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

Factors Governing B Cell Recognition of Autoantigen and Function in Type 1 Diabetes

Islet autoantibodies predict type 1 diabetes (T1D) but can be transient in murine and human T1D and are not thought to be directly pathogenic. Rather, these autoantibodies signal B cell activity as antigen-presenting cells (APCs) that present islet autoantigen to diabetogenic T cells to promote T1D pathogenesis. Disrupting B cell APC function prevents T1D in mouse models and has shown promise in clinical trials. Autoantigen-specific B cells thus hold potential as sophisticated T1D biomarkers and therapeutic targets. B cell receptor (BCR) somatic hypermutation is a mechanism by which B cells increase affinity for islet autoantigen. High-affinity B and T cell responses are selected in protective immune responses, but immune tolerance mechanisms are known to censor highly autoreactive clones in autoimmunity, including T1D. Thus, different selection rules often apply to autoimmune disease settings (as opposed to protective host immunity), where different autoantigen affinity ceilings are tolerated based on variations in host genetics and environment. This review will explore what is currently known regarding B cell signaling, selection, and interaction with T cells to promote T1D pathogenesis.

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.

NOD Mice Recapitulate the Cardiac Disturbances Observed in Type 1 Diabetes

This work aimed at testing the hypothesis that NOD/ShiLtJ mice (NOD) recapitulate the cardiac disturbances observed on type 1 diabetes (T1D). NOD mice were studied 4 weeks after the onset of hyperglycemia, and NOR/Lt mice matched as control. Cardiac function was evaluated by echocardiography and electrocardiography (ECG). Action potentials (AP) and Ca2+ transients were evaluated at whole heart level. Heart mitochondrial function was evaluated by high-resolution respirometry and H2O2 release. NOD mice presented a reduction in hearth weight. Mitochondrial oxygen fluxes and H2O2 release were similar between NOD and NOR mice. ECG revealed a QJ interval prolongation in NOD mice. Furthermore, AP duration at 30% of repolarization was increased, and it depicted slower Ca2+ transient kinetics. NOD mice presented greater number/severity of ventricular arrhythmias both in vivo and in vitro. In conclusion, NOD mice evoked cardiac electrical and calcium handling disturbances similar to the observed in T1D. Graphical Abstract .

Microencapsulated G3C Hybridoma Cell Graft Delays the Onset of Spontaneous Diabetes in NOD Mice by an Expansion of Gitr+ Treg Cells

As an alternative to lifelong insulin supplementation, potentiation of immune tolerance in patients with type 1 diabetes could prevent the autoimmune destruction of pancreatic islet β-cells. This study was aimed to assess whether the G3c monoclonal antibody (mAb), which triggers the glucocorticoid-induced TNFR-related (Gitr) costimulatory receptor, promotes the expansion of regulatory T cells (Tregs) in SV129 (wild-type) and diabetic-prone NOD mice. The delivery of the G3c mAb via G3C hybridoma cells enveloped in alginate-based microcapsules (G3C/cps) for 3 weeks induced Foxp3⁺ Treg-cell expansion in the spleen of wild-type mice but not in Gitr^-/- mice. G3C/cps also induced the expansion of nonconventional Cd4⁺Cd25^-/lowFoxp3^lowGitr^int/high (GITR single-positive [sp]) Tregs. Both Cd4⁺Cd25⁺Gitr^highFoxp3⁺ and GITRsp Tregs (including also antigen-specific cells) were expanded in the spleen and pancreas of G3C/cps-treated NOD mice, and the number of intact islets was higher in G3C/cps-treated than in empty cps-treated and untreated animals. Consequently, all but two G3C/cps-treated mice did not develop diabetes and all but one survived until the end of the 24-week study. In conclusion, long-term Gitr triggering induces Treg expansion, thereby delaying/preventing diabetes development in NOD mice. This therapeutic approach may have promising clinical potential for the treatment of inflammatory and autoimmune diseases.