation of paternal antigen-specific T cells in the uterus-draining lymph nodes. Overall, these studies suggest that the PD-1:B7-H1 pathway functions to help maintain maternal-fetal tolerance

CNS Expression of B7-H1 Regulates Pro-Inflammatory Cytokine Production and Alters Severity of Theiler's Virus-Induced Demyelinating Disease

The CNS is a unique organ due to its limited capacity for immune surveillance. As macrophages of the CNS, microglia represent a population originally known for the ability to assist neuronal stability, are now appreciated for their role in initiating and regulating immune responses in the brain. Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease is a mouse model of multiple sclerosis (MS). In response to TMEV infection in vitro, microglia produce high levels of inflammatory cytokines and chemokines, and are efficient antigen-presenting cells (APCs) for activating CD4+ T cells. However, the regulatory function of microglia and other CNS-infiltrating APCs in response to TMEV in vivo remains unclear. Here we demonstrate that microglia increase expression of proliferating cell nuclear antigen (PCNA), and phenotypically express high levels of major histocompatibility complex (MHC)-Class I and II in response to acute infection with TMEV in SJL/J mice. Microglia increase expression of the inhibitory co-stimulatory molecule, B7-H1 as early as day 5 post-infection, while CNS-infiltrating CD11b+CD11c−CD45HIGH monocytes/macrophages and CD11b+CD11c+CD45HIGH dendritic cells upregulate expression of B7-H1 by day 3 post-infection. Utilizing a neutralizing antibody, we demonstrate that B7-H1 negatively regulates TMEV-specific ex vivo production of interferon (IFN)-γ, interleukin (IL)-17, IL-10, and IL-2 from CD4+ and CD8+ T cells. In vivo blockade of B7-H1 in SJL/J mice significantly exacerbates clinical disease symptoms during the chronic autoimmune stage of TMEV-IDD, but only has minimal effects on viral clearance. Collectively, these results suggest that CNS expression of B7-H1 regulates activation of TMEV-specific T cells, which affects protection against TMEV-IDD

Efficient Dendritic Cell Maturation and Initiation a Strong T Cell Immune Response Requires B7-H1-Mediated Dendritic Cell ‘Conditioning’ During Interaction with T Cells

One of the prominent features of the adaptive immune system is the extensive interactions between T cells and dendritic cells (DCs). The T cell-DC interactions are essential for T cell development, homeostasis, and activation, and require two signals, known as ‘The two signal model’. The first signal is initiated by T cell receptor (TCR) upon recognition of antigen in the form of peptides presented by the major histocompatibility complex (MHC) molecules. The second signal is mediated by engagement of co-regulatory molecules on naive T cells with its counterpart expressed by mature DCs. Depending on the nature of the regulatory signal both, DCs and T cells are affected. In this PhD work, we demonstrate the dual characteristics of the co-regulatory B7-H1 (PD-L1) molecules. B7-H1 expression in peripheral tissues such as the lung, during the peak of infection, negatively influenced antigen-specific T cell response and induced T cell apoptosis, most likely by binding to the inhibitory PD-1 receptor on T cells. This result suggests that inhibitory B7-H1:PD-1 interaction provides a mechanism to limit the excessive accumulation of effector T cells in the lung after the virus is cleared. More importantly, this study shows a novel stimulatory function of the B7-H1 molecules that are expressed on T cells in regulation of DC development and maturation. Flow cytometric analysis revealed that following WSN-SIY influenza infection, dendritic cell maturation in B7-H1-/- mice is defective and consequently CD8 T cell response is diminished. The adoptive transfer of B7-H1-expressing T cells however completely restored DC maturation in the draining lymphnode and enhanced CD8 T cell response, such as activation and proliferation. Moreover, maturation-defective DCs in T and B cell-deficient RAG-1 knock-out mice after influenza infection were also rescued by B7-H1+ T cells. Further analyses demonstrated the rescue of T cell response in B7-H1-/- mice by transfer of immature DCs from either B7-H1+/+ wild type mice or RAG-1-/- mice that had previously received B7-H1+ T cells. These findings illustrate the molecular requirement for T cell-dependent DC maturation and describe the cellular interactions that promote efficient T cell responses to microbial infection. It is essential that DCs acquire a B7-H1-mediated conditioned state during interaction with T cells before efficient DC maturation upon antigen-stimulation is enabled

Regulation of the B7-H1 (CD274) inhibitory molecule expression on tumour and immune cells.

Kostimulační/inhibiční molekuly rodiny B7, které jsou exprimovány na antigen prezentujících a dalších buňkách, včetně nádorových, hrají důležitou roli v regulaci imunitní odpovědi. Molekuly vazbou přes receptor ovlivňují aktivitu T-lymfocytů a to jak pozitivně, tak negativně. Mezi významné členy této rodiny patří molekula B7-H1 (CD274, PD-L1). Je exprimována v různých tkáních těla, nejen v buňkách hematopoetické řady. Význačná je i její prezentace na povrchu mnoha nádorových buněk. B7-H1 má dva vazebné receptory v cytoplazmatické membráně T-lymfocytů. Jeden receptor nebyl zatím určen, druhým receptorem je PD-1 (CD279) molekula. Vazba mezi B7-H1 - PD-1 negativně reguluje proliferaci, diferenciaci a produkci cytokinů T-lymfocyty, což je důležité při tvorbě periferní tolerance a zároveň při úniku nádorových buněk v proti-nádorové odpovědi tvořené T- lymfocyty. Přestože mechanismy regulace exprese B7-H1 na povrchu buněk byly v posledních letech intenzivně studovány, zvláště v případě nádorových buněk nejsou plně objasněny. Exprese B7-H1 je ovlivněna hlavně cytokiny IFNγ a TNFα jak na transkripční úrovni, tak na post-transkripční úrovni. V promotoru molekuly se nacházejí vazebná místa pro transkripční faktor IRF-1 a NF-κB. IRF-1 je aktivován působením IFNγ. NF-κB je aktivován samotným TNFα, samotným...The co-stimulatory/inhibitory molecules of family B7 that are expressed on the surface of antigen-presenting and other cells, including tumour cells, play an important role in immune responses regulations. Owing to binding on the T-lymphocyte receptors, they regulate their positive and also negative responses. An important co-stimulatory member of B7 family is B7-H1 molecule. This molecule is presented in many different tissues, not only on haematopoietic cells. However, it is also expressed on tumour cells. Its two binding receptors are in the cytoplasmic membrane of T-cells. The first receptor is unknown and the second receptor is PD-1 (CD279). The linkage between B7-H1 - PD-1 regulates negatively proliferation, differentiation and cytokine secretion of T-cells. This negative regulation is crucial for the constitution of peripheral immune tolerance and also for escape of tumour cells from T-lymphocyte based anti-tumour responses. Although the mechanisms underlying the B7-H1 cell-surface expression have been intensively studied, and they are not fully understood, especially in tumour cells. IFNγ and TNFα regulate B7-H1 expression on transcription level as well as on post- transcription level. Binding sites for transcription factors IRF-1 and NF-κB are located in B7- H1 promoter region. The IRF-1...Katedra buněčné biologieDepartment of Cell BiologyPřírodovědecká fakultaFaculty of Scienc

B7-H1 Blockade Increases Survival of Dysfunctional CD8+ T Cells and Confers Protection against Leishmania donovani Infections

Experimental visceral leishmaniasis (VL) represents an exquisite model to study CD8+ T cell responses in a context of chronic inflammation and antigen persistence, since it is characterized by chronic infection in the spleen and CD8+ T cells are required for the development of protective immunity. However, antigen-specific CD8+ T cell responses in VL have so far not been studied, due to the absence of any defined Leishmania-specific CD8+ T cell epitopes. In this study, transgenic Leishmania donovani parasites expressing ovalbumin were used to characterize the development, function, and fate of Leishmania-specific CD8+ T cell responses. Here we show that L. donovani parasites evade CD8+ T cell responses by limiting their expansion and inducing functional exhaustion and cell death. Dysfunctional CD8+ T cells could be partially rescued by in vivo B7-H1 blockade, which increased CD8+ T cell survival but failed to restore cytokine production. Nevertheless, B7-H1 blockade significantly reduced the splenic parasite burden. These findings could be exploited for the design of new strategies for immunotherapeutic interventions against VL

B7-H4 expression identifies a novel suppressive macrophage population in human ovarian carcinoma

Tumor-associated macrophages are a prominent component of ovarian cancer stroma and contribute to tumor progression. B7-H4 is a recently identified B7 family molecule. We show that primary ovarian tumor cells express intracellular B7-H4, whereas a fraction of tumor macrophages expresses surface B7-H4. B7-H4+ tumor macrophages, but not primary ovarian tumor cells, suppress tumor-associated antigen-specific T cell immunity. Blocking B7-H4-, but not arginase-, inducible nitric oxide synthase or B7-H1 restored the T cell stimulating capacity of the macrophages and contributes to tumor regression in vivo. Interleukin (IL)-6 and IL-10 are found in high concentrations in the tumor microenvironment. These cytokines stimulate macrophage B7-H4 expression. In contrast, granulocyte/macrophage colony-stimulating factor and IL-4, which are limited in the tumor microenvironment, inhibit B7-H4 expression. Ectopic expression of B7-H4 makes normal macrophages suppressive. Thus, B7-H4+ tumor macrophages constitute a novel suppressor cell population in ovarian cancer. B7-H4 expression represents a critical checkpoint in determining host responses to dysfunctional cytokines in ovarian cancer. Blocking B7-H4 or depleting B7-H4+ tumor macrophages may represent novel strategies to enhance T cell tumor immunity in cancer

Regulation of the expression of MHC class I molecules and other immunoactive molecules on tumor cells

4 Abstract Regulation of the expression of MHC class I molecules and other immunoactive molecules on tumor cells The aim of this master thesis project was to characterize the effects of IFNγ, TNFα and of the epigenetic agents 5-azacytidine (5AC) and 5-aza-2'-deoxycytidine (5AZAD) on the expression of molecules important for antigen presentation and modulation of the immune responses against tumors (MHC class I molecules and other immunoactive molecules CD54, CD80, B7-H1, B7-H2 and CD1d) on tumor cells. The experimental model used for this purpose were the HPV16-associated murine tumor cell lines, either MHC class I positive or negative. The goal was to determine the changes in surface expression of these molecules after treatment by FACS studies and also the expression at the mRNA level using qPCR. Expression of these proteins was also compared in the experiments in vitro on tumor cell lines and ex vivo on tumor cells explanted from animals. The most interesting result is the observation that 5AZAD increases the expression of B7-H1 which inhibits T cell mediated immune response and that 5AZAD and IFNγ act synergistically in the induction of the expression of MHC class I, CD54 and B7-H1 molecules. Klíčová slova: imunoeditace, protinádorová imunita, HVP16, MHC glykoproteiny I. třídy, B7-H1, IFNγ, TNFα,...Katedra genetiky a mikrobiologieDepartment of Genetics and MicrobiologyFaculty of SciencePřírodovědecká fakult