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

Emerging strategies for treating autoimmune disease with genetically modified dendritic cells

Gene editing of living cells has become a crucial tool in medical research, enabling scientists to address fundamental biological questions and develop novel strategies for disease treatment. This technology has particularly revolutionized adoptive transfer cell therapy products, leading to significant advancements in tumor treatment and offering promising outcomes in managing transplant rejection, autoimmune disorders, and inflammatory diseases. While recent clinical trials have demonstrated the safety of tolerogenic dendritic cell (TolDC) immunotherapy, concerns remain regarding its effectiveness. This review aims to discuss the application of gene editing techniques to enhance the tolerance function of dendritic cells (DCs), with a particular focus on preclinical strategies that are currently being investigated to optimize the tolerogenic phenotype and function of DCs. We explore potential approaches for in vitro generation of TolDCs and provide an overview of emerging strategies for modifying DCs. Additionally, we highlight the primary challenges hindering the clinical adoption of TolDC therapeutics and propose future research directions in this field.

Crosstalk Between Immunity System Cells and Pancreas. Transformation of Stem Cells Used in the 3D Bioprinting Process as a Personalized Treatment Method for Type 1 Diabetes

Interactions between the immune system and the pancreas are pivotal in understanding how and why β cells' damage causes problems with pancreas functioning. Pancreatic islets are crucial in maintaining glucose homeostasis in organs, tissue and cells. Autoimmune aggression towards pancreatic islets, mainly β cells, leads to type 1 diabetes-one of the most prevalent autoimmune disease in the world, being a worldwide risk to health of many people. In this review, we highlight the role of immune cells and its influence in the development of autoimmunity in Langerhans islets. Moreover, we discuss the impact of the immunological factors on future understanding possible recurrence of autoimmunity on 3D-bioprinted bionic pancreas.

Dichotomous roles of co-stimulatory molecules in diabetes mellitus

Numerous studies have established the importance of immune dysfunction in the development of diabetes mellitus, including typ1 and typ2 diabetes, and it is worth noting that T cell activation acts a key role in the pathogenesis of loss of β cell mass, adipose inflammation and insulin resistance. Regarding as an important checkpoint in the process of T cell activation, co-stimulatory molecules interaction between antigen present cells and T cells have been identified the critical role in the development of diabetes mellitus. Thus, blockage of co-stimulatory dyads interaction between antigen present cells and T cells was supposed to a potential of therapeutic strategies. However, studies also showed that inhibition or deletion of some co-stimulatory molecules do not always reduce the development of diabetes, and even exacerbate the disease activity. Here, in this context, we highlight the dichotomous role of co-stimulatory molecules interaction in the pathogenesis of diabetes.

miRNAs: novel regulators of autoimmunity-mediated pancreatic β-cell destruction in type 1 diabetes

MicroRNAs (miRNAs) are a series of conserved, short, non-coding RNAs that modulate gene expression in a posttranscriptional manner. miRNAs are involved in almost every physiological and pathological process. Type 1 diabetes (T1D) is an autoimmune disease that is the result of selective destruction of pancreatic β-cells driven by the immune system. miRNAs are also important participants in T1D pathogenesis. Herein, we review the most recent data on the potential involvement of miRNAs in T1D. Specifically, we focus on two aspects: the roles of miRNAs in maintaining immune homeostasis and regulating β-cell survival and/or functions in T1D. We also discuss circulating miRNAs as potent biomarkers for the diagnosis and prediction of T1D and investigate potential therapeutic approaches for this disease.

Rituximab in Minimal Change Disease: Mechanisms of Action and Hypotheses for Future Studies

Treatment with rituximab, a monoclonal antibody against the B-lymphocyte surface protein CD20, leads to the depletion of B cells. Recently, rituximab was reported to effectively prevent relapses of glucocorticoid-dependent or frequently relapsing minimal change disease (MCD). MCD is thought to be T-cell mediated; how rituximab controls MCD is not understood. In this review, we summarize key clinical studies demonstrating the efficacy of rituximab in idiopathic nephrotic syndrome, mainly MCD. We then discuss immunological features of this disease and potential mechanisms of action of rituximab in its treatment based on what is known about the therapeutic action of rituximab in other immune-mediated disorders. We believe that studies aimed at understanding the mechanisms of action of rituximab in MCD will provide a novel approach to resolve the elusive immune pathophysiology of MCD.

Regulatory T and B lymphocytes in a spontaneous autoimmune polyneuropathy

B7-2(-/-) non-obese diabetic (NOD) mice develop a spontaneous autoimmune polyneuropathy (SAP) that mimics the progressive form of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). In this study, we focused on the role of regulatory T cells (Tregs ) and regulatory B cells (Bregs ) in SAP. We found that deletion of B7-2 in female NOD mice led to a lower frequency and number of Tregs and Bregs in spleens and lymph nodes. Tregs but not Bregs suppressed antigen-stimulated splenocyte proliferation, whereas Bregs inhibited the T helper type 1 (Th1) cytokine response. Both Tregs and Bregs induced an increase in CD4(+) interleukin (IL)-10(+) cells, although less effectively in the absence of B7-2. Adoptive transfer studies revealed that Tregs , but not Bregs , suppressed SAP, while Bregs attenuated disease severity when given prior to symptom onset. B cell deficiency in B cell-deficient (muMT)/B7-2(-/-) NOD mice prevented the development of SAP, which would indicate that the pathogenic role of B cells predominates over its regulatory role in this model. We conclude that Bregs and Tregs control the immunopathogenesis and progression of SAP in a non-redundant fashion, and that therapies aimed at expansion of Bregs and Tregs may be an effective approach in autoimmune neuropathies.

Impaired dendritic cell function in a spontaneous autoimmune polyneuropathy

Spontaneous autoimmune polyneuropathy (SAP) in B7-2 knockout NOD mice mimics the progressive form of chronic inflammatory demyelinating polyradiculoneuropathy, and is mediated by myelin protein zero (P0)-reactive Th1 cells. In this study, we focused on the effect of B7-2 deletion on the function of dendritic cells (DCs) within the context of SAP. We found that development of SAP was associated with a preponderance or increase of CD11b(+) DCs in peripheral lymph nodes and sciatic nerves. B7-2 deletion led to altered immunophenotypic properties that differ between CD11b(+) DCs and CD8α(+) DCs. Both DC subsets from B7-2 knockout NOD mice exhibited impaired capacity to capture fluorophore-labeled myelin P0, but diminished Ag-presenting function was observed only in CD11b(+) DCs. Clinical assessment, electrophysiologic studies, and splenocyte proliferation studies revealed that absence of B7-2 on DCs was sufficient to cause impaired ability to induce tolerance to P0, which could be overcome by preconditioning with IL-10. Tolerance induction by Ag-pulsed wild-type NOD DCs was dependent on IL-10 and was associated with increased CD4(+) regulatory T cells, whereas tolerance induction by IL-10-conditioned B7-2-deficient DCs was associated with increased percentages of both regulatory T cells and B10 cells in the spleen. We conclude that B7-2 deletion has an impact on the distribution of DC subsets in lymphoid organs and alters the expression of costimulatory molecules, but functional consequences are not uniform across DC subsets. Defective tolerance induction in the absence of B7-2 can be restored by preconditioning of DCs with IL-10.

Late engagement of CD86 after influenza virus clearance promotes recovery in a FoxP3+ regulatory T cell dependent manner

Influenza A virus (IAV) infection in the respiratory tract triggers robust innate and adaptive immune responses, resulting in both virus clearance and lung inflammation and injury. After virus clearance, resolution of ongoing inflammation and tissue repair occur during a distinct recovery period. B7 family co-stimulatory molecules such as CD80 and CD86 have important roles in modulating T cell activity during the initiation and effector stages of the host response to IAV infection, but their potential role during recovery and resolution of inflammation is unknown. We found that antibody-mediated CD86 blockade in vivo after virus clearance led to a delay in recovery, characterized by increased numbers of lung neutrophils and inflammatory cytokines in airways and lung interstitium, but no change in conventional IAV-specific T cell responses. However, CD86 blockade led to decreased numbers of FoxP3+ regulatory T cells (Tregs), and adoptive transfer of Tregs into αCD86 treated mice rescued the effect of the blockade, supporting a role for Tregs in promoting recovery after virus clearance. Specific depletion of Tregs late after infection mimicked the CD86 blockade phenotype, confirming a role for Tregs during recovery after virus clearance. Furthermore, we identified neutrophils as a target of Treg suppression since neutrophil depletion in Treg-depleted mice reduced excess inflammatory cytokines in the airways. These results demonstrate that Tregs, in a CD86 dependent mechanism, contribute to the resolution of disease after IAV infection, in part by suppressing neutrophil-driven cytokine release into the airways.

In silico Analysis of TCR Vβ7 of Two Patients with Type 1 Diabetes Mellitus

OBJECTIVE

To compare the sequences and crystal structures of variable region of beta chain 7 (Vβ7) of T cell receptor (TCR) of two patients with type 1 diabetes mellitus (T1DM).

PATIENTS AND METHODS

The skewness of TCR Vβ7 of two T1DM patients were detected with real-time florescence quantitative polymerase chain reaction (FQ-PCR) and deoxyribonucleic acid (DNA) melting curve analysis technique followed by being sequenced, the crystal structures of them were simulated according to CPH models 2.0 Server, IMGT database, and RasMol 2 software.

RESULTS

The whole sequences of TCR Vβ7 of T1DM patient-1 were "CASRTAGQYEQYFGPGTR", that of patient-2 were "CASRTAGQYEQFFGPGTR"; the only difference between them lied on the 12(th) amino acid. The crystal structures of Vβ7 of the two patients simulated with backbone model were rather similar, while that with sphere model were obviously different.

CONCLUSION

Although the TCR Vβ7 of the T1DM patients share the similar gene sequences, their crystal structures simulated with sphere model are different, and the mechanism needs further study.

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.

Th17 cells in type 1 diabetes

T1D is an autoimmune disorder, which involves the CD4(+) as well as CD8(+) T-cell-mediated destruction of β cells. Recently, another population of T cells (Th17) is found to be involved in T1D pathology. This review will discuss the characteristics of Th17 cells and the mechanism of Th17-mediated T1D development. Th17 cell expansion is unstrained under T1D condition. Certain Treg cells are defective in T1D and lose the control of Th17 expansion. In addition, the altered function of APCs and a subset of monocytes which spontaneously secrete IL-1β and IL-6 in T1D determine the abnormal expansion of Th17 as well. The pathogenic Th17 cells can cause the imbalance between Teff and Treg cells. Conversion from Th17 to Th1 phenotype and Th17 stimulated CTL responses may play an accessory role in T1D as well. Due to the effects of Th17 on T1D, therapeutic strategies designed to inhibit these cells are applicable and the positive effects are obvious. Taken together, Th17 may exert essential effects on the development of T1D. Identification of the underlying mechanism may inspire new viewpoints for the therapy of this disease.

Immune mechanisms in spontaneously occurring CIDP in NOD mice

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an autoimmune disease affecting the peripheral nervous system (PNS) and is thought to involve both cellular and humoral immunity. Although its etiology remains to be fully elucidated, the use of animal models has provided some important information regarding its pathogenetic mechanisms. The development of a spontaneous autoimmune polyneuropathy (SAP) in B7-2 knockout non-obese diabetic (NOD) mice underscores the importance of co-stimulatory pathways such as B7-1/B7-2:CD28/CTLA-4 molecules in inflammatory neuropathies. These co-stimulatory molecules regulate the balance between pathogenic and regulatory T cells (Tregs). In SAP, pathogenic T cells are directed against myelin protein zero (P0), the most prominent PNS myelin protein that is a member of immunoglobulin gene superfamily.

Type 1 diabetes in BioBreeding rats is critically linked to an imbalance between Th17 and regulatory T cells and an altered TCR repertoire

Diabetes-prone BioBreeding (DP-BB) rats spontaneously develop type 1 diabetes mellitus (T1DM) on grounds of their MHC haplotype RT1(u) and a point mutation in the Gimap5 gene. In this study, we report that DP-BB rats exhibit an increasingly severe imbalance, in particular between Th17 and regulatory T (T(reg)) cells, within the first months of age. This can be assigned to an excess in effector T cells because neither the percentage nor the function of the T(reg) cells is compromised. Flow cytometric analysis of Vbeta segment usage and CDR3 spectratyping further suggest that the disturbed repertoire of peripheral T cells may also contribute to the development of T1DM in DP-BB rats. Importantly, expansion of T(reg) cells in vivo by means of a CD28 superagonistic Ab as well as adoptive transfer of T(reg) cells efficiently interferes with the development of T1DM in DP-BB rats, whereas treatment with conventional Th cells does not afford protection. Using a newly generated strain of enhanced GFP transgenic rats, we could further demonstrate that the transferred T(reg) cells persist in the recipient rats for several months and partially correct the imbalance between Th17 and T(reg) cells. Thus, our data support the hypothesis that unchecked effector T cell action and a disturbed T cell repertoire contribute to the development of T1DM in DP-BB rats, which may also have implications for a better understanding of the human disease.

Plasmacytoid dendritic cells in autoimmune diabetes - potential tools for immunotherapy

Type 1 diabetes (T1D) is an autoimmune disease in which a T-cell-mediated attack destroys the insulin-producing cells of the pancreatic islets. Despite insulin supplementation severe complications ask for novel treatments that aim at cure or delay of the onset of the disease. In spontaneous animal models for diabetes like the nonobese diabetic (NOD) mouse, distinct steps in the pathogenesis of the disease can be distinguished. In the past 10 years it became evident that DC and macrophages play an important role in all three phases of the pathogenesis of T1D. In phase 1, dendritic cells (DC) and macrophages accumulate at the islet edges. In phase 2, DC and macrophages are involved in the activation of autoreactive T cells that accumulate in the pancreas. In the third phase the islets are invaded by macrophages, DC and NK cells followed by the destruction of the beta-cells. Recent data suggest a role for a new member of the DC family: the plasmacytoid DC (pDC). pDC have been found to induce tolerance in experimental models of asthma. Several studies in humans and the NOD mouse support a similar role for pDC in diabetes. Mechanisms found to be involved in tolerance induction by pDC are inhibition of effector T cells, induction of regulatory T cells, production of cytokines and indoleamine 2,3-dioxygenase (IDO). The exact mechanism of tolerance induction by pDC in diabetes remains to be established but the intrinsic tolerogenic properties of pDC provide a promising, yet underestimated target for therapeutic intervention.

The cyclic AMP response element modulator {alpha} suppresses CD86 expression and APC function

The cAMP response element modulator (CREM)alpha is a widely expressed transcriptional repressor that is important for the termination of the T cell immune response and contributes to the abnormal T cell function in patients with systemic lupus erythematosus. We present evidence that APCs of Crem(-/-) mice express increased amounts of the costimulatory molecule CD86 and induce enhanced Ag-dependent and Ag-independent T cell proliferation. Similarly, human APCs in which CREMalpha was selectively suppressed expressed more CD86 on the surface membrane. CREMalpha was found to bind to the CD86 promoter and suppressed its activity. Transfer of APCs from Crem(-/-) mice into naive mice facilitated a significantly stronger contact dermatitis response compared with mice into which APCs from Crem(+/+) mice had been transferred. We conclude that CREMalpha is an important negative regulator of costimulation and APC-dependent T cell function both in vitro and in vivo.

Control of type 1 diabetes by CD4+Foxp3+ regulatory T cells: lessons from mouse models and implications for human disease

In recent years, there has been a revival of the concept of CD4(+) regulatory T (T(reg)) cells as being a central control point in various immune responses, including autoimmune responses and immunity to transplants, allergens, tumours and infectious microbes. The current literature suggests that T(reg) cells are diverse in their phenotype and mechanism(s) of action, and as such, may constitute a myriad of naturally occurring and induced T cell precursors with variable degrees of regulatory potential. In this review, we summarize research from various laboratories, including our own, showing that CD4(+)Foxp3(+) T(reg) cells are critical in the control of type 1 diabetes (T1D) in mouse models and humans. In this review, we also discuss cellular and molecular determinants that impact CD4(+)Foxp3(+) T(reg) cell development and function and consequential resistance to organ-specific autoimmune disease. Recent advances in the use of CD4(+)Foxp3(+) T(reg) cellular therapy to promote immunological tolerance in the absence of long-term generalized immunosuppression are also presented.

Targeting of myelin protein zero in a spontaneous autoimmune polyneuropathy

Elimination of the costimulatory molecule B7-2 prevents autoimmune diabetes in NOD mice, but leads to the development of a spontaneous autoimmune polyneuropathy (SAP), which resembles the human disease chronic inflammatory demyelinating polyneuropathy (CIDP). In this study, we examined the immunopathogenic mechanisms in this model, including identification of SAP Ags. We found that B7-2-deficient NOD mice exhibit changes in cytokine and chemokine gene expression in spleens over time. There was an increase in IL-17 and a decrease in IL-10 transcript levels at 4 mo (preclinical phase), whereas IFN-gamma expression peaked at 8 mo (clinical phase). There was also an increase in transcript levels of Th1 cytokines, CXCL10, and RANTES in sciatic nerves of mice that developed SAP. Splenocytes from SAP mice exhibited proliferative and Th1 cytokine responses to myelin P0 (180-199), but not to other P0 peptides or P2 (53-78). Adoptive transfer of P0-reactive T cells generated from SAP mice induced neuropathy in four of six NOD.SCID mice. Data from i.v. tolerance studies indicate that myelin P0 is one of the autoantigens targeted by T cells in SAP in this model. The expression of P0 by peri-islet Schwann cells provides a potential mechanism linking islet autoimmunity and inflammatory neuropathy.

Induction of innate immune response through TLR2 and dectin 1 prevents type 1 diabetes

Studies have suggested a correlation between the decline in infectious diseases and increase in the incidence of type 1 diabetes (T1D) in developed countries. Pathogens influence the disease outcome through innate immune receptors such as TLRs. Here we report the effect of ligation of TLR2 and dectin 1 on APCs and the influence of innate immune response induced through these receptors on T1D. Exposure of APCs of NOD mice to zymosan, a fungal cell wall component that interacts with TLR2 and dectin 1, resulted in the release of significant amounts of IL-10, TGF-beta1, IL-2, and TNF-alpha. Treatment of pre- and early hyperglycemic mice with zymosan resulted in suppression of insulitis, leading to a significant delay in hyperglycemia. T cells from zymosan-treated mice showed reduced ability to induce diabetes in NOD-Scid mice compared with control T cells. Zymosan treatment induced suppression of T1D was associated with an increase in the L-selectin(high) T cell frequencies and enhanced suppressor function of CD4(+)CD25(+) T regulatory cells. Further, activation by anti-CD3-Ab induced larger amounts of TGF-beta1 and/or IL-10 production by CD4(+)CD25(+) and CD4(+)CD25(-) T cells from zymosan-treated mice. These results show that innate immune response through TLR2 and dectin 1 results in suppressor cytokine production by APCs and promotes the regulatory function of T cells. Our study demonstrates the possible involvement of signaling through innate immune receptors such as TLR2 and dectin 1 in reduced T1D incidence under the conditions of low hygiene, and the potential of targeting them for treating T1D.

IL-21 limits peripheral lymphocyte numbers through T cell homeostatic mechanisms

Background

IL-21, a member of the common γ-chain utilizing family of cytokines, participates in immune and inflammatory processes. In addition, the cytokine has been linked to autoimmunity in humans and rodents.

Methodology/Principal Findings

To investigate the mechanism whereby IL-21 affects the immune system, we investigated its role in T cell homeostasis and autoimmunity in both non-autoimmune C57BL/6 and autoimmune NOD mice. Our data indicate that IL-21R knockout C57BL/6 and NOD mice show increased size of their lymphocyte population and decreased homeostatic proliferation. In addition, our experimental results demonstrate that IL-21 inhibits T cell survival. These data suggest that IL-21 acts to limit the size of the T cell pool. Furthermore, our data suggest IL-21 may contribute to the development of autoimmunity.

Conclusions/Significance

Taken together, our results suggest that IL-21 plays a global role in regulating T cell homeostasis, promoting the continuous adaptation of the T cell lymphoid space.

Preferential costimulation by CD80 results in IL-10-dependent TGF-beta1(+) -adaptive regulatory T cell generation

Costimulatory ligands CD80 and CD86 have different binding preferences and affinities to their receptors, CD28 and CTLA-4. Earlier, we demonstrated that CD80 binds to CTLA-4 with higher affinity and has a role in suppressing T cell response. The current study demonstrates that not only did blockade of CD86 upon Ag presentation by bone marrow-derived dendritic cells (DC) to OVA-specific T cells result in induction of hyporesponsive T cells but also that these T cells could suppress the proliferative response of effector T cells. These T cells showed TGF-beta1 on their surface and secreted TGF-beta1 and IL-10 upon restimulation. Although blockade of CTLA-4 and neutralization of IL-10 profoundly inhibited the induction of these TGF-beta1(+) T cells, their ability to suppress the effector T cell proliferation was abrogated by neutralization of TGF-beta1 alone. Induction of TGF-beta1(+) and IL-10(+) T cells was found to be independent of natural CD4(+)CD25(+) regulatory T cells, demonstrating that preferential ligation of CTLA-4 by CD80 induced IL-10 production by effector T cells, which in turn promoted the secretion of TGF-beta1. Treatment of prediabetic NOD mice with islet beta cell Ag-pulsed CD86(-/-) DCs, but not CD80(-/-) DCs, resulted in the induction of TGF-beta1- and IL-10-producing cells, significant suppression of insulitis, and delay of the onset of hyperglycemia. These observations demonstrate not only that CD80 preferentially binds to CTLA-4 but also that interaction during Ag presentation can result in IL-10-dependent TGF-beta1(+) regulatory T cell induction, reinstating the potential of approaches to preferentially engage CTLA-4 through CD80 during self-Ag presentation in suppressing autoimmunity.

B7-2 regulates survival, phenotype, and function of APCs

The absence of B7-2-mediated costimulation protects NOD mice from the development of diabetes. Although the effects of B7-2 on T cell priming are well known, its impact on the function of APCs is not fully elucidated. We tested APC function and survival in mice lacking B7-2. A significant reduction in the phagocytic ability was observed in both splenic and pancreatic lymph node-associated dendritic cells (DCs) in B7-2 knockout (KO) mice. DCs from B7-2KO mice exhibited enhanced susceptibility to death, which was reflected by their reduced total cell numbers. Phenotypic analysis of APCs in B7-2KO mice revealed a significantly decreased proportion of CD8alpha+CD205+ DCs. Interestingly, an enhanced proportion of B7-H1+ and B7-DC+ DCs were observed in B7-2KO mice. Lastly, we found that B7-2 deficiency significantly diminished the PKC-epsilon response in APCs upon CD28-Ig stimulation. In conclusion our data suggests that B7-2 promotes the generation of a mature APC repertoire and promotes APC function and survival.

B7-1 mediated costimulation regulates pancreatic autoimmunity

Costimulation by B7-1 and B7-2 molecules results in divergent biological effects. This is particularly striking in the NOD mouse, since the lack of B7-2 leads to complete protection from diabetes whereas the B7-1 deficiency causes exacerbation of disease. We tested the hypothesis that B7-1 costimulation suppresses pancreatic autoimmunity. We describe that the lack of B7-1 not only causes aberrant thymocyte maturation but also significantly enhances expansion, survival, and effector function of islet specific T cells in periphery. We also observed a significant reduction in the proportion of T-regulatory (T-regs) cells. Immunophenotypic analysis of T and APCs revealed a significantly lower frequency of T cells expressing the negative costimulatory receptor PD-1 in B7-1KO mice whereas the proportion of B7-H1 positive APCs was found to be significantly higher. Blocking studies in B7-1KO mice suggest that B7-H1 provides negative signals for anti islet CD4 and CD8 T-cell expansion but is differentially required for their priming. Our data demonstrate that deficiency of B7-1 mediated costimulation causes multitude of immunological defects, which involve reduction in T-regs and a concomitant enhancement of expansion, survival and effector potential of auto reactive T cells.

Immunomodulation of the Anti-Islet CD8 T Cell Response by B7-2

The absence of diabetes in NOD mice devoid of B7-2 signifies a critical role played by B7-2 in promoting autoimmunity. We asked whether the CD8 T cell compartment is impacted by the absence of B7-2. We found significantly lower expansion of anti-islet CD8 T cells in B7-2KO mice, although their survival and activation states remained unchanged in the pancreatic lymph nodes (PLNs). CD8 T cells from B7-2KO mice exhibited significantly diminished effector function compared to NOD mice. Adoptive transfer experiments using in vitro activated anti-islet CD8 T cells showed that B7-2 does not control the effector phase of the autoreactive CD8 T cell response. Our data indicate that B7-2 promotes pancreatic autoimmunity by controlling CD8 T cell expansion and effector function, but is dispensable for CD8 T cell activation, survival, and the effector phase of anti-islet CD8 T cell response.

Regulatory T-cell physiology and application to treat autoimmunity

Endowed with the ability to actively suppress an immune response, regulatory T cells (Tregs) hold the promise of halting ongoing pathogenic autoimmunity and restoring self-tolerance in patients suffering from autoimmune diseases. Through many in vitro and in vivo studies, we have learned that Tregs can function in the lymph nodes as well as in the peripheral tissues. In vivo, Tregs act through dendritic cells to limit autoreactive T-cell activation, thus preventing their differentiation and acquisition of effector functions. By limiting the supply of activated pathogenic cells, Tregs prevent or slow down the progression of autoimmune diseases. However, this protective mechanism appears insufficient in autoimmune individuals, likely because of a shortage of Tregs cells and/or the development and accumulation of Treg-resistant pathogenic T cells over the long disease course. Thus, restoration of self-tolerance in these patients will likely require purging of pathogenic T cells along with infusion of Tregs with increased ability to control ongoing tissue injury. In this review, we highlight advances in dissecting Treg function in vivo in autoimmune settings and summarize multiple studies that have overcome the limitations of the low abundance of Tregs and their hypoproliferative phenotype to develop Treg-based therapies.

TLR2 and TLR4 differentially regulate B7-1 resulting in distinct cytokine responses to the mycoplasma superantigen MAM as well as to disease induced by Mycoplasma arthritidis

Mycoplasma arthritidis mitogen (MAM) is a superantigen secreted by M. arthritidis, an agent of murine arthritis and toxicity. We previously demonstrated that C3H mouse sub-strains differing in expression of Toll-like receptor 4 (TLR4), differed in immune reactivity to MAM due to differential engagement of TLR2 and TLR4. Here we examine the role of B7 co-stimulatory molecules in immune outcome and disease manifestations resulting from these different MAM/TLR2 and MAM/TLR4 interactions. Injections of MAM into C3H/HeJ mice upregulated expression of B7-1 but not B7-2 on peritoneal adherent cells, whereas B7-1 expression was lower on cells from C3H/HeSnJ mice. Anti-B7-1 antibody but not anti-B7-2, injected in vivo, changed the type 1 cytokines in MAM-injected C3H/HeJ mice to a type 2 cytokines and, conversely, the type 2 response in C3H/HeSnJ mice injected with anti-B7-1 shifted to a type 1 pattern. Whereas anti-B7-2 exerted no effect on disease in either mouse strain, anti-B7-1 significantly delayed the lethal toxicity of M. arthritidis in C3H/HeJ mice but enhanced arthritis in C3H/HeSnJ mice. Thus, TLR-mediated regulation of B7-1 results in diverse cytokine profiles in C3H sub-strains, and that the interaction of MAM with different TLR(s) may differentially affect cytokine responses and ultimately, M. arthritidis disease.