Tolérance (immunologie) | EPFL Graph Search

vignette|À l'intérieur du thymus, les lymphocytes T sont soumis à un examen minutieux ; ils subissent une sélection positive et négative En immunologie, la tolérance est l'absence ou le faible niveau de réaction inflammatoire face à un antigène. Son contraire est l'anaphylaxie. On distingue : *la tolérance centrale, relative à la maturation des lymphocytes B et T, ainsi qu'à la reconnaissance et tolérance du soi ; *la tolérance périphérique, relative aux lymphocytes B et T matures dans le système lymphatique périphérique ainsi qu'à leur faible activation en cas d'absence de promoteur de la réaction inflammatoire, ou en présence de facteurs de régulation (diminution) de la réaction inflammatoire. Le processus induisant une tolérance à un antigène donné s'appelle la tolérogenèse. Elle n'est possible que dans un organisme immunocompétent sous certaines conditions. On identifie entre autres certaines cellules immunitaires relativement en amont du processus : les tTreg, les pTreg, les iTr

Mechanisms of tolerance induction by erythrocyte-targeted antigens

Alizée Jéléna Grimm

Immune-mediated disorders such as autoimmune diseases, graft-versus-host disease or allergies, are a major contemporary burden. Despite significant advances in the field of immunological tolerance, immunosuppressive drugs are still the current hallmark for treatment of transplanted recipients or patients with autoimmune disorders. While these drugs ameliorate the lives of the patients, benefits are unfortunately counterbalanced by the need for life-long treatment and non-negligible adverse side effects. The development of a therapy affecting the immune system in an antigen-specific manner is thus required for these and many other situations. Pursuing this aim, our laboratory has recently developed a novel approach to induce antigen-specific T cell tolerance through targeting antigens to erythrocytes in situ. Apoptotic cells are known to be processed tolerogenically in vivo. The concept of our therapeutic approach is based on the premise that as aged erythrocytes are cleared through an apoptotic-like mechanism, the surface-bound antigen payload will be cleared tolerogenically along with the eryptotic debris. While great strides have been made in showing the potential of the approach in inducing antigen-specific immune tolerance, little is known about the mechanisms driving tolerance. The aim of this thesis is to further understand the mechanisms behind induction of tolerance by erythrocyte-targeted antigens. Aspects such as memory of tolerance, dependence on T cell receptor (TCR) affinity for the peptide major histocompatibility complex (pMHC) and molecular pathways involved in this process will be addressed. Using ovalbumin (OVA) as a model protein antigen, we demonstrated long-term induction of immune tolerance after treatment with erythrocyte-targeted antigens, and requirement of CD25+FOXP3+ regulatory T cells for maintenance of the tolerogenic state. Signaling through programmed death-1/programmed death ligand-1 (PD-1/PD-L1), but not through cytotoxic T lymphocyte antigen 4 (CTLA4), was shown to be required for antigen-specific T cell deletion, anergy and expression of regulatory markers. The recent evidences of a direct implication of low affinity T cells as active contributor of self-destruction in autoimmunity raise questions regarding the ability of peripheral tolerance to deal with T cells of lower affinities. To explore the impact of TCR-pMHC affinity on induction of peripheral tolerance by erythrocyte-targeted antigens, erythrocyte-targeted altered peptide ligands with gradated affinity for the TCR of OTI CD8+ T cells were used. We demonstrated that tolerance induction is dependent on TCR strength as well as activation state of low affinity T cells. Finally, RNA sequencing was performed to determine how genes are regulated in CD8+ T cells and which pathways are activated after treatment with erythrocyte-targeted antigens. Comparison with gene sets characteristic of T cells undergoing anergy or deletional tolerance revealed the similarity between response induced by the natural event of peripheral tolerance and tolerance induced by erythrocyte-targeted antigens. Together, these results pave the way for the continued exploration of erythrocyte-targeting for prophylactic and therapeutic modulation of the immune system.

EPFL2016

Introducing tolerance to foreign and partly foreign proteins by erythrocyte binding and artificial glycosylations

Kym Lorenz Brünggel

Over the last few years, protein drugs have steadily gained importance in the clinic. Compared to small molecule drugs, protein drugs are taken up by antigen presenting cells, which degrade the proteins into peptides that are then presented on major histocompatability complex I and II to CD8+ respectively CD4+ T-cells. CD4+ T-cells are then able to activate B-cells, which upon activation will produce anti-drug antibodies. While anti-drug antibodies have mostly been viewed as a safety risk leading to drug injection related side effects, they have recently been proven to diminish the efficacy of the treatment. High antibody titers against Humira, a clinically approved monoclonal antibody used to treat rheumatoid arthritis, have been associated with low serum drug concentration and high disease activity score, ultimately leading to treatment failure. Two approaches to induce tolerance were developed in the Hubbell lab. One approach utilizes protein variants that are designed to bind to circulating erythrocytes. As 1 % of erythrocytes undergo apoptosis each day and are taken up by antigen presenting cells, along with the bound protein, they are presented to the immune system in a non-inflammatory tolerogenic fashion. Immunological tolerance is thereby induced against the apoptotic erythrocyte debris and the associated bound protein. The second approach uses synthetic glucose, galactose or mannose polymers conjugated to the target protein. The polymers target C-type lectins, which are known to clear apoptotic debris, leading to presentation of the protein by hepatic antigen presenting cells in a tolerogenic liver microenvironment. This thesis investigates the potential of these approaches to induce tolerance towards protein drugs. Arylsulfatase B was used as a model protein to investigate the potential of tolerance induction by targeting circulating erythrocytes, as 97% of patients receiving arylsulfatase B develop anti-drug antibodies. An erythrocyte binding variant of arylsufatase B was created by chemically conjugating the erythrocyte binding peptide ERY1 to arylsulfatse B. In mice receiving two doses of ERY1-arylsulfatase B one week apart followed by weekly doses of arylsulfatase B a significant delay of four week in the production of anti-drug Antibodies was found when compared to mice receiving weekly doses of only arylsulfatase B. To investigate the ability of synthetic glyco-polymers to induce tolerance towards protein drugs we used asparaginase as model protein. Between 37.5 % to 75% of patients treated with asparaginase develop anti-drug antibodies. Administering three intravenous injections of asparaginase-conjugated to glucose polymers before eight weeks of treatment with asparaginase significantly reduced anti-drug antibody titers by a factor of 125 when compared to animals only receiving eight weeks of treatment with asparaginase. Three pre-injections with asparaginase conjugated to the galactose or mannose polymer led to a reduction in anti-drug antibody titers by a factor of 12 respectively 400 after 5 weeks of treatment with asparaginase when compared to mice receiving only asparaginase for 5 weeks. These results indicates that synthetic glyco polymers, especially mannose and glucose based ones, are able to induce long term tolerance towards asparaginase. Synthetic glucose and mannose polymers therefore represent an excellent molecular approach to induce tolerance towards protein drugs.

EPFL2018

Elucidating the role of lymphatic vessels within the tumor microenvironment of breast cancer

Ingrid Maria van Mier

Breast cancer is the most common cancer in women worldwide, with an estimated 1.7 million newly diagnosed cases in 2012. Despite the many clinical manifestations, metastatic disease is the main cause of death, and is responsible for 90% of all breast cancer-related deaths. Aggressive carcinomas of the breast preferentially spread via the lymphogenous route, and often co-opt and actively remodel the lymphatic vasculature in order to invade and metastasize to their draining lymph nodes (LNs) and, ultimately, to distant organs. Indeed, expression of vascular endothelial growth factor (VEGF)-C, the principal lymphangiogenic growth factor, by the tumor or recruited ancillary cells has been shown to correlate both with LN and distant metastasis, and shorter overall survival (OS), and LN status represents an important prognostic factor for patients diagnosed with breast cancer. Although traditionally considered as passive conduits that solely mediate tumor cell escape, more recent research aimed at discerning the interactions between the developing tumor and its associated lymphatic vessels has revealed that the lymphatic vasculature actively promotes lymphogenous metastasis of invasive tumor cells. Likewise, collaborative interactions between tumor cells and a multitude of other tissue-resident and recruited ancillary cells, which together constitute the tumor microenvironment, not only coercively contribute to tumor growth, progression and metastasis, but also suggest that interactions among primed stromal cells themselves may be important in the process of metastatic dissemination as well. Notably, expansion of tumor-associated lymphatic vessels in the tumor periphery leads to increased lymphatic drainage from the tumor to the tumor-draining LN, and interstitial flow-induced mechanical changes may alter tensional homeostasis within the tumor through stimulation of local fibroblasts that remodel and stiffen the extracellular matrix (ECM). Furthermore, VEGF-C-induced remodeling of the tumor-associated lymphatic vasculature has been shown to directly suppress the anti-tumor immune response, thereby promoting tolerance to the nascent tumor. Thus, to explore whether tumor-associated lymphatic vessels promote tumor metastasis not only via interactions with the incipient tumor, but also through cross-talk with the surrounding stromal cells, the different components of the tumor microenvironment, specifically tensional homeostasis and anti-tumor immunity, were evaluated upon modulation of lymphatic vessel growth in various experimental models of breast cancer. Accordingly, inhibition of VEGFR-3-mediated signaling upon administration of an antagonistic antibody in a genetically engineered preclinical mouse model specifically reduced the number of lymphatic endothelial cells (LECs) in the tumor, whereas conversely, orthotopic inoculation of a stable murine breast cancer cell line with enhanced expression of VEGF-C induced an expansion of the lymphatic endothelium. Although either experimental approach affected either regional or distant metastatic dissemination of the primary tumor to LN or the lungs, respectively, these effects did not seem to be mediated by interactions of the tumor-associated lymphatic vasculature with the tumor microenvironment in these particular experimental models.

EPFL2017