Autophagy controls IL-1beta secretion by targeting pro-IL-1beta for degradation.

Autophagy is a key regulator of cellular homeostasis that can be activated by pathogen-associated molecules and recently has been shown to influence IL-1β secretion by macrophages. However, the mechanisms behind this are unclear. Here, we describe a novel role for autophagy in regulating the production of IL-1β in antigen-presenting cells. After treatment of macrophages with Toll-like receptor ligands, pro-IL-1β was specifically sequestered into autophagosomes, whereas further activation of autophagy with rapamycin induced the degradation of pro-IL-1β and blocked secretion of the mature cytokine. Inhibition of autophagy promoted the processing and secretion of IL-1β by antigen-presenting cells in an NLRP3- and TRIF-dependent manner. This effect was reduced by inhibition of reactive oxygen species but was independent of NOX2. Induction of autophagy in mice in vivo with rapamycin reduced serum levels of IL-1β in response to challenge with LPS. These data demonstrate that autophagy controls the production of IL-1β through at least two separate mechanisms: by targeting pro-IL-1β for lysosomal degradation and by regulating activation of the NLRP3 inflammasome.

Retrovirus-host interactions. The mouse mammary tumor virus model.

Mouse mammary tumor virus (MMTV) is a retrovirus which can induce mammary carcinomas in mice late in life by activation of proto-oncogenes after integration in their vicinity. Surprisingly, it requires a functional immune system to achieve efficient infection of the mammary gland. This requirement became clear when it was discovered that it has developed strategies to exploit the immune response. Instead of escaping immune detection, it induces a vigorous polyclonal T-B interaction which is required to induce a chronic infection. This is achieved by activating and then infecting antigen presenting cells (B cells), expressing a superantigen on their cell surface and triggering unlimited help by the large number of superantigen-specific T cells. The end result of this strong T-B interaction is the proliferation and differentiation of the infected B cells leading to their long term survival.

Immune Microenvironment in Colorectal Cancer: A New Hallmark to Change Old Paradigms

Impact of immune microenvironment in prognosis of solid tumors has been extensively studied in the last few years. Specifically in colorectal carcinoma, increased knowledge of the immune events around these tumors and their relation with clinical outcomes have led to consider immune microenvironment as one of the most important prognostic factors in this disease. In this review we will summarize and update the current knowledge with respect to this intriguing and complex new hallmark of cancer, paying special attention to infiltration by T-infiltrating lymphocytes and their subtypes in colorectal cancer, as well as its eventual clinical translation in terms of long-term prognosis. Finally, we suggest some possible investigational approaches based on combinatorial strategies to trigger and boost immune reaction against tumor cells.

Secretory immunoglobulin A: well beyond immune exclusion at mucosal surfaces.

At mucosal surfaces, secretory IgA (SIgA) antibodies serve as the first line of defense against microorganisms through a mechanism called immune exclusion that prevents interaction of neutralized antigens with the epithelium. In addition, SIgA plays a role in the immune balance of the epithelial barrier through selective adhesion to M cells in intestinal Peyer's patches. This mediates the transepithelial retro-transport of the antibody and associated antigens from the intestinal lumen to underlying gut-associated organized lymphoid tissue. In Peyer's patches, SIgA-based immune complexes are internalized by underlying antigen-presenting cells, leaving the antigen with masked epitopes, a form that limits the risk of overwhelming the local immune protection system with danger signals. This translates into the onset of mucosal and systemic responses associated with production of anti-inflammatory cytokines and limited activation of antigen-presenting cells. In the gastrointestinal tract, SIgA exhibits thus properties of a neutralizing agent (immune exclusion) and of an immunopotentiator inducing effector immune responses in a noninflammatory context favorable to preserve local homeostasis.

New insights into dendritic cell biology and histiocytosis through a transgenic tumor model

SUMMARY The effective development of an immune response depends on the careful interplay and the regulation between innate and adaptive immunity. As the dendritic cells (DCs) are equipped with many receptors, such as Toll-like receptors, which can detect the presence of infection by recognizing different component of bacteria, fungi and even viruses, they are the among the first cells to respond to the infection. Upon pathogen challenge, the DCs interpret the innate system activation as a maturation signal, resulting in the migration of the DCS to a draining lymph node site. There, activated DCs present efficiently antigens to naïve T cells, which are in turn activated and initiate adaptive immunity. Therefore, DCs are the main connectors between innate and adaptive immune systems. In addition to be the most efficient antigen- presenting cells, DCs play a central role in the regulation of immune responses and immune tolerance. Despite extensive research, many aspects related to DC biology are still unsolved and/or controversial. The low frequency of DCs in vivo often hamper study of DC biology and in vitro-derived DCs are not suited to address certain questions, such as the development of DC. We sought of transforming in vivo the DCs through the specific expression of an oncogene, in order to obtain unlimited numbers of these cells. To achieve this goal, transgenic mouse lines expressing the SV40 Large T oncogene under the control of the CD1 1 c promoter were generated. These transgenic mice are healthy until the age of three to four months without alterations in the DC biology. Thereafter transgenic mice develop a fatal disease that shows features of a human pathology, named histiocytosis, involving DCs. We demonstrate that the disease development in the transgenic mice correlates with a massive accumulation of transformed DCs in the affected organs. Importantly, transformed DCs are immature and fully conserve their capacity to mature in antigen presenting cells. We observe hyperproliferation of transformed DCs only in the sick transgenic mice. Surprisingly, transformed DCs do not proliferate in vitro, but transfer of the transformed DCs into immunodeficient or tolerant host leads to tumor formation. Altoghether, the transgenic mouse lines we have generated represent a valuable tumor model for human histiocytosis, and provide excellent tools to study DC biology. RESUME Le développement d'une réponse immunitaire efficace dépend d'une minutieuse interaction et régulation entre l'immunité innée et adaptative. Comme les cellules dendritiques (DCs) sont équipées de nombreux récepteurs, tels que les récepteurs Toll-like, qui peuvent détecter la présence d'une infection en reconnaissant différents composants bactériens, issus de champignons ou même viraux, elles sont parmi les premières cellules à répondre à l'infection. Suite à la stimulation induite par le pathogène, les DCs interprètent l'activation du système immunitaire inné comme un signal de maturation, résultant dans la migration des DCs vers le ganglion drainant le site d'infection. Là, les DCs actives présentent efficacement des antigènes aux cellules T, qui sont à leur tour activées et initient les systèmes d'immunité adaptative. Ainsi, les DCs forment le lien principal entre les réponses immunitaires innées et adaptatives. En plus d'être les cellules présentatrices d'antigènes les plus efficaces, les DCs jouent un rôle central dans la régulation du système immunitaire et dans le phénomène de tolérance. Malgré des recherches intensives, de nombreux aspects liés à la biologie des DCs sont encore irrésolus et/ou controversés. La faible fréquence des DCs in vivo gêne souvent l'étude de la biologie de ces cellules et les DCs dérivées in vitro ne sont pas adéquates pour adresser certaines questions, telles que le développement des DCs. Afin d'obtenir des quantités illimitées de DCs, nous avons songé à transformer in vivo les DC grâce à l'expression spécifique d'un oncogène. Afin d'atteindre ce but, nous avons généré des lignées de souris transgéniques qui expriment l'oncogène SV40 Large T sous le contrôle du promoter CD1 le. Ces souris transgéniques sont saines jusqu'à l'âge de trois à quatre mois et ne présentent pas d'altération dans la biologie des DCs. Ensuite, les souris transgéniques développent une maladie présentant les traits caractéristiques d'une pathologie humaine nommée histiocytose, qui implique les DCs. Nous montrons que le développement de cette maladie corrèle avec une accumulation massive des DCs transformées dans les organes touchés. De plus, les DCs transformées sont immatures et conservent leur capacité à différencier en cellules présentatrices d'antigène. Nous observons une hyper-prolifération des DCs transformées seulement dans les souris transgéniques malades. Etonnament, les DC transformées ne prolifèrent pas in vitro, par contre, le transfert des DCs transformées dans des hôtes immuno-déficients ou tolérant conduit à la formation de tumeurs. Globalement, les lignées de souris transgéniques que nous avons générées représentent un modèle valide pour l'histiocytose humaine, et de plus, offrent d'excellents outils pour étudier la biologie des DCs.

Differential expression of the costimulatory molecules CD86, CD28, CD152 and PD-1 correlates with the host-parasite outcome in leprosy

Leprosy is a spectral disease exhibiting two polar sides, namely, lepromatous leprosy (LL) characterised by impaired T-cell responses and tuberculoid leprosy in which T-cell responses are strong. Proper T-cell activation requires signalling through costimulatory molecules expressed by antigen presenting cells and their ligands on T-cells. We studied the influence of costimulatory molecules on the immune responses of subjects along the leprosy spectrum. The expression of the costimulatory molecules was evaluated in in vitro-stimulated peripheral blood mononuclear cells of lepromatous and tuberculoid patients and healthy exposed individuals (contacts). We show that LL patients have defective monocyte CD86 expression, which likely contributes to the impairment of the antigen presentation process and to patients anergy. Accordingly, CD86 but not CD80 blockade inhibited the lymphoproliferative response to Mycobacterium leprae. Consistent with the LL anergy, there was reduced expression of the positive signalling costimulatory molecules CD28 and CD86 on the T-cells in these patients. In contrast, tuberculoid leprosy patients displayed increased expression of the negative signalling molecules CD152 and programmed death-1 (PD-1), which represents a probable means of modulating an exacerbated immune response and avoiding immunopathology. Notably, the contacts exhibited proper CD86 and CD28 expression but not exacerbated CD152 or PD-1 expression, suggesting that they tend to develop a balanced immunity without requiring immunosuppressive costimulatory signalling.

The role of nonhematopoietic MHC class II expression in immune responses and tolerance

Si les rôles fonctionnels de diverses cellules immunitaires infiltrant des tissus enflammés sont assez bien compris, par contre, étonnamment, on connaît bien moins la capacité des cellules non hématopoïétiques résidant dans des tissus, à moduler l'activité biologique des cellules immunitaires immigrantes, et donc le résultat de la réponse immunitaire. La présentation des antigènes, dans le contexte des molécules du CMH de classe II (CMHII) à la surface des cellules présentatrices d'antigènes (CPA) professionnelles à une sous- population de lymphocytes T, est cruciale pour le développement des réponses immunitaires protectives spécifiques de l'antigène. En général, l'expression de CMHII est réservée aux CPAs. Toutefois, au cours des pathologies inflammatoires spécifiques d'organe, telles que l'auto-immunité ou la maladie inflammatoire de l'intestin, l'expression de CMHII est également induite par la cytokine interféron (IFN)-y sur des cellules non hématopoïétiques qui résident dans des tissus enflammés. Les conséquences de ce phénomène sont encore peu comprises. Dans cette étude, nous avons utilisé une souche de souris génétiquement modifiées, qui n'a pas la capacité d'induire l'expression de CMHII sur les cellules non hématopoïétiques, mais a maintenu la régulation normale d'expression de CMHII sur les cellules hématopoïétiques. Nous avons appliqué ces souris à différents modèles d'inflammation intestinale et à un modèle de maladie qui imite la maladie auto-immune de l'inflammation du muscle cardiaque (myocardite) chez l'homme. Nous avons pu montrer que, au cours de l'inflammation intestinale, l'expression du CMHII nonhématopoïétique, ou encore l'expression du CMHII par les cellules épithéliales de l'intestin, confère une protection contre la maladie, en réduisant les cellules immunitaires inflammatoires et en augmentant les cellules Τ régulatrices anti-inflammatoires. Ces résultats pourraient expliquer l'échec des traitements d'anti-IFN-γ dans les maladies intestinales inflammatoires chez l'homme. En revanche, dans la myocardite auto-immune, nos résultats indiquent que la présentation d'antigènes par les cellules non hématopoïétiques du coeur est nécessaire pour l'apparition de la pathologie cardiaque, comme nos souris sont résistantes à la maladie. Toutefois, cela n'est pas dû à un défaut d'activation des lymphocytes T, car les lymphocytes Τ des souris mutantes sont parfaitement capables de promouvoir la maladie après le transfert adoptif dans des animaux de type naturel. Nos résultats suggèrent que, durant les maladies inflammatoires spécifiques d'organe, la présentation d'antigène par des cellules non hématopoïétiques module et contribue au résultat de la réponse immunitaire d'une manière opposée, conférant soit la protection contre la maladie ou sa promotion. Nos résultats pourraient ouvrir la voie à des thérapies qui prennent en compte la contribution de la présentation d'antigènes par les cellules non hématopoïétiques, au cours des maladies inflammatoires spécifiques d'organe. - Les molécules du CMH de classe II (CMHII) sont fondamentales pour la présentation des antigènes aux lymphocytes Τ CD4+, car elles permettent le développement des réponses immunitaires spécifiques de l'antigène. Il est largement admis que l'expression de CMHII est réservée aux cellules présentatrices d'antigènes (CPA). Cependant, dans des conditions inflammatoires, l'expression de CMHII est en principe également induite par l'interféron (IFN)-y sur les cellules non hématopoïétiques, telles que les cellules épithéliales et les cardiomyocytes. Une controverse existe jusqu'à présent au sujet de la fonction de cette présentation d'antigènes non professionnelle, pour savoir si elle favorise la tolérance ou l'immunité dépendante des lymphocytes Τ in vivo. Pour répondre à cette question, nous avons testé des souris qui ne sont pas capables d'induire l'expression du CMHII sur les cellules non hématopoïétiques (souris PIV-/- K14 CIITA Tg) parmi différents modèles murins de pathologies inflammatoires, à savoir les modèles de vaccination pour induire des réponses spécifiques d'antigènes des lymphocytes B, plusieurs modèles de colite et un modèle de myocardite auto-immune expérimental (EAM). Pour cela, nous avons administré à ces souris un modèle de colite atténuée, induite par une infection chronique à Helicobacter hepaticus et par l'administration d'anticorps monoclonaux bloquant le récepteur de l'interleukine (IL)-10 (anti-IL-10R). Dans ce système, nous avons pu observer que l'expression abrogée de CMHII a aggravé la colite bactérienne, soit par les cellules non hématopoïétiques, soit exclusivement par les cellules épithéliales intestinales (CEI) dans un autre modèle murin (souris plV_fl/fl vil-Cre Tg). Ce phénotype du côlon a été associé à une augmentation des fréquences de cellules immunitaires innées, de lymphocytes Th1 CD4+, et d'expression des cytokines et de chimiokines pro-inflammatoires, y compris l'IFN-γ. Notamment, l'expression défectueuse de CMHII non hématopoïétique a également réduit les cellules Τ régulatrices (Treg) Forkhead box P3 (FoxP3)+, sans influencer les fréquences des cellules innées lymphoïdes et des cellules Th17. Ces résultats suggèrent un rôle tolérogène de CEIs CMHII+ qui contribue à l'homéostasie immunitaire intestinale. En revanche, dans le modèle d'EAM, les souris ayant subi une ablation de CMHII non hématopoïétique étaient résistantes à l'induction de la maladie, alors que la progression de la pathologie cardiaque, dans les souris de type naturel ou hétérozygotes, a été accompagnée par une régulation positive de l'expression de CMHII du myocarde. Cependant, l'inflammation cardiaque pourrait être transférée de manière adoptive depuis des souris amorcées PIV-/- K14 CIITA Tg vers des souris de type naturel, indiquant l'absence de défaut intrinsèque d'amorçage des cellules T CD4+ dans notre modèle de souris. Ces observations impliquent un rôle à jouer pour des cellules CMHII+ non hématopoïétiques résidentes du coeur, dans la promotion active de ΙΈΑΜ. En conclusion, nos résultats, provenant de diverses pathologies inflammatoires spécifiques d'organes, suggèrent un rôle complexe et divergent, soit tolérogène, soit immunogène/ pathologique, pour l'expression de CMHII non hématopoïétique au cours des pathologies inflammatoires. L'expression non professionnelle de CMHII semble influencer le résultat des réponses immunitaires en fonction de différents facteurs, tels que le tissu cible, le(s) type(s) de cellule(s) non hématopoïétique(s) participante(s) et l'origine de l'inflammation. Nos résultats pourraient potentiellement ouvrir la voie à des applications thérapeutiques, qui tiennent compte de la contribution de la présentation d'antigènes par des CPAs non professionnelles, au cours de l'inflammation spécifique d'organe. - MHC class II (MHCII) molecules are fundamental for the presentation of antigens to CD4+ Τ cells, allowing the development of antigen-specific immune responses. It is widely accepted that MHCII expression is restricted to antigen-presenting cells (APC). However, under inflammatory conditions, MHCII expression is typically also induced by interferon (IFN)-y on nonhematopoietic cells such as epithelial cells and cardiomyocytes. So far, it remains controversial whether this nonprofessional antigen-presentation function promotes CD4+ Τ cell-dependent tolerance or immunity in vivo. To address this issue, we utilised mice which lack inducible MHCII expression on nonhematopoietic cells (pIV-/- K14 CIITA Tg mice) in different mouse models of inflammatory pathologies, namely immunisation models to induce antigen-specific Β cell responses, various colitis models and a model of experimental autoimmune myocarditis (EAM). In an attenuated model of colitis induced by chronic Helicobacter hepaticus infection and treatment with anti-interleukin (IL)-10 receptor (anti-IL-10R) monoclonal blocking antibody, we observed that abrogated MHCII expression by nonhematopoietic cells or, in an alternative tamoxifen-inducible mouse model (plV_fl/fl vil-Cre Tg mice), exclusively by intestinal epithelial cells (IEC), exacerbated bacterial-driven colitis, which was associated with increased colonic frequencies of innate immune cells, CD4+ Th1 cells and expression of proinflammatory cytokines and chemokines, including IFN-γ. Notably, defective nonhematopoietic MHCII expression also resulted in reduced Forkhead box P3 (FoxP3)+ regulatory Τ (Treg) cells without influencing innate lymphoid cell (ILC) and Th17 cell frequencies. These findings suggest a tolerogenic role of MHClT lECs to contribute to intestinal immune homeostasis. In contrast, in the EAM model, mice ablated of nonhematopoietic MHCII were resistant to disease induction, whereas progression of cardiac pathology in WT and heterozygous control mice was accompanied by upregulation of myocardial MHCII expression. However, cardiac inflammation could be adoptively transferred from primed pIV-/- K14 CIITA Tg mice into WT mice, indicating no intrinsic defect of CD4+ Τ activation in our mouse model. These observations imply a role for MHCIT heart-resident nonhematopoietic cells in actively promoting EAM. In conclusion, our findings from different organ-specific inflammatory pathologies suggest a complex and diverging role - either tolerogenic or immunogenic/ pathologic - for nonhematopoietic MHCII expression during inflammatory pathologies: Nonprofessional MHCII expression appears to influence the outcome of immune responses depending on 7 factors such as the target tissue, participating non hematopoietic cell type(s) and the origin of inflammation. Our findings may potentially open the way to therapeutic applications taking into account the contribution of antigen presentation by nonprofessional, tissue-resident APCs during organ-specific inflammation.

Classification and clinical behavior of blastic plasmacytoid dendritic cell neoplasms according to their maturation-associated immunophenotypic profile.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare subtype of leukemia/lymphoma, whose diagnosis can be difficult to achieve due to its clinical and biological heterogeneity, as well as its overlapping features with other hematologic malignancies. In this study we investigated whether the association between the maturational stage of tumor cells and the clinico-biological and prognostic features of the disease, based on the analysis of 46 BPDCN cases classified into three maturation-associated subgroups on immunophenotypic grounds. Our results show that blasts from cases with an immature plasmacytoid dendritic cell (pDC) phenotype exhibit an uncommon CD56- phenotype, coexisting with CD34+ non-pDC tumor cells, typically in the absence of extramedullary (e.g. skin) disease at presentation. Conversely, patients with a more mature blast cell phenotype more frequently displayed skin/extramedullary involvement and spread into secondary lymphoid tissues. Despite the dismal outcome, acute lymphoblastic leukemia-type therapy (with central nervous system prophylaxis) and/or allogeneic stem cell transplantation appeared to be the only effective therapies. Overall, our findings indicate that the maturational profile of pDC blasts in BPDCN is highly heterogeneous and translates into a wide clinical spectrum -from acute leukemia to mature lymphoma-like behavior-, which may also lead to variable diagnosis and treatment.

Role of immune escape mechanisms in Hodgkin's lymphoma development and progression: a whole new world with therapeutic implications.

Hodgkin's lymphoma represents one of the most frequent lymphoproliferative syndromes, especially in young population. Although HL is considered one of the most curable tumors, a sizeable fraction of patients recur after successful upfront treatment or, less commonly, are primarily resistant. This work tries to summarize the data on clinical, histological, pathological, and biological factors in HL, with special emphasis on the improvement of prognosis and their impact on therapeutical strategies. The recent advances in our understanding of HL biology and immunology show that infiltrated immune cells and cytokines in the tumoral microenvironment may play different functions that seem tightly related with clinical outcomes. Strategies aimed at interfering with the crosstalk between tumoral Reed-Sternberg cells and their cellular partners have been taken into account in the development of new immunotherapies that target different cell components of HL microenvironment. This new knowledge will probably translate into a change in the antineoplastic treatments in HL in the next future and hopefully will increase the curability rates of this disease.

Enhancing efficacy of anticancer vaccines by targeted delivery to tumor-draining lymph nodes.

The sentinel or tumor-draining lymph node (tdLN) serves as a metastatic niche for many solid tumors and is altered via tumor-derived factors that support tumor progression and metastasis. tdLNs are often removed surgically, and therapeutic vaccines against tumor antigens are typically administered systemically or in non-tumor-associated sites. Although the tdLN is immune-suppressed, it is also antigen experienced through drainage of tumor-associated antigens (TAA), so we asked whether therapeutic vaccines targeting the tdLN would be more or less effective than those targeting the non-tdLN. Using LN-targeting nanoparticle (NP)-conjugate vaccines consisting of TAA-NP and CpG-NP, we compared delivery to the tdLN versus non-tdLN in two different cancer models, E.G7-OVA lymphoma (expressing the nonendogenous TAA ovalbumin) and B16-F10 melanoma. Surprisingly, despite the immune-suppressed state of the tdLN, tdLN-targeting vaccination induced substantially stronger cytotoxic CD8+ T-cell responses, both locally and systemically, than non-tdLN-targeting vaccination, leading to enhanced tumor regression and host survival. This improved tumor regression correlated with a shift in the tumor-infiltrating leukocyte repertoire toward a less suppressive and more immunogenic balance. Nanoparticle coupling of adjuvant and antigen was required for effective tdLN targeting, as nanoparticle coupling dramatically increased the delivery of antigen and adjuvant to LN-resident antigen-presenting cells, thereby increasing therapeutic efficacy. This work highlights the tdLN as a target for cancer immunotherapy and shows how its antigen-experienced but immune-suppressed state can be reprogrammed with a targeted vaccine yielding antitumor immunity.

Selective inhibition of CTL activation by a dipalmitoyl-phospholipid that prevents the recruitment of signaling molecules to lipid rafts.

Antigen-specific T-cell activation implicates a redistribution of plasma membrane-bound molecules in lipid rafts, such as the coreceptors CD8 and CD4, the Src kinases Lek and Fyn, and the linker for activation of T cells (LAT), that results in the formation of signaling complexes. These molecules partition in lipid rafts because of palmitoylation of cytoplasmic, membrane proximal cysteines, which is essential for their functional integrity in T-cell activation. Here, we show that exogenous dipalmitoyl-phosphatidylethanolamine (DPPE), but not the related unsaturated dioleoyl-phosphatidylethanolamine (DOPE), partitions in lipid rafts. DPPE inhibits activation of CD8(+) T lymphocytes by sensitized syngeneic antigen-presenting cells or specific major histocompatibility complex (MHC) peptide tetramers, as indicated by esterase release and intracellular calcium mobilization. Cytotoxic, T lymphocyte (CTL)-target cell conjugate formation is not affected by DPPE, indicating that engagement of the T-cell receptor by its cognate ligand is intact in lipid-treated cells. In contrast to other agents known to block raft-dependent signaling, DPPE efficiently inhibits the MHC peptide-induced recruitment of palmitoylated signaling molecules to lipid rafts and CTL activation without affecting cell viability or lipid raft integrity.

Timing is everything: dendritic cell subsets in murine Leishmania infection.

Mouse models of Leishmania major infection have shown that a predominant CD4(+) T helper type 1 cell (Th1) response leads to protection, while T helper type 2 cell (Th2) predominance confers susceptibility. Dendritic cells (DCs) are antigen-presenting cells that orchestrate the T cell response. The immune response to L. major involves direct antigen presentation by migrating DCs or transfer of antigens to resident DCs to prime T cells. In this review, we discuss the timing and consequences of antigen presentation by DC subsets and how this affects Leishmania susceptibility. We propose a model where dermal DCs and Langerhans cells play a role early in infection, followed by inflammatory monocyte-derived DC and lymph node (LN)-resident DCs at later time points of infection to establish the resistant Th1 response.

Review article: Intestinal epithelia and barrier functions.

The mucosal epithelia of the digestive tract acts as a selective barrier, permeable to ions, small molecules and macromolecules. These epithelial cells aid the digestion of food and absorption of nutrients. They contribute to the protection against pathogens and undergo continuous cell renewal which facilitates the elimination of damaged cells. Both innate and adaptive defence mechanisms protect the gastrointestinal-mucosal surfaces against pathogens. Interaction of microorganisms with epithelial cells triggers a host response by activating specific transcription factors which control the expression of chemokines and cytokines. This host response is characterized by the recruitment of macrophages and neutrophils at the site of infection. Disruption of epithelial signalling pathways that recruit migratory immune cells results in a chronic inflammatory response. The adaptive defence mechanism relies on the collaboration of epithelial cells (resident sampling system) with antigen-presenting and lymphoid cells (migratory sampling system); in order to obtain samples of foreign antigen, these samples must be transported across the barriers without affecting the integrity of the barrier. These sampling systems are regulated by both environmental and host factors. Fates of the antigen may differ depending on the way in which they cross the epithelial barrier, i.e. via interaction with motile dendritic cells or epithelial M cells in the follicle-associated epithelium.

Degradation of ZAP-70 following antigenic stimulation in human T lymphocytes: role of calpain proteolytic pathway.

T cell activation by the specific Ag results in dramatic changes of the T cell phenotype that include a rapid and profound down-regulation and degradation of triggered TCRs. In this work, we investigated the fate of the TCR-associated ZAP-70 kinase in Ag-stimulated T cells. T cells stimulated by peptide-pulsed APCs undergo an Ag dose-dependent decrease of the total cellular content of ZAP-70, as detected by FACS analysis and confocal microscopy on fixed and permeabilized T cell-APC conjugates and by Western blot on total cell lysates. The time course of ZAP-70 consumption overlaps with that of zeta-chain degradation, indicating that ZAP-70 is degraded in parallel with TCR internalization and degradation. Pharmacological activation of protein kinase C (PKC) does not induce ZAP-70 degradation, which, on the contrary, requires activation of protein tyrosine kinases. Two lines of evidence indicate that the Ca2+-dependent cysteine protease calpain plays a major role in initiating ZAP-70 degradation: 1) treatment of T cells with cell-permeating inhibitors of calpain markedly reduces ZAP-70 degradation; 2) ZAP-70 is cleaved in vitro by calpain. Our results show that, in the course of T cell-APC cognate interaction, ZAP-70 is rapidly degraded via a calpain-dependent mechanism.

Interferon-gamma impacts at multiple points during the progression of autoimmune diabetes.

The role of interferon-gamma in autoimmune diabetes was assessed by breeding a null mutation of the interferon-gamma receptor alpha chain into the nonobese diabetic mouse strain, as well as into a simplified T cell receptor transgenic model of diabetes. In contrast to a previous report on abrogation of the interferon-gamma gene, mutation of the gene encoding its receptor led to drastic effects on disease in both mouse lines. Nonobese diabetic mice showed a marked inhibition of insulitis-both the kinetics and penetrance-and no signs of diabetes; the transgenic model exhibited near-normal insulitis, but this never evolved into diabetes, either spontaneously or after experimental provocation. This failure could not be explained by perturbations in the ratio of T helper cell phenotypes; rather, it reflected a defect in antigen-presenting cells or in the islet beta cell targets.