Browsing by Subject "Autoimmunity."
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Item Open Access Analysis of X chromosome inactivation in primary and secondary Sjogren syndrome(Bilkent University, 2008) Kantar, MeldaSjogren Syndrome is an autoimmune disease with one of the highest prevalences and unknown etiology. The majority of the patients (~90%) are female similar to several other autoimmune diseases. Based on this observation, a hypothesis was proposed stating that X chromosome inactivation (XCI) could be involved in female predisposition to autoimmunity. XCI is a physiological mechanism which takes place early in development resulting in the transcriptional silencing of one of the pair of X chromosomes at random in each cell. A significant deviation from a random distribution of two cell populations with paternal and maternal X chromosome inactive is called skewed XCI. Skewing in the dendritic cell population involved in tolerance induction in the thymus was proposed to cause escape of autoreactive lymphocytes and result in autoimmunity (Immunol Today, 19, 352-7, 1998). Skewed XCI was observed in scleroderma (Arth Rheum 52, 1564-70, 2005) and autoimmune thyroiditis (Eur J Hum Genet 14, 791-7, 2006). But this observation is not true for all autoimmune diseases. For example, the XCI profiles of primary biliary cirrhosis patients are similar to normal controls (Hepatol Res 37, Suppl 3, 384-8, 2007). The aim of this study is to determine the XCI profiles of patients diagnosed with primary Sjogren Syndrome, manifesting exocrinopathy or secondary Sjogren Syndrome displaying additional systemic features. DNA was isolated from the peripheric blood samples of 78 Sjogren syndrome patients and 160 controls. XCI profile was determined by the genotyping of a polymorphism in the androgen receptor (AR) gene. For this analysis, restriction enzyme HpaII was used which does not cut methylated regions. Analysis was done with Genescan Abi Prism 310 or 8% polyacrylamide gel electrophoresis and densitometric analysis. Extreme skewing (>90%) of XCI was observed in 3 (5.9%) patients and 3 controls (2.4%) samples (P = 0.3651). Our findings do not support a role for skewed XCI in Sjogren Syndrome.Item Open Access Enhanced immunomodulatory applications of nucleic acid encapsulating liposomes(Bilkent University, 2009) Erikçi, ErdemRecent studies have demonstrated that innate immune system has great ability to discriminate self from non-self through the action of innate immune receptors. The most extensively studied innate immune receptor family is the Toll-like receptors (TLRs). Endosomal/intracellular TLR3, TLR7/8 and TLR9 recognize dsRNA, ssRNA and unmethylated CpG DNA respectively. Upon activation following recognition of nucleic acids by endosomal TLRs, B cells secrete IL6, dendritic cells and macrophages secrete type I IFNs, IL12 and NK cells secrete IFNγ which yields Th1 type immune response. Modulating the immune response to mount such an immune response by TLR ligands are harnessed in medical applications such as anticancer, antiviral, antibacterial therapies, anti-allergen, as vaccine adjuvant and as immunoprotective agents. Promising clinical applications of TLR ligand nucleic acids are hampered due to their premature in vivo digestion by endonucleases and rapid clearance via serum protein absorption leading to limited stability and bioavailability. A powerful tool to overcome this problem can be achieved by encapsulating TLR ligands within liposomes, which increase in vivo stability as well as augment targeting and internalization to relevant innate immune cells. In this study we aimed to establish the most immunostimulatory liposome type encapsulating or coencapsulating CpG ODN and pIC. Five different liposomes possessing different physicochemical properties were prepared and their immunostimulatory potential when nucleic acid TLRs are loaded, were assessed. Following stimulation of splenocytes with combinations of these liposome types we have observed that neutral, anionic and stealth liposome encapsulating D-ODN, led to a dose dependent significantly higher IFNγ production over free counterpart. Stealth liposome encapsulating pIC induced both IL6 and IFNγ 10 and 250 fold respectively over free pIC. Neutral and anionic liposome coencapsulating D-ODN with pIC were very strong type 1 IFN as well as Th1 cytokine inducers both in vitro and ex vivo. Then, we immunized B6 mice with anionic liposome coencapsulating D-ODN and OVA to establish the immuno-adjuvant properties of liposome formulations in vivo. We assessed primary and secondary anti-OVA IgG subclass responses of mice. Results strongly implicated that even after primary immunization, we could obtain significantly higher anti-OVA IgG and IgG2a response over OVA mixed D-ODN group. After booster injection, 22 fold more IgG, 26 fold more IgG1 and 13 fold more IgG2a were obtained compared to free group. Our findings demonstrated that when simultaneous delivery of adjuvant (D-ODN) and antigen (OVA) within a proper depot system is given to a host, very potent antigen specific immunity is achieved. This knowledge will pave the way to design of novel effective vaccine adjuvants.Item Open Access Immunoregulatory activities of nanoparticle-forming oligodeoxynucleotides(Bilkent University, 2009) Karatepe, KutayInnate immune system is activated by a wide range of microbial by products leading to an immediate immune activation primarily designed to neutralize and control the invading insult. The cells of the innate immune system also instruct the development of antigen-specific adaptive immunity. While TLR9 is triggered by bacterial DNA, extended and over-exuberant immune response poses a threat since it may exacerbate cell and tissue destruction leading to organ failure. Telomeric TTAGGG conserved motifs are previously reported to antagonize TLR mediated events. The down-regulatory effect of these motifs may help to restore the desired homeostatic balance of the immune system. While CpG ODN patterned after bacterial DNA can be harnessed in different clinical settings to provide an advantage to host to resist infectious diseases, control tumor growth or alleviate allergic symptoms, the immunosuppressive telomeric motifs could be effectively applied in controlling systemic anti-inflammatory or autoimmune related disorders. Several challenges exist in the utilization of synthetic ODNs in the clinic. The first challenge is that conventional classes of synthetic ODNs exhibit different properties. K-type ODNs are more effective in proliferation and activation of B cells and DC. D-type ODNs are in nanoparticle forms, lead to anti-viral type I IFN production and mature monocytes into DCs. Of note, the efficacy of these synthetic ODNs is reduced under physiological conditions due to premature clearance and low levels of internalization. Moreover, D-ODNs as one of the most potent IFNα inducing TLR9 ligands possess a large-scale production problem due to 3’polyGruns, which hamper their entry into the clinic. We have designed a novel class of ODN, designated as ODN420, devoid of polyGs that can undergo nanoparticle formation necessary for its IFNα induction. Ex vivo stimulation of mouse splenocytes and in vivo administration of ODN420 have revealed that this ODN exhibits higher immunostimulatory potential and is more stable than most commonly used ODNs due to its nanoparticle-forming ability. Another interesting finding is that ODN420 with the natural phosphodiester (PO) backbone is at least as potent as its more stable counterpart with the modified phosphorothioate backbone. Furthermore, it combines superior properties of conventional classes of K and D-ODNs. These results have been reproduced in human peripheral blood mononuclear cells by various assays. Next, we have analyzed whether this ODN could be utilized as a vaccine adjuvant and an anti-cancer agent with two independent experiments. Our immunization results demonstrate that ODN420 induces a higher level of Th1-mediated response than conventional ODNs and is a promising candidate as a vaccine adjuvant. This response is hampered when ODN420 is used in combination with ODN-A151. In the tumor xenograft model, ODN420 has promoted partial remission of the tumors or delayed the tumor growth. This knowledge will pave the way for more effective immunotherapeutic approaches.Item Open Access Suppressive oligodeoxynucleotides as a TLR antagonist : efforts to treat autoimmune diseases(Bilkent University, 2007) Yağcı, Fuat CemSynthetic oligodeoxynucleotides (ODN) expressing suppressive TTAGGG motifs effectively down-regulate the production of proinflammatory and Th1 cytokines elicited by a variety of Toll-Like Receptor (TLR) dependent or independent immune stimuli. Although initially identified by their ability to block CpG-induced immune activation, this class of suppressive ODN (typified by ODN A151) was subsequently shown to block multiple forms of immune stimulation and to be effective in the prevention and treatment of pathologic autoimmune diseases. Endotoxin-induced uveitis (EIU) is an established animal model of acute ocular inflammation. It is induced by either systemic or intravitreal administration of lipopolysaccharide (LPS). FMF is an autosomal recessive periodic fever disease characterized by recurrent, self-limiting, febrile, inflammatory attacks of the serosal membranes such as peritoneum, pleura, and synovia. FMF patients in clinical remission are reported to have increased baseline inflammation. Present study aims to demonstrate that the downregulatory effect of the suppressive DNA could prove benefit to alleviate the symptoms associated with i) LPS induced EIU in rabbit or murine models as model for local autoimmune disease and ii) Familial Mediterranean Fever a model for systemic autoinflammatory disease. Results from this research strongly implicated that A151 treated EIU induced animals downregulated IL6 and IL1b cytokine secretion or expression as well as chemokines such as or MIP3a, or iNOS levels. Our data suggest that FMF patient PBMCs to that of healthy donor`s blood were more responsive to TLR ligand stimulation and A151 incubation strongly reversed this activation and suppressed certain key cytokine/chemokine levels.Item Open Access X chromosome inactivation in female predisposition to autoimmunity(Bilkent University, 2008) Uz, ElifThe high female preponderance is thought to be important in identifying the etiological factors. Sex hormones, pregnancy related microchimerism, and environmental factors are investigated as likely candidates. Disturbed Xchromosome inactivation (XCI) is another candidate, which may contribute to the break-down of self-tolerance. In this study, we tested the hypothesis that “loss of mosaicism” for X-linked gene expression may contribute to autoimmune disease etiology. Therefore, XCI status of healthy individuals and patients diagnosed with scleroderma (SSc), autoimmune thyroiditis (AITDs), Sjogren’s syndrome (SICCA), and juvenile idiopathic arthritis (JIA) in the Turkish population were analyzed by genotyping the methylation status of a CAG polymorphism in the androgen receptor (AR) gene. Extremely skewed XCI was observed in a significant proportion of SSc (OR: 38.9; P<0.0001), AITDs (OR: 9.6; P<0.0001), and JIA (OR: 4.4; P=0.0022). Further genotyping of AITDs in Tunisian and SSc in the US population supported the initial observations (OR: 3.8; P=0.0046; OR: 3.8; P<0.0001) respectively. Analysis of rheumatoid arthritis (RA) in the Tunisian population suggests that extremely skewed XCI (OR: 6.7; P<0.0001) could be involved in disease pathogenesis. Moreover, pre-eclampsia, a disease in which autoimmunity may be important, skewed XCI was observed (OR; 11.7; P=0.0005). However, in SICCA random patterns of XCI was observed suggesting that extreme skewing is not a common feature of all female prevalent autoimmune disorders. In conclusion, our results suggest that extremely skewed XCI may be important factor in autoimmune disease pathogenesis.