The Immune Response to Melanoma Is Limited by Thymic Selection of Self-Antigens

The expression of melanoma-associated antigens (MAA) being limited to normal melanocytes and melanomas, MAAs are ideal targets for immunotherapy and melanoma vaccines. As MAAs are derived from self, immune responses to these may be limited by thymic tolerance. The extent to which self-tolerance prevents efficient immune responses to MAAs remains unknown. The autoimmune regulator (AIRE) controls the expression of tissue-specific self-antigens in thymic epithelial cells (TECs). The level of antigens expressed in the TECs determines the fate of auto-reactive thymocytes. Deficiency in AIRE leads in both humans (APECED patients) and mice to enlarged autoreactive immune repertoires. Here we show increased IgG levels to melanoma cells in APECED patients correlating with autoimmune skin features. Similarly, the enlarged T cell repertoire in AIRE−/− mice enables them to mount anti-MAA and anti-melanoma responses as shown by increased anti-melanoma antibodies, and enhanced CD4+ and MAA-specific CD8+ T cell responses after melanoma challenge. We show that thymic expression of gp100 is under the control of AIRE, leading to increased gp100-specific CD8+ T cell frequencies in AIRE−/− mice. TRP-2 (tyrosinase-related protein), on the other hand, is absent from TECs and consequently TRP-2 specific CD8+ T cells were found in both AIRE−/− and AIRE+/+ mice. This study emphasizes the importance of investigating thymic expression of self-antigens prior to their inclusion in vaccination and immunotherapy strategies

The spin label amino acid TOAC and its uses in studies of peptides: chemical, physicochemical, spectroscopic, and conformational aspects

We review work on the paramagnetic amino acid 2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid, TOAC, and its applications in studies of peptides and peptide synthesis. TOAC was the first spin label probe incorporated in peptides by means of a peptide bond. In view of the rigid character of this cyclic molecule and its attachment to the peptide backbone via a peptide bond, TOAC incorporation has been very useful to analyze backbone dynamics and peptide secondary structure. Many of these studies were performed making use of EPR spectroscopy, but other physical techniques, such as X-ray crystallography, CD, fluorescence, NMR, and FT-IR, have been employed. The use of double-labeled synthetic peptides has allowed the investigation of their secondary structure. A large number of studies have focused on the interaction of peptides, both synthetic and biologically active, with membranes. In the latter case, work has been reported on ligands and fragments of GPCR, host defense peptides, phospholamban, and β-amyloid. EPR studies of macroscopically aligned samples have provided information on the orientation of peptides in membranes. More recent studies have focused on peptide–protein and peptide–nucleic acid interactions. Moreover, TOAC has been shown to be a valuable probe for paramagnetic relaxation enhancement NMR studies of the interaction of labeled peptides with proteins. The growth of the number of TOAC-related publications suggests that this unnatural amino acid will find increasing applications in the future

Transcriptomic analysis supports similar functional roles for the two thymuses of the tammar wallaby

Background: The thymus plays a critical role in the development and maturation of T-cells. Humans have a single thoracic thymus and presence of a second thymus is considered an anomaly. However, many vertebrates have multiple thymuses. The tammar wallaby has two thymuses: a thoracic thymus (typically found in all mammals) and a dominant cervical thymus. Researchers have known about the presence of the two wallaby thymuses since the 1800s, but no genome-wide research has been carried out into possible functional differences between the two thymic tissues. Here, we used pyrosequencing to compare the transcriptomes of a cervical and thoracic thymus from a single 178 day old tammar wallaby.Results: We show that both the tammar thoracic and the cervical thymuses displayed gene expression profiles consistent with roles in T-cell development. Both thymuses expressed genes that mediate distinct phases of T-cells differentiation, including the initial commitment of blood stem cells to the T-lineage, the generation of T-cell receptor diversity and development of thymic epithelial cells. Crucial immune genes, such as chemokines were also present. Comparable patterns of expression of non-coding RNAs were seen. 67 genes differentially expressed between the two thymuses were detected, and the possible significance of these results are discussed.Conclusion: This is the first study comparing the transcriptomes of two thymuses from a single individual. Our finding supports that both thymuses are functionally equivalent and drive T-cell development. These results are an important first step in the understanding of the genetic processes that govern marsupial immunity, and also allow us to begin to trace the evolution of the mammalian immune system

Autonomous role of medullary thymic epithelial cells in central CD4+ T cell tolerance

International audienceMedullary thymic epithelial cells (mTECs) serve an essential function in central tolerance through expressing peripheral tissue-antigens. These antigens may be transferred to and presented by dendritic cells. Therefore, it is unclear whether mTECs, besides being an 'antigen-reservoir', also serve a mandatory function as antigen presenting cells. Here, we reduced MHC class II on mTECs through transgenic expression of a C2TA-specific 'designer miRNA'. This resulted in an enlarged polyclonal CD4 single-positive compartment and, among thymocytes specific for model-antigens expressed in mTECs, enhanced selection of regulatory T cells (Treg) at the expense of deletion. Our data document an autonomous contribution of mTECs to dominant and recessive mechanisms of CD4+ T cell tolerance and support an avidity model of Treg development versus deletion

Small-molecule inhibitors and probes for ubiquitin- and ubiquitin-like-specific proteases.

There's always a catch. The post-translational modification of proteins with ubiquitin (Ub) or ubiquitin-like (Ubl) modifiers is an important signal in the regulation of a variety of biological processes, such as degradation and regulation of gene expression. Here we report the synthesis of a panel of peptide vinyl sulfones (see scheme) harboring various portions of the Ub C terminus by using a safety-catch linker. Depending on their length, such compounds can efficiently target Ubl-specific proteases. © 2005 Wiley-VCH Verlag GmbH and Co. KGaA

Metallophilic macrophages are fully developed in the thymus of autoimmune regulator (Aire)-deficient mice

Copyright © Springer-Verlag 2009 Thymic metallophilic macrophages represent a significant component in the thymus physiology. Recently, we showed their presence to be dependent on functional lymphotoxin-β receptor (LTβR) signaling pathway. However, it is unknown whether the development of metallophilic macrophages also requires the Autoimmune regulator (Aire) transcription factor, as suggested by some studies for medullary thymic epithelial cells, or perhaps the presence of Aire-expressing thymic epithelial cells themselves. Therefore, we investigated the presence of metallophilic macrophages in Aire-deficient thymus. Our study shows that the metallophilic macrophages are fully developed in the Aire-deficient thymus; their development is not regulated via Aire transcription factor and does not require the presence of Aire-expressing epithelial cells. On the contrary, in alymphoplasia (ALY) mice (deficient in nuclear factor-kappaB-inducing kinase, NIK), which we used as negative control, thymic metallophilic macrophages are completely lacking, similarly as in LTβR-deficient animals. Together, these results show that the development/maintenance of thymic metallophilic macrophages is executed via LTβR circumventing the Aire transcription factor. Thus, we shed a new light on the molecular requirements for development of these cells and also show that LTβR pathway is a common developmental regulator of metallophilic macrophages in different lymphatic organs (i.e., thymus and spleen).Thymic metallophilic macrophages represent a significant component in the thymus physiology. Recently, we showed their presence to be dependent on functional lymphotoxin-beta receptor (LT beta R) signaling pathway. However, it is unknown whether the development of metallophilic macrophages also requires the Autoimmune regulator (Aire) transcription factor, as suggested by some studies for medullary thymic epithelial cells, or perhaps the presence of Aire-expressing thymic epithelial cells themselves. Therefore, we investigated the presence of metallophilic macrophages in Aire-deficient thymus. Our study shows that the metallophilic macrophages are fully developed in the Aire-deficient thymus; their development is not regulated via Aire transcription factor and does not require the presence of Aire-expressing epithelial cells. On the contrary, in alymphoplasia (ALY) mice (deficient in nuclear factor-kappaB-inducing kinase, NIK), which we used as negative control, thymic metallophilic macrophages are completely lacking, similarly as in LT beta R-deficient animals. Together, these results show that the development/maintenance of thymic metallophilic macrophages is executed via LT beta R circumventing the Aire transcription factor. Thus, we shed a new light on the molecular requirements for development of these cells and also show that LT beta R pathway is a common developmental regulator of metallophilic macrophages in different lymphatic organs (i.e., thymus and spleen).Novica M. Milićević, Živana Milićević, Miloš D. Miljković, Milica Labudović-Borović, Martti Laan, Pärt Peterson, Kai Kisand, Hamish S. Scott, Ning Qu and Jürgen Westerman

Wormwood Review Project

Medullary thymic epithelial cells (mTECs) are critical in establishing and maintaining the appropriate microenvironment for negative selection and maturation of immunocompetent T cells with a self-tolerant T cell antigen receptor repertoire. Cues that direct proliferation and maturation of mTECs are provided by members of the tumor necrosis factor (TNF) superfamily expressed on developing thymocytes. Here we demonstrate a negative role of the morphogen TGF-beta in tempering these signals under physiological conditions, limiting both growth and function of the thymic medulla. Eliminating TGF-beta signaling specifically in TECs or by pharmacological means increased the size of the mTEC compartment, enhanced negative selection and functional maturation of medullary thymocytes as well as the production of regulatory T cells, thus reducing the autoreactive potential of peripheral T cells