Dendritic cells induce autoimmune diabetes and maintain disease via de novo formation of local lymphoid tissue

Aligning cellular and molecular components in age-dependent tertiary lymphoid tissues of kidney and liver

Tertiary lymphoid tissues (TLTs) are ectopic lymphoid structures induced by multiple stimuli, including infection and tissue injuries; however, their clinical relevance in disease progression has remained unclear. We demonstrated previously that TLTs develop in mouse and human kidneys with aging and can be a potential marker of kidney injury and prognosis, and therapeutic targets. In addition, we found that two types of unique lymphocytes that emerge with aging, senescence-associated T cells and age-associated B cells, are essential for TLT formation in the kidney. Although TLTs develop with aging in other organs as well, their cellular and molecular components, and clinical significance remain unclear. In the present study, we found that TLTs developed in the liver with aging, and that their cellular and molecular components were similar to those in the kidneys. Notably, senescence-associated T cells and age-associated B cells were also present in hepatic TLTs. Furthermore, analysis of publicly available data on human liver biopsy transcriptomes revealed that the expression of TLT-related genes was elevated in the liver biopsy samples from hepatitis C virus (HCV)-infected patients compared with those without HCV infection and was associated with liver injury and fibrosis. Therefore, we analyzed liver biopsy samples from 47 HCV patients and found that TLTs were present in 87.2% of cases and that the numbers and stages of TLTs were higher in aged patients and cellular and molecular components of TLTs in humans were similar to those in mice. Our findings suggesting that age-dependent TLT formation is a systemic phenomenon across the tissues and aging is also a predisposing factor for TLT formation across organs.

Sustained innate interferon is an essential inducer of tertiary lymphoid structures

Tertiary lymphoid structures (TLS) resemble follicles of secondary lymphoid organs and develop in nonlymphoid tissues during inflammation and cancer. Which cell types and signals drive the development of TLS is largely unknown. To investigate early events of TLS development in the lungs, we repeatedly instilled p(I:C) plus ovalbumin (Ova) intranasally. This induced TLS ranging from lymphocytic aggregates to organized and functional structures containing germinal centers. We found that TLS development is independent of FAP+ fibroblasts, alveolar macrophages, or CCL19 but crucially depends on type I interferon (IFN-I). Mechanistically, IFN-I initiates two synergistic pathways that culminate in the development of TLS. On the one hand, IFN-I induces lymphotoxin (LT)α in lymphoid cells, which stimulate stromal cells to produce the B-cell-attracting chemokine CXCL13 through LTβR-signaling. On the other hand, IFN-I is sensed by stromal cells that produce the T-cell-attracting chemokines CXCL9, CXCL10 as well as CCL19 and CCL21 independently of LTβR. Consequently, B-cell aggregates develop within a week, whereas follicular dendritic cells and germinal centers appear after 3 weeks. Thus, sustained production of IFN-I together with an antigen is essential for the induction of functional TLS in the lungs.

CD4+ Cytotoxic T Cells Involved in the Development of EBV-Associated Diseases

Activated cytotoxic CD4 T cells (HLA-DR+) play an important role in the control of EBV infection, especially in cells with latency I (EBNA-1). One of the evasion mechanisms of these latency cells is generated by gp42, which, via peripherally binding to the β1 domain of the β chain of MHC class II (HLA-DQ, -DR, and -DP) of the infected B lymphocyte, can block/alter the HLA class II/T-cell receptor (TCR) interaction, and confer an increased level of susceptibility towards the development of EBV-associated autoimmune diseases or cancer in genetically predisposed individuals (HLA-DRB1* and DQB1* alleles). The main developments predisposing the factors of these diseases are: EBV infection; HLA class II risk alleles; sex; and tissue that is infiltrated with EBV-latent cells, forming ectopic lymphoid structures. Therefore, there is a need to identify treatments for eliminating cells with EBV latency, because the current treatments (e.g., antivirals and rituximab) are ineffective.

Stromal and Immune Cell Dynamics in Tumor Associated Tertiary Lymphoid Structures and Anti-Tumor Immune Responses

Tertiary lymphoid structures (TLS) are ectopic lymphoid organs that have been observed in chronic inflammatory conditions including cancer, where they are thought to exert a positive effect on prognosis. Both immune and non-immune cells participate in the genesis of TLS by establishing complex cross-talks requiring both soluble factors and cell-to-cell contact. Several immune cell types, including T follicular helper cells (Tfh), regulatory T cells (Tregs), and myeloid cells, may accumulate in TLS, possibly promoting or inhibiting their development. In this manuscript, we propose to review the available evidence regarding specific aspects of the TLS formation in solid cancers, including 1) the role of stromal cell composition and architecture in the recruitment of specific immune subpopulations and the formation of immune cell aggregates; 2) the contribution of the myeloid compartment (macrophages and neutrophils) to the development of antibody responses and the TLS formation; 3) the immunological and metabolic mechanisms dictating recruitment, expansion and plasticity of Tregs into T follicular regulatory cells, which are potentially sensitive to immunotherapeutic strategies directed to costimulatory receptors or checkpoint molecules.

High endothelial venules (HEVs) in immunity, inflammation and cancer

High endothelial venules (HEVs) are specialized blood vessels mediating lymphocyte trafficking to lymph nodes (LNs) and other secondary lymphoid organs. By supporting high levels of lymphocyte extravasation from the blood, HEVs play an essential role in lymphocyte recirculation and immune surveillance for foreign invaders (bacterial and viral infections) and alterations in the body’s own cells (neoantigens in cancer). The HEV network expands during inflammation in immune-stimulated LNs and is profoundly remodeled in metastatic and tumor-draining LNs. HEV-like blood vessels expressing high levels of the HEV-specific sulfated MECA-79 antigens are induced in non-lymphoid tissues at sites of chronic inflammation in many human inflammatory and allergic diseases, including rheumatoid arthritis, Crohn’s disease, allergic rhinitis and asthma. Such vessels are believed to contribute to the amplification and maintenance of chronic inflammation. MECA-79⁺ tumor-associated HEVs (TA-HEVs) are frequently found in human tumors in CD3⁺ T cell-rich areas or CD20⁺ B-cell rich tertiary lymphoid structures (TLSs). TA-HEVs have been proposed to play important roles in lymphocyte entry into tumors, a process essential for successful antitumor immunity and lymphocyte-mediated cancer immunotherapy with immune checkpoint inhibitors, vaccines or adoptive T cell therapy. In this review, we highlight the phenotype and function of HEVs in homeostatic, inflamed and tumor-draining lymph nodes, and those of HEV-like blood vessels in chronic inflammatory diseases. Furthermore, we discuss the role and regulation of TA-HEVs in human cancer and mouse tumor models.

Priming of myelin-specific T cells in the absence of dendritic cells results in accelerated development of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an established animal model of multiple sclerosis (MS). Inflammatory CD4+ T cell responses directed against CNS antigens, including myelin proteolipid protein (PLP), are key mediators of EAE. Dendritic cells (DCs) are critical for the induction of T cell responses against infectious agents. However, the importance of DCs in priming self-reactive CD4+ T cells in autoimmune disease such as MS has been unclear. To determine the requirement of DCs in PLP-specific CD4+ T cell responses and EAE, we genetically deleted CD11c+ DCs in PLP T cell receptor (TCR) transgenic SJL mice constitutively. DC deficiency did not impair the development, selection or the pathogenic function of PLP-specific CD4+ T cells in these mice, and resulted in accelerated spontaneous EAE compared to DC sufficient controls. In addition, using a genetic approach to ablate DCs conditionally in SJL mice, we show that CD11c+ DCs were dispensable for presenting exogenous or endogenous myelin antigen to PLP-specific T cells and for promoting pro-inflammatory T cell responses and severe EAE. Our findings demonstrate that constitutive or conditional ablation of CD11c+ DCs diminished self-tolerance to PLP autoantigen. They further show that in the absence of DCs, non-DCs can efficiently present CNS myelin antigens such as PLP to self-reactive T cells, resulting in accelerated onset of spontaneous or induced EAE.

Immunopathology of Type 1 Diabetes and Immunomodulatory Effects of Stem Cells: A Narrative Review of the Literature

Type 1 Diabetes (T1D) is a complex autoimmune disorder which occurs as a result of an intricate series of pathologic interactions between pancreatic β-cells and a wide range of components of both the innate and the adaptive immune systems. Stem-cell therapy, a recently-emerged potentially therapeutic option for curative treatment of diabetes, is demonstrated to cause significant alternations to both different immune cells such as macrophages, natural killer (NK) cells, dendritic cells, T cells, and B cells and non-cellular elements including serum cytokines and different components of the complement system. Although there exists overwhelming evidence indicating that the documented therapeutic effects of stem cells on patients with T1D is primarily due to their potential for immune regulation rather than pancreatic tissue regeneration, to date, the precise underlying mechanisms remain obscure. On the other hand, immune-mediated rejection of stem cells remains one of the main obstacles to regenerative medicine. Moreover, the consequences of efferocytosis of stem-cells by the recipients' lung-resident macrophages have recently emerged as a responsible mechanism for some immune-mediated therapeutic effects of stem-cells. This review focuses on the nature of the interactions amongst different compartments of the immune systems which are involved in the pathogenesis of T1D and provides explanation as to how stem cell-based interventions can influence immune system and maintain the physiologic equilibrium.

Distorted frequency of dendritic cells and their associated stimulatory and inhibitory markers augment the pathogenesis of pemphigus vulgaris

The objective of this study was to investigate the frequency and functionality of DCs and its associated stimulatory and inhibitory markers in the pathogenesis of PV Active PV patients (n = 30) having both skin and oral lesions, and 30 healthy controls were recruited in the study. The frequency of DCs was determined by flow cytometry followed by the primary culture by using recombinant IL-4 (250 IU/ml) and GM-CSF (600 IU/ml). The culture supernatant was used for ELISA. RNA was isolated from sorted DCs and used for the mRNA expression of DC-associated stimulatory (CD40 and CD80) and inhibitory (PSGL1 and ILT3) markers. Tissue localization of Langerhans cells was done by immunohistochemistry. In this study, altered frequency of myeloid DC (mDC) and plasmacytoid DC (pDC) was seen in the circulation of PV patients. The primary culture of patient-derived DCs showed anomalous cytokine profiling. In the culture supernatant of DCs, elevated levels of TNF-ɑ and IL-12 were detected in PV patients. Meanwhile, reverse trend was found in the case of IFN-ɑ and IL-10 cytokine levels. Similarly, a discrepancy in the expression of DC-associated stimulatory (CD40 and CD80) and inhibitory (PSGL1 and ILT3) markers suggested their possible involvement in the immunopathogenesis of PV. An elevated number of tissue localizing Langerhans cells was also observed in the perilesional skin. This study indicates the distorted frequency and functionality of DCs in the immunopathogenesis of PV. Targeting these functional markers in the future may generate novel therapeutic options for better management of PV.

Tertiary Lymphoid Organs: A Primer for Otolaryngologists

OBJECTIVES/HYPOTHESIS

Lymphoid neogenesis or the development of organised, de novo lymphoid structures has been described increasingly in chronically inflamed tissues. The presence of tertiary lymphoid organs (TLOs) has already been demonstrated to result in significant consequences for disease pathology, severity, prognosis and patient outcomes. Whilst the wider medical community has embraced TLOs as important markers of disease and potential therapeutic targets, the otolaryngology field has only begun turning to these entities in an academic capacity. This review aims to outline the role of tertiary lymphoid organs in disease and summarise key early findings in the ENT field. We also an overview of TLOs, their developmental process and clinicopathological implications.

STUDY DESIGN

Literature review.

METHODS

A literature search for all relevant peer-reviewed publications pertaining to TLOs and ENT diseases. Search was conducted using PubMed, Embase and CINAHL databases.

RESULTS

A total of 24 studies were identified relevant to the topic. The majority of TLO research in ENT fell into the areas of oral squamous cell carcinoma (SCC) and chronic rhinosinusitis (CRS).

CONCLUSIONS

Early research into both oral SCC and CRS suggests that TLOs have significant roles within ear, nose and throat (ENT) diseases. At this point in time, however, TLOs remain somewhat a mystery amongst otolaryngologists. As information in this field increases, we may develop a better understanding of how lymphoid neogenesis can influence disease outcomes amongst our patients and, ultimately, how they can be utilised in an immunotherapeutic manner. Laryngoscope, 131:1697-1703, 2021.

Chronic Inflammation: A Common Promoter in Tertiary Lymphoid Organ Neogenesis

Tertiary lymphoid organs (TLOs) frequently develop locally in adults in response to non-resolving inflammation. Chronic inflammation leads to the differentiation of stromal fibroblast cells toward lymphoid tissue organizer-like cells, which interact with lymphotoxin α1β2+ immune cells. The interaction initiates lymphoid neogenesis by recruiting immune cells to the site of inflammation and ultimately leads to the formation of TLOs. Mature TLOs harbor a segregated T-cell zone, B-cell follicles with an activated germinal center, follicular dendritic cells, and high endothelial venules, which architecturally resemble those in secondary lymphoid organs. Since CXCL13 and LTα₁β₂ play key roles in TLO neogenesis, they might constitute potential biomarkers of TLO activity. The well-developed TLOs actively regulate local immune responses and influence disease progression, and they are thereby regarded as the powerhouses of local immunity. In this review, we recapitulated the determinants for TLOs development, with great emphasis on the fundamental role of chronic inflammation and tissue-resident stromal cells for TLO neogenesis, hence offering guidance for therapeutic interventions in TLO-associated diseases.

Blueberry supplementation attenuates oxidative stress within monocytes and modulates immune cell levels in adults with metabolic syndrome: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Blueberries (BB) have been shown to improve insulin sensitivity and endothelial function in obese and pre-diabetic humans, and decrease oxidative stress and inflammation, and ameliorate cardio-renal damage in rodents. This indicates that blueberries have a systemic effect and are not limited to a particular organ system. In order for blueberries to exert beneficial effects on the whole body, the mechanism would logically have to operate through modulation of cellular humoral factors.

OBJECTIVE

This study investigated the role of blueberries in modulating immune cell levels and attenuating circulatory and monocyte inflammation and oxidative stress in metabolic syndrome (MetS) subjects.

DESIGN

A double-blind, randomized and placebo-controlled study was conducted in adults with MetS, in which they received a blueberry (22.5 g freeze-dried) or placebo smoothie twice daily for six weeks. Free radical production in the whole blood and monocytes, dendritic cell (DC) levels, expression of cytokines in monocytes and serum inflammatory markers were assessed pre- and post-intervention.

RESULTS

Baseline free radical levels in MetS subjects' samples were not different between groups. Treatment with blueberries markedly decreased superoxide and total reactive oxygen species (ROS) in whole blood and monocytes compared to the placebo (p ≤ 0.05). The baseline DC numbers in MetS subjects' samples in both groups were not different, however treatment with blueberries significantly increased myeloid DC (p ≤ 0.05) and had no effect on plasmacytoid cells. Blueberry treatment decreased monocyte gene expression of TNFα, IL-6, TLR4 and reduced serum GMCSF in MetS subjects when compared to the placebo treatment (p ≤ 0.05).

CONCLUSIONS

The findings of the current study demonstrate that blueberries exert immunomodulatory effects and attenuate oxidative stress and inflammation in adults with MetS.

A methodological review of induced animal models of autoimmune diseases

Autoimmune disorders are characterized by a loss of immune tolerance and consequent autoimmunity-mediated disease manifestation. Experimental models are invaluable research tools helping us to understand disease pathogenesis and to search for novel therapeutics. Animal models of autoimmune diseases consist of two groups, spontaneous and induced models. In this review article, we focus on the induced models of autoimmune diseases. Due to the complex nature of autoimmune disorders, many strategies have been applied for the induction of corresponding experimental models in animals like monkeys, rabbits, rats, and mice. Methodologically, these strategies can be categorized into three categories, namely immunization with autoantigen, transfer of autoimmunity, and induction by environmental factors. In this review article, we aim to provide a comprehensive overview of the field of induced experimental autoimmune diseases. On the one hand, we describe and summarize the different strategies used for induction of experimental autoimmune disease. On the other hand, we discuss how to select a strategy for modeling human disease, including the choice of an appropriate species and method for such an approach.

Tertiary Lymphoid Structures Among the World of Noncanonical Ectopic Lymphoid Organizations

Tertiary lymphoid structures (TLOs), also known as ectopic lymphoid structures, are associated with chronic infections and inflammatory diseases. Despite their association with pathology, these structures are actually a normal, albeit transient, component of the immune system and facilitate local immune responses that are meant to mitigate inflammation and resolve infection. Many of the mechanisms controlling the formation and function of tertiary lymphoid structures have been identified, in part by experimentally triggering their formation using defined stimuli under controlled conditions. Here, we introduce the experimental and pathological conditions in which tertiary lymphoid tissues are formed, describe the mechanisms linked to their formation, and discuss their functions in the context of both infection and inflammation.

Modelling of Experimental Infections

This chapter aims to give a clear idea of how mathematical analysis for experimental systems could help in the process of data assimilation, parameter estimation and hypothesis testing.

Modulation of the immune response in rheumatoid arthritis with strategically released rapamycin

Rheumatoid arthritis (RA) is a chronic inflammatory disease, which is associated with symptoms, including synovial membrane inflammatory pain, joint synovitis and stiffness. However, there are no effective methods available to cure this disease. In the present study, rapamycin was used to modulate immunity in RA. To limit the cytotoxicity of rapamycin, rapamycin was loaded into well-characterized biocompatible nanoparticles. In vitro, rapamycin particles downregulated the activation of dendritic cell surface markers, including CD80⁺ and CD40⁺, upon interacting with macrophages. The rapamycin particles reduced the secretion of inflammatory cytokines, including interleukin (IL)-6, tumor necrosis factor (TNF) and IL-1β, which are characteristic of RA. In vivo, the rapamycin particles decreased the symptoms of RA in mice, and the production of inflammatory cytokines was associated with the occurrence of RA. The present study partially revealed the interactions between rapamycin and two types of immune cell in RA disease, and may potentially offer a solution to improve the treatment of RA.

Tertiary lymphoid organs in systemic autoimmune diseases: pathogenic or protective?

Tertiary lymphoid organs are found at sites of chronic inflammation in autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. These organized accumulations of T and B cells resemble secondary lymphoid organs and generate autoreactive effector cells. However, whether they contribute to disease pathogenesis or have protective functions is unclear. Here, we discuss how tertiary lymphoid organs can generate potentially pathogenic cells but may also limit the extent of the response and damage in autoimmune disease.

Mechanisms of diabetic autoimmunity: I--the inductive interface between islets and the immune system at onset of inflammation

The mechanisms of autoimmune reactivity onset in type 1 diabetes (T1D) remain elusive despite extensive experimentation and discussion. We reconsider several key aspects of the early stages of autoimmunity at four levels: islets, pancreatic lymph nodes, thymic function and peripheral immune homeostasis. Antigen presentation is the islets and has the capacity to provoke immune sensitization, either in the process of physiological neonatal β cell apoptosis or as a consequence of cytolytic activity of self-reactive thymocytes that escaped negative regulation. Diabetogenic effectors are efficiently expanded in both the islets and the lymph nodes under conditions of empty lymphoid niches during a period of time coinciding with a synchronized wave of β cell apoptosis surrounding weaning. A major drive of effector cell activation and expansion is inherent peripheral lymphopenia characteristic of neonates, though it remains unclear when is autoimmunity triggered in subjects displaying hyperglycemia in late adolescence. Our analysis suggests that T1D evolves through coordinated activity of multiple physiological mechanisms of stimulation within specific characteristics of the neonate immune system.

Growth of Murine Splenic Tissue Is Suppressed by Lymphotoxin β-Receptor Signaling (LTβR) Originating from Splenic and Non-Splenic Tissues

Development and maintenance of secondary lymphoid organs such as lymph nodes and spleen essentially depend on lymphotoxin β-receptor (LTβR) signaling. It is unclear, however, by which molecular mechanism their size is limited. Here, we investigate whether the LTβR pathway is also growth suppressing. By using splenic tissue transplantation it is possible to analyze a potential contribution of LTβR signaling inside and outside of the implanted tissue. We show that LTβR signaling within the endogenous spleen and within non-splenic tissues both significantly suppressed the regeneration of implanted splenic tissue. The suppressive activity positively correlated with the total number of LTβR expressing cells in the animal (regenerate weights of 115 ± 8 mg in LTβR deficient recipients and of 12 ± 9 mg in wild-type recipients), affected also developed splenic tissue, and was induced but not executed via LTβR signaling. Two-dimensional differential gel electrophoresis and subsequent mass spectrometry of stromal splenic tissue was applied to screen for potential factors mediating the LTβR dependent suppressive activity. Thus, LTβR dependent growth suppression is involved in regulating the size of secondary lymphoid organs, and might be therapeutically used to eradicate tertiary lymphoid tissues during autoimmune diseases.

Antigen-Presenting Cells and Antigen Presentation in Tertiary Lymphoid Organs

Tertiary lymphoid organs (TLOs) form in territorialized niches of peripheral tissues characterized by the presence of antigens; however, little is known about mechanism(s) of antigen handling by ectopic lymphoid structures. In this mini review, we will discuss the role of antigen-presenting cells and mechanisms of antigen presentation in TLOs, summarizing what is currently known about this facet of the formation and function of these tissues as well as identifying questions yet to be addressed.

Analysis of the cell populations composing the mononuclear cell infiltrates in the labial minor salivary glands from patients with rheumatoid arthritis and sicca syndrome

OBJECTIVES

Sicca symptoms occur in around 30% of rheumatoid arthritis (RA) patients. Herein, we examined the characteristics of RA patients bearing sicca symptomatology (RA-sicca) with a special focus on the immunohistopathological features of their labial minor salivary gland (LMSG) biopsies.

METHODS

Our cohort included 100 consecutive RA patients which were interrogated using a sicca symptoms questionnaire. Positive responders were evaluated for ocular and oral dryness and underwent an LMSG biopsy. All samples were immunohistochemically evaluated for the presence and distribution of specific leukocyte subsets using appropriate markers and for the expression of certain immunoregulatory molecules by salivary gland epithelial cells. Positively stained and total mononuclear cells (MNC) were counted in the entire section. Counts were expressed as cell frequency (percentage of cell type number/total infiltrating MNC number).

RESULTS

In the majority (86.1%) of the 44 RA-sicca cases, periductal infiltrates were observed in LMSG biopsies. The frequencies of infiltrating cell subtypes and their correlation with lesion severity were different from that previously described in primary Sjögren's syndrome (pSS). Moreover, DCs and ΜΦs frequencies were increased in RA-sicca patients who had a biopsy focus score <1 and absence of anti-Ro/anti-La autoantibodies, in contrast to what was observed for B cells. In about half of the biopsies, salivary gland epithelial cells expressed CD80/B7.1 molecules, most commonly in patients with a positive biopsy or anti-Ro/anti-La autoantibodies.

CONCLUSION

LMSG infiltrates composition in RA-sicca patients is distinct from that described in pSS. These differences, further attest to diverse pathophysiologic processes operating in these two entities.

Early IL-1 Signaling Promotes iBALT Induction after Influenza Virus Infection

Inducible bronchus-associated lymphoid tissue (iBALT) is a long lasting tertiary lymphoid tissue that can be induced following influenza A virus (IAV) infection. Previous studies have shown that iBALT structures containing germinal center (GC) B cells protect against repeated infection by contributing locally to the cellular and humoral immune response. If we are to exploit this in vaccination strategies, we need a better understanding on how iBALT structures are induced. One hypothesis is that the strength of the initial innate response dictates induction of iBALT. In the present study, we investigated the role of interleukin (IL)-1 and IL-1R signaling on iBALT formation. Mice lacking the IL-1R had a delayed viral clearance and, thus, a prolonged exposure to viral replication, leading to increased disease severity, compared to wild-type mice. Contradictorily, iBALT formation following clearance of the virus was heavily compromised in Il1r1^−/− mice. Quantification of gene induction after IAV infection demonstrated induction of IL-1α and to a much lesser extent of IL-1β. Administration of recombinant IL-1α to the lungs of wild-type mice, early but not late, after IAV infection led to more pronounced iBALT formation and an increased amount of GC B cells in the lungs. Bone marrow chimeric mice identified the stromal compartment as the crucial IL-1 responsive cell for iBALT induction. Mechanistically, Q-PCR analysis of lung homogenates revealed a strongly diminished production of CXCL13, a B cell-attracting chemokine, in Il1r^−/− mice during the early innate phase of IAV infection. These experiments demonstrate that appropriate innate IL-1α–IL-1R signaling is necessary for IAV clearance and at the same time instructs the formation of organized tertiary lymphoid tissues through induction of CXCL13 early after infection. These findings are discussed in the light of recent insights on the pathogenesis of tertiary lymphoid organ formation in the lung in various diseases where the IL-1 axis is hyperactive, such as rheumatoid arthritis and COPD.

RORγt Expression and Lymphoid Neogenesis in the Brain of Patients with Secondary Progressive Multiple Sclerosis

Ectopic B-cell follicle-like structures (ELS) are found in the meninges of patients with secondary progressive multiple sclerosis (SPMS). Because cells expressing the transcriptional regulator retinoic acid receptor-related orphan receptor-γt (RORγt) and producing interleukin 17 (IL17), e.g. T helper 17 cells and lymphoid tissue inducer (LTi) cells, have been implicated in the formation of ELS, we studied RORγt and IL17 expression in brain tissue from patients with SPMS an assessed their relationships to immune infiltrates and meningeal ELS. By immunohistochemistry, small numbers of RORγt-positive cells were detected in the meninges of 6 of 12 SPMS cases analyzed. RORγt-positive cells were localized in B-cell follicles or aggregates and nearby diffuse meningeal infiltrates, and predominantly co-expressed CD3. Only a few RORγt-positive, CD3-negative cells were observed, suggesting the presence of group 3 innate lymphoid cells, which comprise the LTi cell subset. Some IL17-positive cells, co-expressing in part RORγt and predominantly CD3, were found in meningeal B-cell follicles from 4 SPMS cases. Rare RORγt-positive and IL17-positive cells were detected in white matter. Gene expression analysis of laser dissected meningeal infiltrates and white matter lesions confirmed low frequencies and virtual absence of RORγt and IL17 signals, respectively. Thus, there is selective migration or survival of RORγt-positive cells in MS patient meninges and an association of these cells with ELS.

Piperlongumine Suppresses Dendritic Cell Maturation by Reducing Production of Reactive Oxygen Species and Has Therapeutic Potential for Rheumatoid Arthritis

Piperlongumine (PLM) is a natural product from the plant Piper longum that inhibits platelet aggregation, atherosclerosis plaque formation, and tumor cell growth. It has potential value in immunomodulation and the management of autoimmune diseases. In this study, we investigated the role of PLM in regulating the differentiation and maturation of dendritic cells (DCs), a critical regulator of immune tolerance, and evaluated its clinical effects in a rheumatoid arthritis mouse model. We found that PLM treatment reduced LPS-induced murine bone marrow-derived DC maturation, characterized by reduced expression of CD80/86, secretion of MCP-1, IL-12p70, IL-6, TNFα, IFN-γ, and IL-23, and reduced alloproliferation of T cells; however, PLM does not affect cell differentiation. Furthermore, PLM reduced intracellular reactive oxygen species (ROS) production by DCs and inhibited the activation of p38, JNK, NF-κB, and PI3K/Akt signaling pathways. Conversely, PLM increased the expression of GSTP1 and carbonyl reductase 1, two enzymes that counteract ROS effects. ROS inhibition by exogenous N-acetyl-l-cysteine suppressed DC maturation. PLM treatment improved the severity of arthritis and reduced in vivo splenic DC maturation, collagen-specific CD4(+) T cell responses, and ROS production in mice with collagen-induced arthritis. Taken together, these results suggest that PLM inhibits DC maturation by reducing intracellular ROS production and has potential as a therapeutic agent for rheumatoid arthritis.

Mechanisms of autoimmunity in the non-obese diabetic mouse: effector/regulatory cell equilibrium during peak inflammation

Immune imbalance in autoimmune disorders such as type 1 diabetes may originate from aberrant activities of effector cells or dysfunction of suppressor cells. All possible defective mechanisms have been proposed for diabetes-prone species: (i) quantitative dominance of diabetogenic cells and decreased numbers of regulatory T cells, (ii) excessive aggression of effectors and defective function of suppressors, (iii) perturbed interaction between effector and suppressor cells, and (iv) variations in sensitivity to negative regulation. The experimental evidence available to date presents conflicting information on these mechanisms, with identification of perturbed equilibrium on the one hand and negation of critical role of each mechanism in propagation of diabetic autoimmunity on the other hand. In our analysis, there is no evidence that inherent abnormalities in numbers and function of effector and suppressor T cells are responsible for the immune imbalance responsible for propagation of type 1 diabetes as a chronic inflammatory process. Possibly, the experimental tools for investigation of these features of immune activity are still underdeveloped and lack sufficient resolution, in the presence of the extensive biological viability and functional versatility of effector and suppressor elements.

Reg3g overexpression promotes β cell regeneration and induces immune tolerance in nonobese-diabetic mouse model

The regenerating islet-derived gene was first isolated in regenerated pancreas tissues, greatly contributing to β cell regeneration. It is an anti-inflammatory in response to cellular stress. This encouraged us to investigate the exact role of a novel member of Reg family, regenerating islet-derived gene γ, in type 1 diabetes of nonobese-diabetic mice. For this, Reg3g gene was overexpressed in pancreatic islets, and conferred beneficial effects on β cell regeneration through activating the Janus kinase 2/signal transducer and activator of transcription 3/nuclear factor κB signaling pathway. Lentiviral vector-encoding regenerating islet-derived gene γ treatment also decreased lymphocyte infiltrates of the intra-islet and peri-islet by inducing both differentiation of regulatory T cell and immature dendritic cells of tolerogenic properties, which attenuated autoimmunity. This treatment further contributed to rebalanced levels of type 1/2 helper T cell cytokines and elevated α1-antitrypsin levels in the serum. These results were not observed in phosphate-buffered saline-treated mice or in lentivirus-control mice. We have shown, for the first time, to our knowledge, that regenerating islet-derived gene γ promotes β cell regeneration and preserves β cells from autoimmunity damage by increasing regulatory T cell differentiation and inducing tolerated dendritic cells. This regenerating islet-derived gene γ infusion could probably be developed into an optimal gene therapy for the prevention and reversal of type 1 diabetes.

Ectopic lymphoid follicles: inducible centres for generating antigen-specific immune responses within tissues

Lymphoid neogenesis is traditionally viewed as a pre‐programmed process that promotes the formation of lymphoid organs during development. Here, the spatial organization of T and B cells in lymph nodes and spleen into discrete structures regulates antigen‐specific responses and adaptive immunity following immune challenge. However, lymphoid neogenesis is also triggered by chronic or persistent inflammation. Here, ectopic (or tertiary) lymphoid organs frequently develop in inflamed tissues as a response to infection, auto‐immunity, transplantation, cancer or environmental irritants. Although these structures affect local immune responses, the contribution of these lymphoid aggregates to the underlining pathology are highly context dependent and can elicit either protective or deleterious outcomes. Here we review the cellular and molecular mechanisms responsible for ectopic lymphoid neogenesis and consider the relevance of these structures in human disease.

Discovery of Intermediary Genes between Pathways Using Sparse Regression

The use of pathways and gene interaction networks for the analysis of differential expression experiments has allowed us to highlight the differences in gene expression profiles between samples in a systems biology perspective. The usefulness and accuracy of pathway analysis critically depend on our understanding of how genes interact with one another. That knowledge is continuously improving due to advances in next generation sequencing technologies and in computational methods. While most approaches treat each of them as independent entities, pathways actually coordinate to perform essential functions in a cell. In this work, we propose a methodology based on a sparse regression approach to find genes that act as intermediary to and interact with two pathways. We model each gene in a pathway using a set of predictor genes, and a connection is formed between the pathway gene and a predictor gene if the sparse regression coefficient corresponding to the predictor gene is non-zero. A predictor gene is a shared neighbor gene of two pathways if it is connected to at least one gene in each pathway. We compare the sparse regression approach to Weighted Correlation Network Analysis and a correlation distance based approach using time-course RNA-Seq data for dendritic cell from wild type, MyD88-knockout, and TRIF-knockout mice, and a set of RNA-Seq data from 60 Caucasian individuals. For the sparse regression approach, we found overrepresented functions for shared neighbor genes between TLR-signaling pathway and antigen processing and presentation, apoptosis, and Jak-Stat pathways that are supported by prior research, and compares favorably to Weighted Correlation Network Analysis in cases where the gene association signals are weak.

Generation of antigen-specific Foxp3+ regulatory T-cells in vivo following administration of diabetes-reversing tolerogenic microspheres does not require provision of antigen in the formulation

We have developed novel antisense oligonucleotide-formulated microspheres that can reverse hyperglycemia in newly-onset diabetic mice. Dendritic cells taking up the microspheres adopt a restrained co-stimulation ability and migrate to the pancreatic lymph nodes when injected into an abdominal region that is drained by those lymph nodes. Furthermore, we demonstrate that the absolute numbers of antigen-specific Foxp3+ T regulatory cells are increased only in the lymph nodes draining the site of administration and that these T-cells proliferate independently of antigen supply in the microspheres. Taken together, our data add to the emerging model where antigen supply may not be a requirement in "vaccines" for autoimmune disease, but the site of administration - subserved by lymph nodes draining the target organ - is in fact critical to foster the generation of antigen-specific regulatory cells. The implications of these observations on "vaccine" design for autoimmunity are discussed and summarized.

Ectopic lymphoid-like structures in infection, cancer and autoimmunity

Ectopic lymphoid-like structures often develop at sites of inflammation where they influence the course of infection, autoimmune disease, cancer and transplant rejection. These lymphoid aggregates range from tight clusters of B cells and T cells to highly organized structures that comprise functional germinal centres. Although the mechanisms governing ectopic lymphoid neogenesis in human pathology remain poorly defined, the presence of ectopic lymphoid-like structures within inflamed tissues has been linked to both protective and deleterious outcomes in patients. In this Review, we discuss investigations in both experimental model systems and patient cohorts to provide a perspective on the formation and functions of ectopic lymphoid-like structures in human pathology, with particular reference to the clinical implications and the potential for therapeutic targeting.

Decreased dendritic cell numbers but increased TLR9-mediated interferon-alpha production in first degree relatives of type 1 diabetes patients

OBJECTIVE

Dendritic cells (DCs) play an important role in pathogenesis of autoimmunity, including type 1 diabetes (T1D). In this study, we investigated DC subpopulations and their responses to TLR stimulation in T1D patients and their relatives.

METHODS

We analyzed the frequency of myeloid (mDCs) and plasmacytoid DCs (pDCs) in 97 T1D patients (69 onset, 28 long-term), 67 first-degree relatives, and 64 controls. We additionally tested the IFN-alpha production by pDCs upon stimulation with TLR 7, 8 and 9 agonists.

RESULTS

A lower number of mDCs and pDCs were found in T1D patients and their relatives. Of all the tested TLR ligands, only stimulation with CpG 2216 induced IFN-alpha production that was the highest in T1D relatives, except of autoantibody-negative relatives bearing the protective haplotypes.

CONCLUSION

Our data demonstrate disturbances in DC number and function expressed most significantly in T1D relatives and point to a potential role of TLR9-induced IFN-alpha production in T1D development.

In vivo detection of peripherin-specific autoreactive B cells during type 1 diabetes pathogenesis

Autoreactive B cells are essential for the pathogenesis of type 1 diabetes. The genesis and dynamics of autoreactive B cells remain unknown. In this study, we analyzed the immune response in the NOD mouse model to the neuronal protein peripherin (PRPH), a target Ag of islet-infiltrating B cells. PRPH autoreactive B cells recognized a single linear epitope of this protein, in contrast to the multiple epitope recognition commonly observed during autoreactive B cell responses. Autoantibodies to this epitope were also detected in the disease-resistant NOR and C57BL/6 strains. To specifically detect the accumulation of these B cells, we developed a novel approach, octameric peptide display, to follow the dynamics and localization of anti-PRPH B cells during disease progression. Before extended insulitis was established, anti-PRPH B cells preferentially accumulated in the peritoneum. Anti-PRPH B cells were likewise detected in C57BL/6 mice, albeit at lower frequencies. As disease unfolded in NOD mice, anti-PRPH B cells invaded the islets and increased in number at the peritoneum of diabetic but not prediabetic mice. Isotype-switched B cells were only detected in the peritoneum. Anti-PRPH B cells represent a heterogeneous population composed of both B1 and B2 subsets. In the spleen, anti-PRPH B cell were predominantly in the follicular subset. Therefore, anti-PRPH B cells represent a heterogeneous population that is generated early in life but proliferates as diabetes is established. These findings on the temporal and spatial progression of autoreactive B cells should be relevant for our understanding of B cell function in diabetes pathogenesis.

Tolerogenic dendritic cell vaccines to treat autoimmune diseases: can the unattainable dream turn into reality?

Autoimmune diseases affect about one in 15 individuals in developed countries and are characterized by a breakdown in immune tolerance. Current therapeutic approaches against destructive immune responses in autoimmune diseases are based on non-specific agents systemically suppressing the function of many immune effector cells. This indiscriminate immunosuppression, however, often causes serious and sometimes life-threatening side effects. Therefore, the need for more specific treatments resulting in lower toxicity and longer-term solutions is high. Because of the established role of dendritic cells (DCs) in maintaining the balance between immunity and tolerance, tolerogenic (tol)DCs might be novel therapeutic targets to prevent undesirable (auto-)immune responses. The idea behind tolDC therapy is that it is a highly targeted, antigen-specific treatment that only affects the auto-reactive inflammatory response. The therapeutic potential of tolDCs has already been proven in experimental animal models of different autoimmune disorders as well as with in vitro experiments using ex vivo generated human tolDCs, thus the challenge remains in bringing tolDC therapy to the clinic, although first clinical trials have been conducted. In this review, we will extensively discuss the use of tolDCs for induction of antigen-specific tolerance in several autoimmune disease settings, from bench to bedside, including currently applied strategies to generate tolDCs as well as technical difficulties and challenges in the field.

Role of adaptive and innate immune cells in chronic fatigue syndrome/myalgic encephalomyelitis

Perturbations in immune processes are a hallmark of a number of autoimmune and inflammatory disorders. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is an inflammatory disorder with possible autoimmune correlates, characterized by reduced NK cell activity, elevations in regulatory T cells (Tregs) and dysregulation in cytokine levels. The purpose of this article is to examine innate and adaptive immune cell phenotypes and functional characteristics that have not been previously examined in CFS/ME patients. Thirty patients with CFS/ME and 25 non-fatigued controls were recruited for this study. Whole blood samples were collected from all participants for the assessment of cell phenotypes, functional properties, receptors, adhesion molecules, antigens and intracellular proteins using flow cytometric protocols. The cells investigated included NK cells, dendritic cells, neutrophils, B cells, T cells, γδT cells and Tregs. Significant changes were observed in B-cell subsets, Tregs, CD4(+)CD73(+)CD39(+) T cells, cytotoxic activity, granzyme B, neutrophil antigens, TNF-α and IFN-γ in the CFS/ME patients in comparison with the non-fatigued controls. Alterations in B cells, Tregs, NK cells and neutrophils suggest significant impairments in immune regulation in CFS/ME and these may have similarities to a number of autoimmune disorders.

Fms-like tyrosine kinase 3 ligand-dependent dendritic cells in autoimmune inflammation

Dendritic cells (DCs) are specialized in capture, processing and presentation of antigens to T cells. Depending on the type of DC and its activation state, the interaction of DCs with naive T cells can lead to different types of immune response, or to T-cell tolerance. The existence of many specialized subtypes of DCs with particular functions has raised the need to distinguish DCs formed in steady-state from those produced during an inflammatory response. In patients with autoimmune disease and in experimental animal models of autoimmunity, DCs show abnormalities in both numbers and activation state, expressing immunogenic levels of co-stimulatory molecules and pro-inflammatory cytokines. Initial in vitro studies of cytokines in DC development revealed distinct and important roles for the receptor tyrosine kinases, granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF, also called CSF1) and fms-like tyrosine kinase 3 ligand (Flt3L) in the generation of DCs. Flt3L is critical for instructing DC generation throughout different organs and regulates DC development from Flt3(+) lymphoid and myeloid-committed progenitors to DCs in vivo. The aim of this review is to provide an overview of the role of Flt3L-dependent DCs in the immunopathogenesis of autoimmunity and chronic inflammation and its potential as therapeutic targets.

Systemic minor histocompatibility antigen expression in blood endothelial cells prevents T cell-mediated vascular immunopathology

Attenuation of T cell-mediated damage of blood endothelial cells (BECs) in transplanted organs is important to prevent transplant vasculopathy (TV) and chronic rejection. Here, we assessed the importance of minor histocompatibility antigen (mHA) distribution and different coinhibitory molecules for T cell-BEC interaction. A transgenic mHA was directed specifically to BECs using the Tie2 promoter and cellular interactions were assessed in graft-versus-host disease-like and heterotopic heart transplantation settings. We found that cognate CD4(+) T-cell help was critical for the activation of BEC-specific CD8(+) T cells. However, systemic mHA expression on BECs efficiently attenuated adoptively transferred, BEC-specific CD4(+) and CD8(+) T cells and hence prevented tissue damage, whereas restriction of mHA expression to heart BECs precipitated the development of TV. Importantly, the lack of the coinhibitory molecules programmed death-1 (PD-1) and B and T lymphocyte attenuator fostered the initial activation of BEC-specific CD4(+) T cells, but did not affect development of TV. In contrast, TV was significantly augmented in the absence of PD-1 on BEC-specific CD8(+) T cells. Taken together, these results indicate that antigen distribution in the vascular bed determines the impact of coinhibition and, as a consequence, critically impinges on T cell-mediated vascular immunopathology.

Development of a transgenic mouse model with immune tolerance for human coagulation factor VIIa

PURPOSE

Human factor VIIa (FVIIa) is commonly used as bypassing therapy to treat bleeding episodes in hemophilia patients with neutralizing antibodies to factors VIII (FVIII) or IX (FIX). There is a need for a suitable animal model to assess the immunogenicity of new FVIIa products during preclinical development. The aim of this study was the design of a novel transgenic mouse model with immune tolerance to human FVIIa.

METHODS

The model was generated by transgenic expression of human F7 cDNA. FVIIa-specific immune responses after treatment with human FVIIa were assessed by analyzing circulating antibodies, antibody producing plasma cells and CD4(+) T cells.

RESULTS

In contrast to wild-type mice, human FVII transgenic mice did not develop antibodies when treated with human FVIIa. The immune tolerance was specific and could be broken by application of human FVIIa together with a strong stimulus of the innate immune system. Break of tolerance was associated with increased numbers of pro-inflammatory FVIIa-specific CD4(+) T cells.

CONCLUSIONS

The new mouse model is suitable to study the influence of the innate immune system on maintenance and break of immune tolerance against FVIIa and could be used to assess the immunogenicity of new FVIIa products during pre-clinical development.

Dendritic cells: cellular mediators for immunological tolerance

In general, immunological tolerance is acquired upon treatment with non-specific immunosuppressive drugs. This indiscriminate immunosuppression of the patient often causes serious side-effects, such as opportunistic infectious diseases. Therefore, the need for antigen-specific modulation of pathogenic immune responses is of crucial importance in the treatment of inflammatory diseases. In this perspective, dendritic cells (DCs) can have an important immune-regulatory function, besides their notorious antigen-presenting capacity. DCs appear to be essential for both central and peripheral tolerance. In the thymus, DCs are involved in clonal deletion of autoreactive immature T cells by presenting self-antigens. Additionally, tolerance is achieved by their interactions with T cells in the periphery and subsequent induction of T cell anergy, T cell deletion, and induction of regulatory T cells (Treg). Various studies have described, modulation of DC characteristics with the purpose to induce antigen-specific tolerance in autoimmune diseases, graft-versus-host-disease (GVHD), and transplantations. Promising results in animal models have prompted researchers to initiate first-in-men clinical trials. The purpose of current review is to provide an overview of the role of DCs in the immunopathogenesis of autoimmunity, as well as recent concepts of dendritic cell-based therapeutic opportunities in autoimmune diseases.

Inhibition of islet immunoreactivity by adiponectin is attenuated in human type 1 diabetes

CONTEXT

Adiponectin is an adipocyte-derived cytokine with insulin-sensitizing and antiinflammatory properties. These dual actions have not previously been examined in the context of human disease.

OBJECTIVES

Our objective was to examine the adiponectin axis in type 1 diabetes (T1D). T1D is an autoimmune inflammatory disease resulting from pancreatic β-cell destruction, in which insulin resistance associates with progression to disease.

DESIGN, PATIENTS, AND INTERVENTIONS

We measured circulating adiponectin and adiponectin receptor expression on blood-immune cells from 108 matched healthy, T1D, and type 2 diabetic subjects. We tested adiponectin effect on T cell proliferation to islet antigens and antigen-presenting function of monocyte-derived dendritic cells (mDCs). Lastly, we assessed the effect of a 3-week lifestyle intervention program on immune cell adiponectin receptor expression in 18 healthy subjects.

RESULTS

Circulating concentrations of adiponectin were not affected by T1D. However, expression of adiponectin receptors on blood monocytes was markedly reduced and inversely associated with insulin resistance. Reduced adiponectin receptor expression resulted in increased T cell proliferation to islet-antigen presented by autologous mDCs. We demonstrated a critical role for adiponectin in down-regulating the costimulatory molecule CD86 on mDCs, and this function was impaired in T1D. We proceeded to show that lifestyle intervention increased adiponectin receptor but reduced CD86 expression on monocytes.

CONCLUSIONS

These data indicate that T cells are released from the antiinflammatory effects of adiponectin in T1D and suggest a mechanism linking insulin resistance and islet immunity. Furthermore, we suggest that interventions that reduce insulin resistance could modulate the inflammatory process in T1D.

Follicular dendritic cells emerge from ubiquitous perivascular precursors

The differentiation of follicular dendritic cells (FDC) is essential to the remarkable microanatomic plasticity of lymphoid follicles. Here we show that FDC arise from ubiquitous perivascular precursors (preFDC) expressing platelet-derived growth factor receptor β (PDGFRβ). PDGFRβ-Cre-driven reporter gene recombination resulted in FDC labeling, whereas conditional ablation of PDGFRβ(+)-derived cells abolished FDC, indicating that FDC originate from PDGFRβ(+) cells. Lymphotoxin-α-overexpressing prion protein (PrP)(+) kidneys developed PrP(+) FDC after transplantation into PrP(-) mice, confirming that preFDC exist outside lymphoid organs. Adipose tissue-derived PDGFRβ(+) stromal-vascular cells responded to FDC maturation factors and, when transplanted into lymphotoxin β receptor (LTβR)(-) kidney capsules, differentiated into Mfge8(+)CD21/35(+)FcγRIIβ(+)PrP(+) FDC capable of trapping immune complexes and recruiting B cells. Spleens of lymphocyte-deficient mice contained perivascular PDGFRβ(+) FDC precursors whose expansion required both lymphoid tissue inducer (LTi) cells and lymphotoxin. The ubiquity of preFDC and their strategic location at blood vessels may explain the de novo generation of organized lymphoid tissue at sites of lymphocytic inflammation.

Tertiary lymphoid organs in infection and autoimmunity

The lymph nodes (LNs) and spleen have an optimal structure that allows the interaction between T cells, B cells and antigen-presenting dendritic cells (DCs) on a matrix made up by stromal cells. Such a highly organized structure can also be formed in tertiary lymphoid organs (TLOs) at sites of infection or chronic immune stimulation. This review focuses on the molecular mechanisms of TLO formation and maintenance, the controversies surrounding the nature of the inducing events, and the functions of these structures in infection, transplantation and autoimmunity.

Do β-defensins and other antimicrobial peptides play a role in neuroimmune function and neurodegeneration?

It is widely accepted that the brain responds to mechanical trauma and development of most neurodegenerative diseases with an inflammatory sequelae that was once thought exclusive to systemic immunity. Mostly cationic peptides, such as the β-defensins, originally assigned an antimicrobial function are now recognized as mediators of both innate and adaptive immunity. Herein supporting evidence is presented for the hypothesis that neuropathological changes associated with chronic disease conditions of the CNS involve abnormal expression and regulatory function of specific antimicrobial peptides. It is also proposed that these alterations exacerbate proinflammatory conditions within the brain that ultimately potentiate the neurodegenerative process.

Regulation of Immune Responses by Spontaneous and T cell-mediated Dendritic Cell Death

In response to antigen stimulations, cells in the immune system undergo dynamic activation, differentiation, expansion and turnover. Programmed cell death is important for maintaining homeostasis of different cell types in the immune system. Dendritic cells (DCs) are a heterogeneous population of antigen presenting cells that capture, process and present antigens to stimulate lymphocytes. DCs have also emerged as major regulators of both innate and adaptive immune responses. Conventional myeloid DCs are relatively short-lived compared to lymphocytes in lymphoid organs. Mitochondrion-dependent apoptosis governed by Bcl-2 family members plays a major role in regulating spontaneous DC turnover. Killing of DCs by antigen-specific T cells also provides a negative feedback mechanism to restrict the duration and the scope of immune responses. Defects in cell death in DCs lead to DC accumulation, resulting in overactivation of lymphocytes and the development of autoimmunity in mice. Programmed cell death in DCs may play essential roles in the regulation of the duration and magnitude of immune responses, and in the protection against autoimmunity and uncontrolled inflammation.

Maturation profiles of peripheral blood dendritic cells in patients with endogenous uveitis

To determine whether or not maturation of dendritic cells (DCs) is associated with pathogenesis of endogenous uveitis, we analyzed expression of maturation markers, including CD80, CD86, and human leukocyte antigen (HLA)-DR, in peripheral blood (PB) DCs for comparison between healthy controls (HCs) and uveitis patients. A total of 21 patients and 16 HCs were included. Flow cytometric analysis was performed using PB DCs during the active phase of intraocular inflammation. CD86 and HLA-DR expression was higher in PB DCs from uveitis patients versus HCs, whereas that of CD80 was not significantly different. Levels of CD86 and HLA-DR expression tended to parallel those of inflammatory activity, and decreased after anti-inflammatory therapy. However, expression of CD86 and HLA-DR, even in remission, was not completely down-regulated to the low levels found in HCs. Our results indicate the maturation of DCs may play a role in the pathogenesis of endogenous uveitis. The relatively high expression of HLA-DR and co-stimulatory molecules even in the quiescence of inflammation suggests maturation of DCs may be associated with chronicity and recurrence of uveitis.

Deletion of cannabinoid receptors 1 and 2 exacerbates APC function to increase inflammation and cellular immunity during influenza infection

We and others have reported that simultaneous targeted deletion of CB(1) and CB(2) resulted in exacerbation of immune reactivity, suggesting a role of endocannabinoids in down-regulating immune function. In this study, we demonstrate that APC function is enhanced specifically in the absence of CB(1) and CB(2) signaling, resulting in an exacerbated immune response phenotype. After influenza infection, CB(1)(-/-)CB(2)(-/-) mice showed more pronounced pulmonary damage, increased inflammatory cell infiltrate, inflammation, and a greater cellular immune responses compared with WT mice, as evidenced by transcriptome analysis, more robust T cell activation, and effector cell cytokine production. After direct activation in vitro, there were no differences in the percentages of cytokine-producing CD4(+) T cells between CB(1)(-/-)CB(2)(-/-) and WT mice. However, untreated CB(1)(-/-)CB(2)(-/-) mice routinely had fewer naïve T cells compared with WT, suggesting dysregulation of APC immune homeostasis. Moreover, bmDCs and AM isolated from CB(1)(-/-)CB(2)(-/-) mice exhibited a more mature phenotype, with and without TLR stimulation, and bmDCs elicited T cells more robustly than WT mice. Collectively, these findings implicate a role for CB(1) and CB(2) on APCs in regulating immune responses and immune homeostasis.

TLR7/9 versus TLR3/MDA5 signaling during virus infections and diabetes

IFN-I are pleiotropic cytokines that impact innate and adaptive immune responses. In this article, we discuss TLR7/9 versus TLR3/MDA5 signaling in antiviral responses and diabetes. pDCs are thought to have a critical role in antiviral defense because of their ability to rapidly secrete large amounts of IFN-I through TLR7/9 signaling. A recent study demonstrates that although pDCs are a source of IFN-I in vivo, their overall contribution to viral containment is limited and time-dependent, such that additional cellular sources of IFN-I are required to fully control viral infections. dsRNA sensors, such as TLR3 and MDA5, provide another important trigger for antiviral IFN-I responses, which can be exploited to enhance immune responses to vaccines. In the absence of infection, IFN-I production by pDCs or from signaling through dsRNA sensors has been implicated in the pathogenesis of autoimmune diseases such as diabetes. However, recent data demonstrate that IFN-I production via TLR3 and MDA5 is critical to counter diabetes caused by a virus with preferential tropism for pancreatic β-cells. This highlights the complexity of the host antiviral response and how multiple cellular and molecular components balance protective versus pathological responses.

Current state of type 1 diabetes immunotherapy: incremental advances, huge leaps, or more of the same?

Thus far, none of the preclinically successful and promising immunomodulatory agents for type 1 diabetes mellitus (T1DM) has conferred stable, long-term insulin independence to diabetic patients. The majority of these immunomodulators are humanised antibodies that target immune cells or cytokines. These as well as fusion proteins and inhibitor proteins all share varying adverse event occurrence and severity. Other approaches have included intact putative autoantigens or autoantigen peptides. Considerable logistical outlays have been deployed to develop and to translate humanised antibodies targeting immune cells, cytokines, and cytokine receptors to the clinic. Very recent phase III trials with the leading agent, a humanised anti-CD3 antibody, call into question whether further development of these biologics represents a step forward or more of the same. Combination therapies of one or more of these humanised antibodies are also being considered, and they face identical, if not more serious, impediments and safety issues. This paper will highlight the preclinical successes and the excitement generated by phase II trials while offering alternative possibilities and new translational avenues that can be explored given the very recent disappointment in leading agents in more advanced clinical trials.