Naturally occurring immunoglobulin M (nIgM) autoantibodies prevent autoimmune diabetes and mitigate inflammation after transplantation

A human IgM enriched immunoglobulin preparation, Pentaglobin, reverses autoimmune diabetes without immune suppression in NOD mice

The immune system of healthy individuals is capable of regulating autoimmunity through multiple mechanisms. In Type 1 Diabetes (T1D) we recently discovered natural IgM, although present at normal levels, is unable to perform its normal immunoregulatory function. Treating diabetic mice with IgM from healthy donors led to reversal of disease without immune depletion. To investigate the therapeutic potential of a human preparation of IgM, we administered an IgM-enriched preparation of immunoglobulin called Pentaglobin. Administration of Pentaglobin therapy reversed disease in diabetic NOD mice and boosted CD4 + Foxp3 + Tregs. Importantly, the impact of Pentaglobin on the immune system was limited to inhibiting beta cell destruction but was not immune depleting nor did it inhibit the immunization response to an irrelevant antigen. These findings indicate that inhibition of deleterious autoimmunity in T1D is possible while leaving protective immunity fully intact.

Cyclic swelling enabled, electrically conductive 3D porous structures for microfluidic urinalysis devices

Urinalysis is a simple and non-invasive approach for the diagnosis and monitoring of organ health and also is often used as a facile technique in assessment of substance abuse. However, quantitative urinalysis is predominantly limited to clinical laboratories. Here, we present an electrical sensing based, reusable, cellular microfluidic device that offers a fast urinalysis through quantitative reading of the electrical signals. The spatial soft porous scaffolds decorated with electrically conductive multiwalled carbon nanotubes that are capable of physically interacting with biomarkers in urine are developed through a cyclic swelling/absorption process of soft materials and are utilized to manufacture the cellular microfluidic device. The sensing capability, sensitivity and reusability (via sunlight exposure) of the device to monitor red blood cells, Escherichia coli, and albumin are systemically demonstrated by programming mechanical deformation of porous scaffolds. Ex vivo experiments in disease mouse models confirm the diagnosis robustness of the device in comparable results with existing biochemical tests. The full integration of electrically conductive nanomaterials into soft scaffolds provides a foundation for devising bioelectronic devices with mechanically programmable microfluidic features in a low-cost manner, with broad applications for rapid disease diagnoses through body fluid.

Adaptive tolerance: Protection through self-recognition

The random nature of immunoglobulin gene segment rearrangement inevitably leads to the generation of self-reactive B cells. Avoidance of destructive autoimmune reactions is necessary in order to maintain physiological homeostasis. However, current central and peripheral tolerance concepts fail to explain the massive number of autoantibody-borne autoimmune diseases. Moreover, recent studies have shown that in physiological mouse models autoreactive B cells were neither clonally deleted nor kept in an anergic state, but were instead able to mount autoantibody responses. We propose that activation of autoreactive B cells is induced by polyvalent autoantigen complexes that can occur under physiological conditions. Repeated encounter of autoantigen complexes leads to the production of affinity-matured autoreactive IgM that protects its respective self-targets from degradation. We refer to this novel mechanism as adaptive tolerance. This article discusses the discovery of adaptive tolerance and the unexpected role of high affinity IgM autoantibodies.

Healthy Donor Polyclonal IgMs Diminish B-Lymphocyte Autoreactivity, Enhance Regulatory T-Cell Generation, and Reverse Type 1 Diabetes in NOD Mice

Autoimmune diseases such as type 1 diabetes (T1D) arise from unrestrained activation of effector lymphocytes that destroy target tissues. Many efforts have been made to eliminate these effector lymphocytes, but none has produced a long-term cure. An alternative to depletion therapy is to enhance endogenous immune regulation. Among these endogenous alternatives, naturally occurring Igs have been applied for inflammatory disorders but have lacked potency in antigen-specific autoimmunity. We hypothesized that naturally occurring polyclonal IgMs, which represent the majority of circulating, noninduced antibodies but are present only in low levels in therapeutic Ig preparations, possess the most potent capacity to restore immune homeostasis. Treatment of diabetes-prone NOD mice with purified IgM isolated from Swiss Webster (SW) mice (nIgM_SW) reversed new-onset diabetes, eliminated autoreactive B lymphocytes, and enhanced regulatory T-cell (Treg) numbers both centrally and peripherally. Conversely, IgM from prediabetic NOD mice could not restore this endogenous regulation, which represents an unrecognized component of T1D pathogenesis. Of note, IgM derived from healthy human donors was similarly able to expand human CD4 Tregs in humanized mice and produced permanent diabetes protection in treated NOD mice. Overall, these studies demonstrate that a potent, endogenous regulatory mechanism, nIgM, is a promising option for reversing autoimmune T1D in humans.

Evidence for the Role of the Cecal Microbiome in Maintenance of Immune Regulation and Homeostasis

OBJECTIVE (S)

Our objective was to investigate alterations in the cecal microbial composition during the development of type 1 diabetes (T1D) with or without IgM therapy, and correlate these alterations with the corresponding immune profile.

METHODS

(1) Female nonobese diabetic (NOD) mice treated with IgM or saline (n = 20/group) were divided into 5-week-old nondiabetic; 9 to 12-week-old prehyperglycemic stage-1; ≥13-week-old prehyperglycemic stage-2; and diabetic groups. 16S rRNA libraries were prepared from bacterial DNA and deep-sequenced. (2) New-onset diabetic mice were treated with IgM (200 μg on Days 1, 3, and 5) and their blood glucose monitored for 2 months.

RESULTS

Significant dysbiosis was observed in the cecal microbiome with the progression of T1D development. The alteration in microbiome composition was characterized by an increase in the bacteroidetes:firmicutes ratio. In contrast, IgM conserved normal bacteroidetes:firmicutes ratio and this effect was long-lasting. Furthermore, oral gavage using cecal content from IgM-treated mice significantly diminished the incidence of diabetes compared with controls, indicating that IgM specifically affected mucosa-associated microbes, and that the affect was causal and not an epiphenomenon. Also, regulatory immune cell populations (myeloid-derived suppressor cells and regulatory T cells) were expanded and insulin autoantibody production diminished in the IgM-treated mice. In addition, IgM therapy reversed hyperglycemia in 70% of new-onset diabetic mice (n = 10) and the mice remained normoglycemic for the entire post-treatment observation period.

CONCLUSIONS

The cecal microbiome appears to be important in maintaining immune homeostasis and normal immune responses.

An engineered macroencapsulation membrane releasing FTY720 to precondition pancreatic islet transplantation

Macroencapsulation is a powerful approach to increase the efficiency of extrahepatic pancreatic islet transplant. FTY720, a small molecule that activates signaling through sphingosine-1-phosphate receptors, is immunomodulatory and pro-angiogenic upon sustained delivery from biomaterials. While FTY720 (fingolimod, Gilenya) has been explored for organ transplantation, in the present work the effect of locally released FTY720 from novel nanofiber-based macroencapsulation membranes is explored for islet transplantation. We screened islet viability during culture with FTY720 and various biodegradable polymers. Islet viability is significantly reduced by the addition of high doses (≥500 ng/mL) of soluble FTY720. Among the polymers screened, islets have the highest viability when cultured with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Therefore, PHBV was blended with polycaprolactone (PCL) for mechanical stability and electrospun into nanofibers. Islets had no detectable function ex vivo following 5 days or 12 h of subcutaneous implantation within our engineered device. Subsequently, we explored a preconditioning scheme in which islets are transplanted 2 weeks after FTY720-loaded nanofibers are implanted. This allows FTY720 to orchestrate a local regenerative milieu while preventing premature transplantation into avascular sites that contain high concentrations of FTY720. These results provide a foundation and motivation for further investigation into the use of FTY720 in preconditioning sites for efficacious islet transplantation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 555-568, 2018.

Natural IgM and TLR Agonists Switch Murine Splenic Pan-B to "Regulatory" Cells That Suppress Ischemia-Induced Innate Inflammation via Regulating NKT-1 Cells

Natural IgM anti-leukocyte autoantibodies (IgM-ALAs) inhibit inflammation by several mechanisms. Here, we show that pan-B cells and bone marrow-derived dendritic cells (BMDCs) are switched to regulatory cells when pretreated ex vivo with IgM. B cells are also switched to regulatory cells when pretreated ex vivo with CpG but not with LPS. Pre-emptive infusion of such ex vivo induced regulatory cells protects C57BL/6 mice from ischemia-induced acute kidney injury (AKI) via regulation of in vivo NKT-1 cells, which normally amplify the innate inflammatory response to DAMPS released after reperfusion of the ischemic kidney. Such ex vivo induced regulatory pan-B cells and BMDC express low CD1d and inhibit inflammation by regulating in vivo NKT-1 in the context of low-lipid antigen presentation and by a mechanism that requires costimulatory molecules, CD1d, PDL1/PD1, and IL10. Second, LPS and CpG have opposite effects on induction of regulatory activity in BMDC and B cells. LPS enhances regulatory activity of IgM-pretreated BMDC but negates the IgM-induced regulatory activity in B cells, while CpG, with or without IgM pretreatment, induces regulatory activity in B cells but not in BMDC. Differences in the response of pan-B and dendritic cells to LPS and CpG, especially in the presence of IgM-ALA, may have relevance during infections and inflammatory disorders where there is an increased IgM-ALA and release of TLRs 4 and 9 ligands. Ex vivo induced regulatory pan-B cells could have therapeutic relevance as these easily available cells can be pre-emptively infused to prevent AKI that can occur during open heart surgery or in transplant recipients receiving deceased donor organs.

Role of Natural IgM Autoantibodies (IgM-NAA) and IgM Anti-Leukocyte Antibodies (IgM-ALA) in Regulating Inflammation

Natural IgM autoantibodies (IgM-NAA) are rapidly produced to inhibit pathogens and abrogate inflammation mediated by invading microorganisms and host neoantigens. IgM-NAA achieve this difficult task by being polyreactive with low binding affinity but with high avidity, characteristics that allow these antibodies to bind antigenic determinants shared by pathogens and neoantigens. Hence the same clones of natural IgM can bind and mask host neoantigens as well as inhibit microorganisms. In addition, IgM-NAA regulate the inflammatory response via mechanisms involving binding of IgM to apoptotic cells to enhance their removal and binding of IgM to live leukocytes to regulate their function. Secondly, we review how natural IgM prevents autoimmune disorders arising from pathogenic IgG autoantibodies as well as by autoreactive B and T cells that have escaped tolerance mechanisms. Thirdly, using IgM knockout mice, we show that regulatory B and T cells require IgM to effectively regulate inflammation mediated by innate, adaptive and autoimmune mechanisms. It is therefore not surprising why the host positively selects such autoreactive B1 cells that generate protective IgM-NAA, which are also evolutionarily conserved. Fourthly, we show that IgM anti-leukocyte autoantibodies (IgM-ALA) levels and their repertoire can vary in normal humans and disease states and this variation may partly explain the observed differences in the inflammatory response after infection, ischemic injury or after a transplant. Finally we also show how protective IgM-NAA can be rendered pathogenic under non-physiological conditions. IgM-NAA have therapeutic potential. Polyclonal IgM infusions can be used to abrogate ongoing inflammation. Additionally, inflammation arising after ischemic kidney injury, e.g., during high-risk elective cardiac surgery or after allograft transplantation, can be prevented by pre-emptively infusing polyclonal IgM, or DC pretreated ex vivo with IgM, or by increasing in vivo IgM with a vaccine approach. Cell therapy with IgM pretreated cells, is appealing as less IgM will be required.

Toll-Like Receptor (TLR)4 and MyD88 are Essential for Atheroprotection by Peritoneal B1a B Cells

BACKGROUND

We previously identified peritoneal B1a cells that secrete natural IgM as a key atheroprotective B cell subset. However, the molecules that activate atheroprotective B1a cells are unknown. Here, we investigated whether Toll-like receptors (TLRs) TLR2, TLR4, and TLR9 expressed by B1a cells are required for IgM-mediated atheroprotection.

METHODS AND RESULTS

We adoptively transferred B1a cells from wild-type mice or from mice deficient in TLR2, TLR4, TLR9, or myeloid differentiation primary response 88 (MyD88) into ApoE-/- mice depleted of peritoneal B1a cells by splenectomy and fed a high-fat diet for 8 weeks. Elevations in plasma total, anti-oxLDL (oxidized low-density lipoprotein), anti-leukocyte, anti-CD3, anti-CD8, and anti-CD4 IgMs in atherosclerotic mice required B1a cells expressing TLR4 and MyD88, indicating a critical role for TLR4-MyD88 signaling for IgM secretion. Suppression of atherosclerosis was also critically dependent on B1a cells expressing TLR4-MyD88. Atherosclerosis suppression was associated not only with reductions in lesion apoptotic cells, necrotic cores, and oxLDL, but also with reduced lesion CD4+ and CD8+ T cells. Transforming growth factor beta 1 (TGF-β1) expression, including macrophages expressing TGF-β1, was increased, consistent with increased IgM-mediated phagocytosis of apoptotic cells by macrophages. Reductions in lesion inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin (IL) 1β, and IL-18 were consistent with augmented TGF-β1 expression.

CONCLUSIONS

TLR4-MyD88 expression on B1a cells is critical for their IgM-dependent atheroprotection that not only reduced lesion apoptotic cells and necrotic cores, but also decreased CD4 and CD8 T-cell infiltrates and augmented TGF-β1 expression accompanied by reduced lesion inflammatory cytokines TNF-α, IL-1β, and IL-18.

Role of Natural Autoantibodies and Natural IgM Anti-Leucocyte Autoantibodies in Health and Disease

We review how polyreactive natural IgM autoantibodies (IgM-NAA) protect the host from invading micro-organisms and host neo-antigens that are constantly being produced by oxidation mechanisms and cell apoptosis. Second, we discuss how IgM-NAA and IgM anti-leukocyte antibodies (IgM-ALA) inhibits autoimmune inflammation by anti-idiotypic mechanisms, enhancing removal of apoptotic cells, masking neo-antigens, and regulating the function of dendritic cells (DC) and effector cells. Third, we review how natural IgM prevents autoimmune disorders arising from pathogenic IgG autoantibodies, triggered by genetic mechanisms (e.g., SLE) or micro-organisms, as well as by autoreactive B and T cells that have escaped tolerance mechanisms. Studies in IgM knockout mice have clearly demonstrated that regulatory B and T cells require IgM to effectively regulate inflammation mediated by innate, adaptive, and autoimmune mechanisms. It is, therefore, not surprising why the host positively selects such autoreactive B1 cells that generate IgM-NAA, which are also evolutionarily conserved. Fourth, we show that IgM-ALA levels and their repertoire can vary in normal humans and disease states and this variation may partly explain the observed differences in the inflammatory response after infection, ischemic injury, or after a transplant. We also show how protective IgM-NAA can be rendered pathogenic under non-physiological conditions. We also review IgG-NAA that are more abundant than IgM-NAA in plasma. However, we need to understand if the (Fab)(2) region of IgG-NAA has physiological relevance in non-disease states, as in plasma, their functional activity is blocked by IgM-NAA having anti-idiotypic activity. Some IgG-NAA are produced by B2 cells that have escaped tolerance mechanisms and we show how such pathogenic IgG-NAA are regulated to prevent autoimmune disease. The Fc region of IgG-NAA can influence inflammation and B cell function in vivo by binding to activating and inhibitory FcγR. IgM-NAA has therapeutic potential. Polyclonal IgM infusions can be used to abrogate on-going inflammation. Additionally, inflammation arising after ischemic kidney injury, e.g., during high-risk elective cardiac surgery or after allograft transplantation, can be prevented by pre-emptively infusing polyclonal IgM or DC pretreated ex vivo with IgM or by increasing in vivo IgM with a vaccine approach. Cell therapy is appealing as less IgM will be required.

Natural IgM Switches the Function of Lipopolysaccharide-Activated Murine Bone Marrow-Derived Dendritic Cells to a Regulatory Dendritic Cell That Suppresses Innate Inflammation

We have previously shown that polyclonal natural IgM protects mice from renal ischemia/reperfusion injury (IRI) by inhibiting the reperfusion inflammatory response. We hypothesized that a potential mechanism involved IgM modulation of dendritic cells (DC), as we observed high IgM binding to splenic DC. To test this hypothesis, we pretreated bone marrow-derived DC (BMDC) with polyclonal murine or human IgM prior to LPS activation and demonstrated that 0.5 × 10(6) IgM/LPS-pretreated BMDC, when injected into wild-type C57BL/6 mice 24 h before renal ischemia, protect mice from developing renal IRI. We show that this switching of LPS-activated BMDC to a regulatory phenotype requires modulation of BMDC function that is mediated by IgM binding to nonapoptotic BMDC receptors. Regulatory BMDC require IL-10 and programmed death 1 as well as downregulation of CD40 and p65 NF-κB phosphorylation to protect in renal IRI. Blocking the programmed death ligand 1 binding site just before i.v. injection of IgM/LPS-pretreated BMDC or using IL-10 knockout BMDC fails to induce protection. Similarly, IgM/LPS-pretreated BMDC are rendered nonprotective by increasing CD40 expression and phosphorylation of p65 NF-κB. How IgM/LPS regulatory BMDC suppress in vivo ischemia-induced innate inflammation remains to be determined. However, we show that suppression is dependent on other in vivo regulatory mechanisms in the host, that is, CD25(+) T cells, B cells, IL-10, and circulating IgM. There was no increase in Foxp3(+) regulatory T cells in the spleen either before or after renal IRI. Collectively, these findings show that natural IgM anti-leukocyte Abs can switch BMDC to a regulatory phenotype despite the presence of LPS that ordinarily induces BMDC maturation.

Sialylation of N-linked glycans influences the immunomodulatory effects of IgM on T cells

Human serum IgM Abs are composed of heavily glycosylated polymers with five glycosylation sites on the μ (heavy) chain and one glycosylation site on the J chain. In contrast to IgG glycans, which are vital for a number of biological functions, virtually nothing is known about structure-function relationships of IgM glycans. Natural IgM is the earliest Ig produced and recognizes multiple Ags with low affinity, whereas immune IgM is induced by Ag exposure and is characterized by a higher Ag specificity. Natural anti-lymphocyte IgM is present in the serum of healthy individuals and increases in inflammatory conditions. It is able to inhibit T cell activation, but the underlying molecular mechanism is not understood. In this study, to our knowledge, we show for the first time that sialylated N-linked glycans induce the internalization of IgM by T cells, which in turn causes severe inhibition of T cell responses. The absence of sialic acid residues abolishes these inhibitory activities, showing a key role of sialylated N-glycans in inducing the IgM-mediated immune suppression.

Natural IgM anti-leucocyte autoantibodies (IgM-ALA) regulate inflammation induced by innate and adaptive immune mechanisms

Little is known about the function of natural IgM autoantibodies, especially that of IgM anti-leukocyte autoantibodies (IgM-ALA). Natural IgM-ALA are present at birth and characteristically increase during inflammatory and infective conditions. Our prior clinical observations and those of other investigators showing fewer rejections in renal and cardiac allografts transplanted into recipients with high levels of IgM-ALA led us to investigate whether IgM-ALA regulate the inflammatory response. In this review, we show that IgM, in physiologic doses, inhibit pro-inflammatory cell function in-vitro. We also show in an IgM knockout murine model, with intact B cells and regulatory T cells, that there is more severe inflammation and loss of function in the absence of IgM after renal ischemia reperfusion injury and cardiac allograft rejection. Replenishing IgM in IgM knockout mice or increasing the levels of IgM-ALA in wild-type B6 mice significantly attenuated the inflammation in both of these inflammatory models that involve IFN-γ and IL-17. The protective effect on renal ischemia reperfusion injury Is mediated by IgM ALA as protection was lost when using IgM pre-adsorbed with leukocytes to remove IgM-ALA. We provide data to show that the anti-inflammatory effect of IgM is mediated, in part, by inhibiting TLR-4-induced NF-κB translocation into the nucleus and inhibiting differentiation of activated T cells into Th-1 and Th-17 cells. In additional studies, we also show that intra-peritoneal administration of IgM prevents NOD mice from developing autoimmune insulitis which also involves Th-1 and Th-17 cells. These observations highlight the importance of IgM-ALA in regulating excess inflammation mediated by both innate and adaptive immune mechanisms and where the inflammatory response involves Th-17 cells that are not effectively regulated by T regs, B regs, and IL-10. IgM-ALA may in part regulate inflammation by altering dendritic cell function, as dendritic cells pre-treated in-vitro with polyclonal IgM protected mice from renal IRI. The latter findings may have relevance for cell-based therapy.

Induction of antinuclear antibodies by de novo autoimmune hepatitis regulates alloimmune responses in rat liver transplantation

Concanavalin A (Con A) is a lectin originating from the jack-bean and well known for its ability to stimulate T cells and induce autoimmune hepatitis. We previously demonstrated the induction of immunosuppressive antinuclear autoantibody in the course of Con A-induced transient autoimmune hepatitis. This study aimed to clarify the effects of Con A-induced hepatitis on liver allograft rejection and acceptance. In this study, we observed the unique phenomenon that the induction of transient de novo autoimmune hepatitis by Con A injection paradoxically overcomes the rejection without any immunosuppressive drug and exhibits significantly prolonged survival after orthotopic liver transplantation (OLT). Significantly increased titers of anti-nuclear Abs against histone H1 and high-mobility group box 1 (HMGB1) and reduced donor specific alloantibody response were observed in Con A-injected recipients. Induction of Foxp3 and IL-10 in OLT livers of Con A-injected recipients suggested the involvement of regulatory T cells in this unique phenomenon. Our present data suggest the significance of autoimmune responses against nuclear histone H1 and HMGB1 for competing allogeneic immune responses, resulting in the acceptance of liver allografts in experimental liver transplantation.

Nuclear antigens and auto/alloantibody responses: friend or foe in transplant immunology

In addition to cellular immune responses, humoral immune responses, mediated by natural antibodies, autoantibodies, and alloantibodies, have increasingly been recognized as causes of organ transplant rejection. In our previous studies, we have demonstrated the induction of antinuclear antibodies against histone H1 and high-mobility group box 1 (HMGB1), in both experimental and clinical liver transplant tolerance. The active induction of antinuclear antibodies is usually an undesirable phenomenon, but it is often observed after liver transplantation. However, the release of nuclear antigens and its suppression by neutralizing antibodies are proposed to be important in the initiation and regulation of immune responses. In this review article, we summarize the current understanding of nuclear antigens and corresponding antinuclear regulatory antibodies (Abregs) on infection, injury, inflammation, transplant rejection, and tolerance induction and discuss the significance of nuclear antigens as diagnostic and therapeutic targets.