Treatment with anti-CD86 costimulatory molecule prevents the autoimmune lesions in murine Sjögren's syndrome (SS) through up-regulated Th2 response

The role of epithelial cells in the immunopathogenesis of Sjögren's syndrome

Sjögren's syndrome is a systemic autoimmune disease characterized by dysfunction of the affected exocrine glands. Lymphocytic infiltration within the inflamed glands and aberrant B-cell hyperactivation are the two salient pathologic features in Sjögren's syndrome. Increasing evidence indicates that salivary gland epithelial cells act as a key regulator in the pathogenesis of Sjögren's syndrome, as revealed by the dysregulated innate immune signaling pathways in salivary gland epithelium and increased expression of various proinflammatory molecules as well as their interaction with immune cells. In addition, salivary gland epithelial cells can regulate adaptive immune responses as nonprofessional antigen-presenting cells and promote the activation and differentiation of infiltrated immune cells. Moreover, the local inflammatory milieu can modulate the survival of salivary gland epithelial cells, leading to enhanced apoptosis and pyroptosis with the release of intracellular autoantigens, which further contributes to SG autoimmune inflammation and tissue destruction in Sjögren's syndrome. Herein, we reviewed recent advances in elucidating the role of salivary gland epithelial cells in the pathogenesis of Sjögren's syndrome, which may provide rationales for potential therapeutic targeting of salivary gland epithelial cells to alleviate salivary gland dysfunction alongside treatments with immunosuppressive reagents in Sjögren's syndrome.

Advances in Pathogenesis of Sjögren's Syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease of unknown etiology that mainly involves exocrine glands. Patients present with dry mouth and eyes, fever, arthralgia, and other systemic symptoms. In severe cases, the quality of life of patients is affected. At present, there is no cure for SS, and the treatment options are extremely limited. In recent years, studies of patients and animal models have identified abnormalities of immune cell function and cytokines to be involved in SS. A systematic review of the literature may clarify the etiology and pathogenesis of SS, as well as provide a theoretical basis for the development of new drugs for the treatment of SS.

Pathology of salivary gland dysfunction and restoration of function

In this review, the author shows that simultaneous multiple disorders caused by reactivation of Epstein-Barr virus can lead to salivary gland disorders as part of Sjogren's syndrome (SS). Therefore, clinicians must differentiate SS from other diseases when diagnosing and treating salivary gland disorders. In particular, the author explains how microbial infection in SS overcomes immunological tolerance, leading to pathological changes, and how cytokine overexpression and endocrine disrupters contribute to glandular tissue injury. Also, the author suggests that involvement of reactive oxygen species is a common pathogenesis of salivary gland disorders and SS, so regulation of oxidative stress is an effective treatment for both. The results of clinical studies on restoring salivary gland function and regenerating salivary glands with tissue stem cells may provide clues on elucidating the cause of SS.

Modulating the wayward T cell: New horizons with immune checkpoint inhibitor treatments in autoimmunity, transplant, and cancer

The T-cell response is regulated by the balance between costimulatory and coinhibitory signals. Immune checkpoints are essential for efficient T-cell activation, but also for maintaining self-tolerance and protecting tissues from damage caused by the immune system, and for providing protective immunity. Modulating immune checkpoints can serve diametric goals, such that blocking a coinhibitory molecule can unleash anti-cancer immunity whereas stimulating the same molecule can reduce an over-reaction in autoimmune disease. The purpose of this review is to examine the regulation of T-cell costimulation and coinhibition, which is central to the processes underpinning autoimmunity, transplant rejection and immune evasion in cancer. We will focus on the immunomodulation agents that regulate these unwanted over- and under-reactions. The use of such agents has led to control of symptoms and slowing of progression in patients with rheumatoid arthritis, reduced rejection rates in transplant patients, and prolonged survival in patients with cancer. The management of immune checkpoint inhibitor treatment in certain challenging patient populations, including patients with pre-existing autoimmune conditions or transplant patients who develop cancer, as well as the management of immune-related adverse events in patients receiving antitumor therapy, is examined. Finally, the future of immune checkpoint inhibitors, including examples of emerging targets that are currently in development, as well as recent insights gained using new molecular techniques, is discussed. T-cell costimulation and coinhibition play vital roles in these diverse therapeutic areas. Targeting immune checkpoints continues to be a powerful avenue for the development of agents suitable for treating autoimmune diseases and cancers and for improving transplant outcomes. Enhanced collaboration between therapy area specialists to share learnings across disciplines will improve our understanding of the opposing effects of treatments for autoimmune disease/transplant rejection versus cancer on immune checkpoints, which has the potential to lead to improved patient outcomes.

Recent Advances in Mouse Models of Sjögren's Syndrome

Sjögren's syndrome (SS) is a complex rheumatoid disease that mainly affects exocrine glands, resulting in xerostomia (dry mouth) and xerophthalmia (dry eye). SS is characterized by autoantibodies, infiltration into exocrine glands, and ectopic expression of MHC II molecules on glandular epithelial cells. In contrast to the well-characterized clinical and immunological features, the etiology and pathogenesis of SS remain largely unknown. Animal models are powerful research tools for elucidating the pathogenesis of human diseases. To date, many mouse models of SS, including induced models, in which disease is induced in mice, and genetic models, in which mice spontaneously develop SS-like disease, have been established. These mouse models have provided new insight into the pathogenesis of SS. In this review, we aim to provide a comprehensive overview of recent advances in the field of experimental SS.

Sjögren's syndrome: Old and new therapeutic targets

Sjögren's syndrome (SS) is a prototype autoimmune disease characterized by oral and ocular mucosal dryness following chronic inflammation of salivary and lachrymal glands, respectively. Profound B cell hyperactivity along with systemic manifestations including fatigue, musculoskeletal complaints, features related to hepatic, pulmonary, renal and nervous system involvement, as well as lymphoma development can be also present. Despite that activation of both innate and adaptive immune pathways has been long well documented in SS pathogenesis, systemic immunosuppression in SS, in contrast to other autoimmune diseases, has been largely inefficacious. Biological agents previously implemented in successful therapeutic outcomes in rheumatoid arthritis (RA), such as anti-TNF agents, anakinra, tocilizumab and rituximab failed to reach primary outcomes in randomized double-blind controlled trials in the context of SS. Abatacept and belimumab, already licensed for the treatment of RA and lupus respectively, as well combination regimens of both rituximab and belimumab hold some promise in alleviation of SS-specific complaints, but data from large controlled trials are awaited. Recent advances in dissecting the molecular pathways underlying SS pathogenesis led to an expanding number of novel biological compounds directed towards type I interferon system, antigen presentation, costimulatory pathways, B and T cell activation, as well as germinal center formation. While targeting of cathepsin-S (Petesicatib), inducible costimulator of T cells ligand (prezalumab), and lymphotoxin beta receptor (baminercept) failed to fulfil the primary outcome measures, preliminary results from two randomized placebo controlled trials on CD40 blockade (Iscalimab) and B-cell activating factor receptor (Ianalumab) inhibition resulted in significant reduction of SS disease activity, with a favorable so far safety profile. Results from administration of other kinase inhibitors, a transmembrane activator and calcium-modulator and cytophilin ligand interactor TACI fusion protein (RC18), as well as low dose recombinant interleukin-2 to expand T-regulatory cells are currently awaited.

Mechanisms and New Strategies for Primary Sjögren's Syndrome

Primary Sjögren's syndrome (SS) is a common chronic autoimmune disease characterized by lymphocytic infiltration of exocrine glands, mainly salivary and lacrimal, resulting in oral and ocular dryness, although virtually any organ system can be affected. SS-related systemic manifestations are classified as either related to the presence of periepithelial infiltrates in exocrine and parenchymal organs or resulting from immunocomplex deposition due to B cell hyperactivity with increased risk for B cell lymphoma development. Activation of both innate and adaptive immune pathways contributes to disease pathogenesis, with prominent interferon (IFN) signatures identified in both peripheral blood and affected salivary gland tissues. Recently, LINE-1 genomic repeat elements have been proposed as potential triggers of type I IFN pathway activation in SS through activation of Toll-like receptor-dependent and -independent pathways. In view of the increasingly appreciated variability of SS, elucidation of distinct operating pathways in relation to diverse clinical phenotypes and selection of the optimal therapeutic intervention remain major challenges. Inhibition of cathepsin S molecules, blockade of costimulation through administration of abatacept and inhibitors of B7-related molecules and CD40, blockade of B cell function and B cell survival factors, and disruption of the formation of ectopic germinal centers are considered the main therapeutic targets. Well-controlled multicenter clinical trials are ongoing and data are awaited.

Mouse Models of Primary Sjogren's Syndrome

Sjogren's syndrome (SjS) is a chronic autoimmune disorder characterized by immune cell infiltration and progressive injury to the salivary and lacrimal glands. As a consequence, patients with SjS develop xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes). SjS is the third most common rheumatic autoimmune disorder, affecting 4 million Americans with over 90% of patients being female. Current diagnostic criteria for SjS frequently utilize histological examinations of minor salivary glands for immune cell foci, serology for autoantibodies, and dry eye evaluation by corneal or conjunctival staining. SjS can be classified as primary or secondary SjS, depending on whether it occurs alone or in association with other systemic rheumatic conditions, respectively. Clinical manifestations typically become apparent when the disease is relatively advanced in SjS patients, which poses a challenge for early diagnosis and treatment of SjS. Therefore, SjS mouse models, because of their close resemblance to the human SjS, have been extremely valuable to identify early disease markers and to investigate underlying biological and immunological dysregulations. However, it is important to bear in mind that no single mouse model has duplicated all aspects of SjS pathogenesis and clinical features, mainly due to the multifactorial etiology of SjS that includes numerous susceptibility genes and environmental factors. As such, various mouse models have been developed in the field to try to recapitulate SjS. In this review, we focus on recent mouse models of primary SjS xerostomia and describe them under three categories of spontaneous, genetically engineered, and experimentally induced models. In addition, we discuss future perspectives highlighting pros and cons of utilizing mouse models and current demands for improved models.

Dysregulated co-stimulatory molecule expression in a Sjögren's syndrome mouse model with potential implications by microRNA-146a

Sjögren's syndrome (SjS) is an autoimmune condition that primarily affects salivary and lacrimal glands, causing loss of secretion. We have previously shown that microRNA-146a (miR-146a) is over-expressed in the salivary glands and peripheral blood mononuclear cells (PBMC) of SjS-prone mice (C57BL/6.NOD-Aec1Aec2, B6DC) and in PBMC of SjS patients. The purpose of this research was to identify a target molecule of miR-146a and identify subpopulations of cells affected by altered miR-146a in the salivary glands of SjS-prone mice. In silico analyses identified costimulatory molecule CD80 as a potential target of miR-146a. Luciferase assay of the human CD80 3'untranslated region demonstrated miR-146a directly inhibited CD80 protein expression as indicated by reduced luciferase reporter expression and an examination of B6DC salivary glands revealed a reduction in CD80 protein. More interestingly, the specific reduction in CD80 protein was detected from the salivary gland epithelial cell population and in interstitial dendritic cells in the glands as well. The reduction in CD80 protein levels in salivary gland epithelial cells were negatively associated with elevated miR-146a expression. Therefore, this study provides the first indication that salivary gland epithelial cells may be critically involved in SjS progression by altering CD86:CD80 protein ratio in response to miR-146a upregulation.

Immune checkpoint receptors in regulating immune reactivity in rheumatic disease

Immune checkpoint regulators are critical modulators of the immune system, allowing the initiation of a productive immune response and preventing the onset of autoimmunity. Co-inhibitory and co-stimulatory immune checkpoint receptors are required for full T-cell activation and effector functions such as the production of cytokines. In autoimmune rheumatic diseases, impaired tolerance leads to the development of diseases such as rheumatoid arthritis, systemic lupus erythematosus, and Sjogren’s syndrome. Targeting the pathways of the inhibitory immune checkpoint molecules CD152 (cytotoxic T lymphocyte antigen-4) and CD279 (programmed death-1) in cancer shows robust anti-tumor responses and tumor regression. This observation suggests that, in autoimmune diseases, the converse strategy of engaging these molecules may alleviate inflammation owing to the success of abatacept (CD152-Ig) in rheumatoid arthritis patients. We review the preclinical and clinical developments in targeting immune checkpoint regulators in rheumatic disease.

Affinity and cross-reactivity engineering of CTLA4-Ig to modulate T cell costimulation

CTLA4-Ig is an Fc fusion protein containing the extracellular domain of CTLA-4, a receptor known to deliver a negative signal to T cells. CTLA4-Ig modulates T cell costimulatory signals by blocking the CD80 and CD86 ligands from binding to CD28, which delivers a positive T cell costimulatory signal. To engineer CTLA4-Ig variants with altered binding affinity to CD80 and CD86, we employed a high-throughput protein engineering method to map the ligand binding surface of CTLA-4. The resulting mutagenesis map identified positions critical for the recognition of each ligand on the three CDR-like loops of CTLA-4, consistent with the published site-directed mutagenesis and x-ray crystal structures of the CTLA-4/CD80 and CTLA-4/CD86 complexes. A number of single amino acid substitutions were identified that equally affected the binding affinity of CTLA4-Ig for both ligands as well as those that differentially affected binding. All of the high-affinity variants showed improved off-rates, with the best one being a 17.5-fold improved off-rate over parental CTLA4-Ig binding to CD86. Allostimulation of human CD4(+) T cells showed that improvement of CD80 and CD86 binding activity augmented inhibition of naive and primed T cell activation. In general, increased affinity for CD86 resulted in more potent inhibition of T cell response than did increased affinity for CD80. Optimization of the affinity balance to CD80 and CD86 to particular disease settings may lead to development of a CTLA4-Ig molecule with improved efficacy and safety profiles.

Expression of CCR5 and its ligands CCL3, -4, and -5 in the tear film and ocular surface of patients with dry eye disease

PURPOSE

To evaluate the expression of CCR5 and its ligands CCL3, CCL4, and CCL5 in the tear film and ocular surface and their correlation with disease severity in patients with dry eye disease.

MATERIALS AND METHODS

The concentrations of CCL3, CCL4, and CCL5 were measured using enzyme-linked immunosorbent assay in tear samples obtained from forty-three patients with dry eye (17 SS and 26 non-SS patients) and 20 control subjects. The correlation between chemokine levels and tear film and ocular surface parameters was analyzed. Expression of the chemokines and their receptor in the conjunctiva was evaluated using immunohistochemistry. Flow cytometry was performed to detect CCR4+CD4+, CCR5+CD4+, and CCR6+CD4+ cells in the conjunctiva.

RESULTS

The concentrations of CCL3, CCL4, and CCL5 were 25.3 ± 24.2, 4.65 ± 3.21, and 93.12 ± 26.31 pg/mL in control subjects, 92.33 ± 13.23, 263.13 ± 116.13, and 253.64 ± 46.29 pg/mL in patients with non-SS, and 215.56 ± 36.1, 697.85 ± 185.65, and 456.12 ± 92.82 pg/mL in patients with SS. The concentrations showed a significant increase in tears of SS patients compared with those of non-SS patients and control subjects (p < 0.05). CCL5 levels showed significant correlation with tear film break-up time, basal tear secretion, tear clearance rate, keratoepitheliopathy score, and goblet cell density (p < 0.01). Staining for the chemokines and their receptor increased in dry eye patients, especially in those with SS patients. Flow cytometry demonstrated increased numbers of CCR5+CD4+, and CCR6+CD4+ cells in dry eye patients in contrast to CCR4+CD4+ cells.

CONCLUSIONS

Expression of CCR5 and its ligands CCL3, CCL4, and CCL5 increase in the tear film and ocular surface of patients with dry eye syndrome, especially in those with SS. CCL5 levels correlate significantly with various tear film and ocular surface parameters.

T cell targeted immunotherapy for autoimmune disease

Much emphasis has been placed on the so-called "biologics" in the treatment of immune disorders within the last few years. Here we discuss the expanding horizon of potential strategies for immunotherapies targeting T lymphocytes as key effectors and regulators of autoimmunity. We review emerging reagents in a variety of animal models and human disorders that may offer new therapeutic options in current or modified iterations.

B7 costimulation is critical for host control of chronic Mycobacterium tuberculosis infection

Although much is understood regarding the role of B7/CD28 family of costimulatory molecules in regulating host resistance in the context of several pathogens, analogous information with Mycobacterium tuberculosis is lacking. To address the requirements of B7-mediated costimulation in host resistance against tuberculosis, mice deficient in both B7.1 and B7.2 (B7DKO) were aerosol infected with M. tuberculosis Erdman and disease progression was monitored. We report herein that B7DKO mice are initially able to contain the bacterial load in the lung, but exhibit enhanced susceptibility during chronic infection. Despite the early control of bacterial replication, B7DKO mice essentially start off with compromised Th1 immunity and slower granulomatous response in the lung, characterized by markedly reduced lymphocytic infiltration. As the infection progresses from acute phase to the chronic phase, the nascent granulomas in the B7DKO lungs never fully achieve the architecture of granulomas developing in wild-type mice. Instead, lesions spread progressively to involve much of the lung in the B7DKO mice, ultimately leading to necrosis. Thus, early control of M. tuberculosis growth in the lung can occur in the absence of B7 costimulation and is less dependent on Th1 immunity and formation of a granulomatous structure. However, B7 costimulation is critical for long-term containment of infection within lung granulomas. These findings suggest that the use of costimulation-based immunomodulators may have significant repercussions on the induction of host protective immunity against tuberculosis.

Regulating the regulators: costimulatory signals control the homeostasis and function of regulatory T cells

SUMMARY

Costimulation is a concept that goes back to the early 1980s when Lafferty and others hypothesized that cell surface and soluble molecules must exist that are essential for initiating immune responses subsequent to antigen exposure. The explosion in this field of research ensued as over a dozen molecules have been identified to function as second signals following T-cell receptor engagement. By 1994, it seemed clear that the most prominent costimulatory pathway CD28 and functionally related costimulatory molecules, such as CD154, were the major drivers of a positive immune response. Then the immunology world turned upside down. CD28 knockout mice, which were, in most cases, immunodeficient, led to increased autoimmunity when bred into the non-obese diabetic background. Another CD28 family member, cytotoxic T-lymphocyte-associated protein 4, which was presumed to be a costimulatory molecule on activated T cells, turned out to be critical in downregulating immunity. These results, coupled with the vast suppressor cell literature which had been largely rebuked, suggested that the immune system was not poised for response but controlled in such a way that regulation was dominant. Over the last decade, we have learned that these costimulatory molecules play a key role in the now classical CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) that provide critical control of unwanted autoimmune responses. In this review, we discuss the connections between costimulation and Tregs that have changed the costimulation paradigm.

Effective treatment with oral administration of rebamipide in a mouse model of Sjögren's syndrome

OBJECTIVE

To determine whether oral administration of rebamipide, a mucosal protective agent, is effective in the treatment of Sjögren's syndrome (SS) in the NFS/sld mouse model of the disease.

METHODS

NFS/sld mice were given daily oral doses of rebamipide (0.3 mg/kg of body weight or 3 mg/kg) or vehicle alone starting from the age of 4 weeks to the age of 8 weeks. The volume of saliva and tears was monitored during and after treatment. After the final dose, histologic features of the tissues, TUNEL+ apoptotic duct cells in affected glands, T cell and cytokine function, and levels of immunoglobulin isotypes and serum autoantibodies were examined.

RESULTS

The 3-mg/kg dose of rebamipide prevented the development of autoimmune lesions. The average volume of saliva in rebamipide-treated mice was significantly higher than that in control mice. We found decreased TUNEL+ apoptotic duct cells in the salivary and lacrimal glands of rebamipide-treated mice as compared with control mice. Rebamipide treatment suppressed the activation of CD4+ T cells and Th1 cytokines (interleukin-2, interferon-gamma) associated with impaired NF-kappaB activity. Production of serum autoantibodies, IgM, and IgG1 was clearly inhibited.

CONCLUSION

Our findings demonstrate the efficacy of oral administration of rebamipide in the treatment of SS. Rebamipide represents a new therapeutic strategy for the treatment of patients with sicca symptoms caused by SS, as well as for patients with other diseases.

T lymphocytes in Sjögren's syndrome: contributors to and regulators of pathophysiology

Sjögren's syndrome is a chronic autoimmune disorder characterized by lymphocytic infiltration and malfunction of the exocrine glands, resulting in dry mouth and eyes. This multigenic and multifunctional disease can present as primary Sjögren's syndrome or secondary to an underlying connective tissue disease. Immune activation subsequent to activation or apoptosis of glandular epithelial cells in genetically predisposed individuals may expose autoantigens, which engage self-perpetuating T cell dependent autoimmune sequelae. The cellular and molecular context of this immune response may drive proinflammatory (Th1 and Th17) and restrain inhibitory (Treg) pathways. Inability to suppress the immune response results in persistent tissue damage and compromised function of salivary and lacrimal glands. Defining the contributions of participating T cells may unravel strategies for therapeutic intervention.

The presence of GM-CSF and IL-4 interferes with effect of TGF-beta1 on antigen presenting cells in patients with multiple sclerosis and in rats with experimental autoimmune encephalomyelitis

The possibility to generate and expand tolerogenic dendritic cells (DC) with TGF-beta1 in vitro opens new therapeutic perspectives for the treatment of autoimmune diseases. In the present study, GM-CSF+IL-4 induced the differentiation of DC from adherent peripheral blood mononuclear cells, which had a higher expression of HLA-DR, CD86 and CD1a and the capacity to stimulate T cells. TGF-beta1 alone slightly promoted the generation of antigen presenting cells (APC) with higher expression of CD14, but did not differentiate them into E-cadherin+Langerhans cell (LC)-like DC. TGF-beta1-driven APC exhibited the morphology, phenotypes and functions of tolerogenic immature DC, and had lower capacity to stimulate T cells. In vivo experiment demonstrates that TGF-beta1-treated APC exhibited the therapeutic potential in Lewis rats with experimental autoimmune encephalomyelitis (EAE), followed by increase of IL-10 production in lymph nodes and decrease of inflammatory cells in spinal cords. Most importantly, GM-CSF/IL-4 used in DC preparation abolished the effect of TGF-beta1 to induce tolerogenic APC in vitro and in vivo. The results reveal that the usage of GM-CSF for the generation of tolerogenic DC should not be copied from DC preparation for anti-tumor therapy.

Usefulness of liver infiltrating CD86-positive mononuclear cells for diagnosis of autoimmune hepatitis

AIM: Although the pathogenic mechanism underlying autoimmune hepatitis (AIH) remains unclear, the immune system is thought to be critical for the progression of the disease. Cellular immune responses may be linked to the hepatocellular damage in AIH. Recently, much attention has been focused on the critical functions of costimulatory molecules expressed on mononuclear cells in the generation of effective T cell-mediated immune responses. Analysis of costimulatory molecule expressed on mononuclear cells from the patients with AIH may give us insight into the pathogenic mechanism of hepatocellular damage in AIH.

METHODS: Peripheral blood mononuclear cells (PBMC) were taken from the patients with AIH (34 cases) and healthy controls (25 cases). Liver infiltrating mononuclear cells (LIMCs) were taken from the patients with AIH (18 cases), the patient with chronic hepatitis C (CH-C) (13 cases) and the patients with fatty liver (2 cases). Using flow cytometry, the cells were analyzed for the expression of costimulatory molecules, such as CD80, CD86, and CD152 (CTLA-4). The results were compared with clinical data such as the level of gammaglobulin, histological grade, presence or absence of corticosteroids administration and the response to corticosteroids.

RESULTS: The levels of CD80+, CD86+ and CD152+ PBMC were significantly reduced in the patients with AIH as compared with healthy controls. By contrast, those cells were significantly higher in LIMC than in PBMC of the patients with AIH. Especially, the level of CD86+ LIMC showed a marked increase irrespective of the degree of disease activity in the patients with AIH, although CD86+ cells were rarely present in PBMC. The levels of CD86+ cells were present in significantly higher frequency in patients with AIH than in the patients with CH-C. Furthermore, the patients with AIH with high levels of CD86+ LIMC showed good responses to corticosteroids, whereas 2 cases of AIH with low levels of CD86+ LIMC did not respond well.

CONCLUSION: These results suggest that LIMC over-expressing costimulatory molecules such as CD80 and CD86 appears to play a role in the pathogenesis of AIH. Especially, CD86 molecule expressed on the LIMC may be useful for the diagnosis of AIH and for the prediction of the therapeutic effects of corticosteroids on AIH.

B7-1 and B7-2 selectively recruit CTLA-4 and CD28 to the immunological synapse

The reported affinity differences between CD28 and CTLA-4 binding to B7-1 and B7-2 may serve to selectively regulate CD28 and CTLA-4 function by differentially recruiting and/or stabilizing these molecules at the immunological synapse. Here we show that ligand binding is important for the accumulation of both CD28 and CTLA-4 at the synapse. While CD28 is recruited to the synapse in the absence of B7-1 and B7-2 binding, it is not effectively stabilized there, as its localization can be disrupted by CTLA-4. In the case of CTLA-4, ligand binding is critical for its concentration at the synapse. We also demonstrate that the affinity and avidity differences in ligand binding translate into selective recruitment of CD28 or CTLA-4 to the immunological synapse--B7-1 is the major ligand mediating CTLA-4 localization, while B7-2 is the main ligand for CD28 concentration at the synapse.

Effective treatment of a mouse model of Sjögren's syndrome with eyedrop administration of anti-CD4 monoclonal antibody

OBJECTIVE

To determine whether eyedrop administration of an anti-CD4 monoclonal antibody (mAb) is effective in the treatment of Sjögren's syndrome (SS) using a mouse model of the disease.

METHODS

The anti-CD4 mAb was administered daily into the eyes of mice with SS from ages 4 to 8 weeks or ages 10 to 12 weeks. During treatment, tear volume was monitored and after final treatment, histologic features of the lacrimal and salivary glands, the phenotypes and function of T cells, and serum titers of anti-alpha-fodrin antibody were examined.

RESULTS

Eyedrop administration of anti-CD4 mAb before the onset of SS prevented the autoimmune pathology seen in the lacrimal glands but not that in the salivary glands. Furthermore, eyedrop administration of anti-CD4 mAb after the development of SS inhibited mononuclear cell infiltration and the destruction of parenchyma only in the lacrimal glands. Eyedrop administration of anti-CD4 mAb suppressed the local activation of CD4+ T cells rather than deleting CD4+ T cells, which reduced the expansion of pathologic CD4+ T cells against alpha-fodrin.

CONCLUSION

These results demonstrate the remarkable efficacy of anti-CD4 mAb eyedrops in the treatment of SS eye symptoms, which illustrates a new antibody-based therapeutic strategy for patients with eye problems caused by SS as well as other diseases.

B7-2 (CD86) Controls the Priming of Autoreactive CD4 T Cell Response against Pancreatic Islets

The B7-1/2-CD28 system provides the critical signal for the generation of an efficient T cell response. We investigated the role played by B7-2 in influencing pathogenic autoimmunity from islet-reactive CD4 T cells in B7-2 knockout (KO) NOD mice which are protected from type 1 diabetes. B7-2 deficiency caused a profound diminishment in the generation of spontaneously activated CD4 T cells and islet-specific CD4 T cell expansion. B7-2 does not impact the effector phase of the autoimmune response as adoptive transfer of islet Ag-specific BDC2.5 splenocytes stimulated in vitro could easily induce disease in B7-2KO mice. CD4 T cells showed some hallmarks of hyporesponsiveness because TCR/CD28-mediated stimulation led to defective activation and failure to induce disease in NODscid recipients. Furthermore, CD4 T cells exhibited enhanced death in the absence of B7-2. Interestingly, we found that B7-2 is required to achieve normal levels of CD4+CD25+CD62L+ T regulatory cells because a significant reduction of these T regulatory cells was observed in the thymus but not in the peripheral compartments of B7-2KO mice. In addition, our adoptive transfer experiments did not reveal either pathogenic or regulatory potential associated with the B7-2KO splenocytes. Finally, we found that the lack of B7-2 did not induce a compensatory increase in the B7-1 signal on APC in the PLN compartment. Taken together these results clearly indicate that B7-2 plays a critical role in priming islet-reactive CD4 T cells, suggesting a simplified, two-cell model for the impact of this costimulatory molecule in autoimmunity against islets.

Clinical significance of costimulatory molecules CD80/CD86 expression in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common form of human glomerulonephritis. Tubulointerstitial inflammation with infiltration of mononuclear cells plays an important role in the progression of IgAN. Activation of T cells requires costimulatory signals through binding of CD28 receptor with cognate ligands (CD80/CD86) located on antigen-presenting cells (APC). To assess the clinical significance of this regulatory pathway participation in the pathogenesis of IgAN, a comprehensive immunohistologic evaluation was conducted on renal tissue of IgAN in different phases of progressive injury.

METHODS

Thirty-three cases of IgAN and ten cases of non-IgA mesangial proliferative glomerulonephritis (PGN) with minor tissue damage as controls were investigated. Monoclonal antibodies were used to assess the expression of CD80, CD86, CD68, CD14, CD45RO, human leukocyte antigen-DR (HLA-DR), and intercellular adhesion molecule-1 (ICAM-1) in renal tissues. Clinical and expression data were compared at the time of renal biopsy.

RESULTS

CD80+ and CD86+ cells were observed more in IgAN patients with progressive renal injury than in mild cases and controls. CD80 was limited to tubular epithelial cells and was complemented by HLA-DR expression. CD86 was expressed in the glomerulus, periglomerular area, and peritubular interstitium. Activated T cells (CD45RO+), monocytes (CD14+), macrophages (CD68+), and CD86 showed similar distributions. Positive correlations were found between CD86+ cells and CD45RO, CD14, and CD68 positive cells and between CD80+ tubuli and peritubular interstitial CD45RO+ cells. The number of interstitial CD86 positive cells and the percentage of CD80+ tubuli were correlated with renal function. Most CD86+ cells were monocyte/macrophages.

CONCLUSION

This study suggested that CD80 and CD86 activate T cells in IgAN, CD80/CD86 expressions correlated with renal function at the time of renal biopsy, and monocyte/macrophages and tubular epithelial cells act as APC.

Presence of B7-2+ dendritic cells and expression of Th1 cytokines in the early development of sialodacryoadenitis in the IqI/Jic mouse model of primary Sjörgren's syndrome

Subpopulations of infiltrating lymphocytes, professional antigen-presenting cells (APCs), and Th1/Th2 cytokines that could initiate an autoimmune sialodacryoadenitis were studied in the IQI/Jic mouse model of primary Sjögren's syndrome. Although lymphocytic infiltrations were first seen in submandibular glands (SMGs) of females and in lacrimal glands (LGs) of males at 8 weeks of age, clusters of MHC class II+, CD11c+, B7-2+ dendritic cells (DCs) were already localized in these tissues at 4 weeks. At 8 weeks, the infiltrating lymphocytes consisted of almost equal numbers of B cells and CD4+ T cells. In the inflammatory foci, MHC class II+, CD11c+, B7-2+ DCs formed network-like structures. Duct cells in the lesions showed immunoreactivities for MHC class II and ALCAM (a costimulatory adhesion molecule). IL-12 and IFN-gamma transcripts were detected by RT-PCR in SMGs of females and in LGs of males at 8-12 weeks. These results suggest that the clustered DCs might play an important role in the initiation of the adenitis, and further suggest that the DCs and epithelial cells may participate in the activation of CD4+ T cells. It is also likely that Th1 cytokines mediate the functional interactions between the APCs and CD4+ T cells in the early lesions.

Costimulatory molecules CD80 and CD86 in human crescentic glomerulonephritis

BACKGROUND

CD80 and CD86, cell-surface molecules found only on antigen-presenting cells (APCs), are required for activation of CD4-postitve (CD4+) T cells by interaction with CD28/cytotoxic T-lymphocyte-associated antigen 4 on T cells. The roles of these molecules in human glomerulonephritis (GN) presently are unknown.

METHODS

Twelve cases of crescentic GN, thought to be a T helper cell-directed delayed-type hypersensitivity-like injury, and 10 controls with non-immunoglobulin A proliferative GN were used. Expression of CD80, CD86, CD4, CD14, CD68, HLA-DR, and intercellular adhesion molecule-1 was investigated in renal tissues using monoclonal antibodies and compared with clinical data at the time of renal biopsy.

RESULTS

CD80+ and CD86+ cells were observed significantly more in crescentic GN than in controls. CD86 was expressed in the glomerulus and interstitium, especially in the crescent, and adhesion to Bowman's capsule and periglomerular areas corresponding to these changes. Tubular epithelial cells showed no CD86 expression, but they expressed CD80, and some of them expressed HLA-DR. CD4, CD14, CD68, and CD86 showed similar distribution patterns. Positive correlations were found between CD86+ cells and CD4+, CD14+, and CD68+ cells. The number of interstitial CD86+ cells correlated with deterioration of renal function. Most CD86+ cells were monocyte/macrophages.

CONCLUSION

This study suggests that the costimulatory molecules CD80 and CD86 have different expressions in human crescentic GN, and CD86 is concerned with crescent formation and CD4+ T-cell accumulations. The majority of APCs are macrophages, and tubular cells also can act as APCs.

B7-1 and B7-2 co-stimulatory molecules are required for mercury-induced autoimmunity

B7-1 (CD80) and B7-2 (CD86) molecules on antigen presenting cells play important roles in providing co-stimulatory signals required for activation and expansion of autoreactive T cells. Moreover, some reports have suggested that these molecules may have distinct functions in the differentiation of Th1 and Th2 cells. Mercury-induced autoimmunity in H-2s mice is characterized by lymphoproliferation of T and B cells, serum increases in IgG1 and IgE and production of antinucleolar antibodies (ANoA). The mechanisms responsible for the various manifestations of this syndrome have yet to be elucidated. To examine the contributions of B7 co-stimulatory molecules to this model, susceptible mice were treated with antibodies to B7-1, B7-2, or both during the development of mercury-induced autoimmunity. The combination of anti-B7-1 and anti-B7-2 antibodies prevented Hg-induced disease in H-2s mice. Additionally, single anti-B7-1 antibody treatment was sufficient to prevent Hg-induced ANoA production, but not IgG1 and IgE hypergammaglobulinaemia. Further, single antibody treatment with anti-B7-2 resulted in a partial reduction of ANoA titres but had no significant effect on total serum IgG1 and IgE levels. Taken together, these results indicate that B7-1 and B7-2 molecules are critical for the development of Hg-induced autoimmunity and suggest that the different manifestations of the syndrome are regulated by independent mechanisms.

CD80(B7.1) and CD86(B7.2) do not have distinct roles in setting the Th1/Th2 balance in autoimmunity in rats

Some data suggest that the interaction between CD28 and CD80 (B7.1) stimulates Th1-responses and that CD28 and CD86 (B7.2) stimulates Th2-responses, however this is controversial. We addressed this issue by using mercuric chloride (HgCl2)-induced autoimmunity in Brown Norway (BN) rats as a highly polarized Th2 model and experimental autoimmune encephalomyelitis (EAE) in Lewis rats as a highly polarized Th1 model. Monoclonal antibodies (MoAbs) to CD80 and CD86, given singly, had little effect in either model, however when given together they almost completely suppressed the HgCl2-induced autoimmunity: the peak immunoglobulin (Ig)E concentration was 3.25 microg/ml in treated animals versus 2770 microg/ml in controls (P < 0.0001); caecal vasculitis was suppressed with a median vasculitis score of 0 in treated animals versus 6 in controls (P < 0.0001); and new germinal centre formation was significantly suppressed. A combination of the antibodies also markedly reduced the severity of clinical EAE; from a median aggregate clinical score of 9 to 3 (P = 0.02) and delayed the onset from a median of 12.5 days to 16 days after immunization (P = 0.006). We have demonstrated profound suppression of both Th1 and Th2-driven autoimmunity in rats by a combination of anti-CD80 and CD86, but have been unable to demonstrate any clear differential effects.

Complexities of CD28/B7: CTLA-4 costimulatory pathways in autoimmunity and transplantation

Recent advances in the understanding of T cell activation have led to new therapeutic approaches in the treatment of immunological disorders. One attractive target of intervention has been the blockade of T cell costimulatory pathways, which result in more selective effects on only those T cells that have encountered specific antigen. In fact, in some instances, costimulatory pathway antagonists can induce antigen-specific tolerance that prevents the progression of autoimmune diseases and organ graft rejection. In this review, we summarize the current understanding of these complex costimulatory pathways including the individual roles of the CD28, CTLA-4, B7-1 (CD80), and B7-2 (CD86) molecules. We present evidence that suggests that multiple mechanisms contribute to CD28/B7-mediated T cell costimulation in disease settings that include expansion of activated pathogenic T cells, differentiation of Th1/Th2 cells, and the migration of T cells into target tissues. Additionally, the negative regulatory role of CTLA-4 in autoimmune diseases and graft rejection supports a dynamic but complex process of immune regulation that is prominent in the control of self-reactivity. This is most apparent in regulation of the CD4(+)CD25(+)CTLA-4(+) immunoregulatory T cells that control multiple autoimmune diseases. The implications of these complexities and the potential for use of these therapies in clinical immune intervention are discussed.

Pathogenesis of rheumatoid arthritis. The role of T cells and other beasts

The evidence coming from the different experimental approaches reviewed in this article strongly supports the hypothesis that RA is T-cell driven at all stages of the disease. Although the effector phases responsible for the events that lead to joint destruction involve several different cell types, cytokines, and other mediators, T cells still direct operations behind the scenes. Direct experimental proof of this proposition in patients is still lacking, but the development of nondepleting modulating CD4 monoclonal antibodies may provide new tools to test this hypothesis. In this respect, it is encouraging that using one such reagent, we have recently shown that not only did the activity of the disease improve but, more importantly, the inflammatory indices and production of non-T-cell cytokines were reduced. This is not to dissimilar from the results of experiments described in animals, where by blocking synovial T cells, the production of IL-1 beta and TNF alpha could be decreased by more than 90%. From this perspective, it may be predicted that by modulating T cells in the joint, it is possible to achieve our ultimate goal of permanently switching off the disease.

Role of CD30+ T cells in rheumatoid arthritis: a counter-regulatory paradigm for Th1-driven diseases

CD30 has been proposed to identify Th0/2-type clones. However, the in vivo relevance of this finding is still a matter of debate, as high serum levels of soluble CD30 have been found in both Th1- and Th2- dominated disorders. Among these, rheumatoid arthritis represents a condition where the Th1 predominance is combined with the presence of CD30(+) T-cell activity, particularly in specific stages of the disease. This article discusses the hypothesis that CD30(+) T cells might play a counter-regulatory role at sites of inflammation in Th1-mediated conditions, such as rheumatoid arthritis.

Sjögren syndrome

Sjögren syndrome is a chronic systemic disease characterized by polyglandular tissue destruction leading to keratoconjunctivitis sicca (KCS) and xerostomia. Patients with primary Sjögren syndrome show evidence of KCS and xerostomia, whereas patients with secondary Sjögren syndrome suffer from KCS, xerostomia, and an autoimmune disease, most commonly rheumatoid arthritis. Certain factors cause autoimmune dysregulation leading to destruction of the acinar cells and ductal epithelia with subsequent dry eyes and dry mouth. Activated lymphocytes in patients with autoimmune diseases appear to have selective homing into the lacrimal and salivary glands leading to tissue damage. Understanding the factors involved in the immune dysregulation may improve our diagnostic and therapeutic approaches in Sjögren syndrome. Current therapeutic measures include means to increase secretion, relieve symptoms, and repair damage of the ocular surface.

Update in Sjögren syndrome

Sjögren syndrome (SS), the second most common autoimmune rheumatic disease, refers to keratoconjunctivitis sicca and xerostomia resulting from immune lymphocytes that infiltrate the lacrimal and salivary glands. However, differential diagnosis remains confusing due to the high prevalence of vague symptoms of dryness, fatigue, and myalgias in the general population. The problems of diagnosis are further compounded by the finding of "positive" antinuclear antibodies in a high percent of the general population. Unless minor salivary gland biopsies are read by experienced observers, nonspecific changes of sialadenitis are frequently confused with the focal lymphocytic infiltrates that are characteristic of SS. The distinction between fibromyalgia patients with low titer antinuclear antibodies and primary SS remains difficult. Even in patients fulfilling strict criteria for SS, the genomic search for critical genes has proven difficult due to the multigenic pattern of inheritance and strong role of currently undefined environmental factors. No single environmental factor has been detected in the majority of SS patients. SS-like syndrome has been detected in certain patients with HTLV-1 and hepatitis C infection, providing clues to pathogenesis. Even in SS patients with marked sicca symptoms, minor salivary gland biopsy shows that almost 50% of glandular cells are still detected on biopsy. These results imply the importance of immune factors such as cytokines and autoantibodies in decreasing neuro-secretory circuits and induction of glandular dysfunction. Of potential importance, an antibody against muscarinic M3 receptor that can decrease secretory function when injected into rodents is frequently found in the sera of SS patients. Newly developed topical and oral therapies can ease the oral and ocular dryness. Orally administered agonists of the muscarinic M3 receptor (pilocarpine and cevimeline) have recently been approved by the US Food and Drug Administration to increase salivary secretion. Topical ocular use of low-dose corticosteroids or cyclosporin may decrease conjunctival surface inflammation. In a Phase II double-blind study, orally administered interferon alpha (150 U) led to improved saliva flow and symptoms. In pregnant patients with evidence of fetal distress, oral dexamethasone is preferred because this agent crosses the placenta effectively. In animal models, antagonists of tumor necrosis factor and inhibitors of de novo pyrimidine synthesis appear promising.