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Neutrophils were long considered to be a short-lived homogenous cell population, limited to their role as first responders in anti-bacterial and -fungal immunity. While it is true that neutrophils are first to infiltrate the site of infection to eliminate pathogens, growing evidence suggests their functions could extend beyond those of basic innate immune cells. Along with their well-established role in pathogen elimination, utilizing effector functions such as phagocytosis, degranulation, and the deployment of neutrophil extracellular traps (NETs), neutrophils have recently been shown to possess antigen-presenting capabilities. Moreover, the identification of different subtypes of neutrophils points to a multifactorial heterogeneous cell population with great plasticity in which some subsets have enhanced pro-inflammatory characteristics, while others seem to behave as immunosuppressors. Interestingly, the aberrant presence of activated neutrophils with a pro-inflammatory profile in several systemic and organ-specific autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), multiple sclerosis (MS), and type 1 diabetes (T1D) could potentially be exploited in novel therapeutic strategies. The full extent of the involvement of neutrophils, and more specifically that of their various subtypes, in the pathophysiology of autoimmune diseases is yet to be elucidated., (© The Author(s) 2022. Published by Oxford University Press on behalf of the British Society for Immunology.)

Thyroid hormones (THs) are crucial regulators of glucose metabolism and insulin sensitivity. Moreover, inactivating mutations in type 2 deiodinase (DIO2), the major TH-activating enzyme, have been associated with type 2 diabetes mellitus in both humans and mice. We studied the link between Dio2 deficiency and glucose homeostasis in fasted males of two different Dio2 knockout (KO) zebrafish lines. Young adult Dio2KO zebrafish (6 to 9 months) were hyperglycemic. Both insulin and glucagon expression were increased, whereas β and α cell numbers in the main pancreatic islet were similar to those in wild-types. Insulin receptor expression in skeletal muscle was decreased at 6 months, accompanied by a strong downregulation of hexokinase and pyruvate kinase expression. Blood glucose levels in Dio2KO zebrafish, however, normalized around 1 year of age. Older mutants (18 to 24 months) were normoglycemic, and increased insulin and glucagon expression was accompanied by a prominent increase in pancreatic islet size and β and α cell numbers. Older Dio2KO zebrafish also showed strongly decreased expression of glucagon receptors in the gastrointestinal system as well as decreased expression of glucose transporters GLUT2 and GLUT12, glucose-6-phosphatase, and glycogen synthase 2. This study shows that Dio2KO zebrafish suffer from transient hyperglycemia, which is counteracted with increasing age by a prominent hyperplasia of the endocrine pancreas together with decreases in hepatic glucagon sensitivity and intestinal glucose uptake. Further research on the mechanisms allowing compensation in older Dio2KO zebrafish may help to identify new therapeutic targets for (TH deficiency-related) hyperglycemia., (Copyright © 2019 Endocrine Society.)

Inflammatory bowel diseases are gastrointestinal diseases that include Crohn disease and ulcerative colitis. The chronic inflammation is thought to result from an excessive inflammatory response to environmental factors such as luminal bacteria in genetically predisposed individuals. Studies have revealed that mice with impaired vitamin D signaling are more susceptible to experimental colitis. To better understand the contribution of vitamin D signaling in different cells of the gut to this disease, we investigated the effects of intestinal-specific or myeloid vitamin D receptor deletion. Our study addressed the importance of vitamin D receptor expression in intestinal epithelial cells using intestine-specific vitamin D receptor null mice and the contribution of vitamin D receptor expression in macrophages and granulocytes using myeloid-specific vitamin D receptor null mice in a dextran sodium sulfate model for experimental colitis. Loss of intestinal vitamin D receptor expression had no substantial effect on the clinical parameters of colitis and did not manifestly change mucosal cytokine expression. Inactivation of the vitamin D receptor in macrophages and granulocytes marginally affected colitis-associated symptoms but resulted in increased proinflammatory cytokine and increased β-defensin-1 expression in the colon descendens of mice with colitis. Intestinal deletion of the vitamin D receptor did not aggravate symptoms of chemically induced colitis. Loss of the vitamin D receptor in macrophages and granulocytes mildly affected colitis-associated symptoms but greatly increased proinflammatory cytokine expression in the inflamed colon, suggesting a prominent role for innate immune cell vitamin D signaling in controlling gut inflammation., (Copyright © 2017 Endocrine Society.)

Pancreatic endocrine progenitors obtained from human embryonic stem cells (hESCs) represent a promising source to develop cell-based therapies for diabetes. Although endocrine pancreas progenitor cells have been isolated from mouse pancreata on the basis of Ngn3 expression, human endocrine progenitors have not been isolated yet. As substantial differences exist between human and murine pancreas biology, we investigated whether it is possible to isolate pancreatic endocrine progenitors from differentiating hESC cultures by lineage tracing of NGN3. We targeted the 3' end of NGN3 using zinc finger nuclease-mediated homologous recombination to allow selection of NGN3eGFP(+) cells without disrupting the coding sequence of the gene. Isolated NGN3eGFP(+) cells express PDX1, NKX6.1, and chromogranin A and differentiate in vivo toward insulin, glucagon, and somatostatin single hormone-expressing cells but not to ductal or exocrine pancreatic cells or other endodermal, mesodermal, or ectodermal lineages. This confirms that NGN3(+) cells represent pancreatic endocrine progenitors in humans. In addition, this hESC reporter line constitutes a unique tool that may aid in gaining insight into the developmental mechanisms underlying fate choices in human pancreas and in developing cell-based therapies.

Vitamin D exerts important regulatory effects on the endocrine and immune systems. Autoimmune type 1 diabetes (T1D) development in the inbred NOD mouse strain can be accelerated by vitamin D insufficiency or suppressed by chronic treatment with high levels of 1α,25-dihydroxyvitamin D(3). Consequently, a report that T1D development was unaffected in NOD mice genetically lacking the vitamin D receptor (VDR) was unexpected. To further assess this result, the mutant stock was imported to The Jackson Laboratory, backcrossed once to NOD/ShiLtJ, and progeny rederived through embryo transfer. VDR-deficient NOD mice of both sexes showed significant acceleration of T1D. This acceleration was not associated with alterations in immune cells targeting pancreatic β-cells. Rather, the capacity of β-cells to produce and/or secrete insulin was severely impaired by the hypocalcaemia developing in VDR-deficient NOD mice fed a standard rodent chow diet. Feeding a high-lactose calcium rescue diet that circumvents a VDR requirement for calcium absorption from the intestine normalized serum calcium levels, restored β-cell insulin secretion, corrected glucose intolerance, and eliminated accelerated T1D in VDR-deficient NOD mice. These findings suggest that calcium and/or vitamin D supplementation may improve disease outcomes in some T1D-prone individuals that are calcium deficient.

Vitamin D homeostasis in the immune system is the focus of this review. The production of both the activating (25- and 1alpha-hydroxylase) and the metabolizing (24-hydroxylase) enzymes by cells of the immune system itself, indicates that 1,25(OH)(2)D(3) can be produced locally in immune reaction sites. Moreover, the strict regulation of these enzymes by immune signals is highly suggestive for an autocrine/paracrine role in the immune system, and opens new treatment possibilities.

Mice with a disrupted IFN-gamma system are remarkably susceptible to experimental autoimmune diseases, such as collagen-induced arthritis (CIA), which rely on the use of CFA. The inflammatory lesions of these IFN-gamma knockout (KO) mice are characterized by an excessive proportion of neutrophils. Here, we show that the increased severity of CIA in IFN-gammaR KO as compared with wild-type mice is accompanied by increased levels of the CXC chemokine granulocyte chemotactic protein-2 (GCP-2), a major neutrophil-attracting chemokine in mice. We demonstrated that the heat-killed mycobacteria present in CFA elicited production of GCP-2 in mouse embryo fibroblast cultures and that this production was inhibited by IFN-gamma. Inhibition of GCP-2 production by IFN-gamma was STAT-1-dependent. IFN-gamma receptor KO mice treated with neutralizing anti-GCP-2 antibodies were protected from CIA, indicating the in vivo importance of GCP-2 in the pathogenesis of CIA. Our data support the notion that one of the mechanisms whereby endogenous IFN-gamma mitigates the manifestations of CIA consists of inhibiting production of GCP-2, thereby limiting mobilization and infiltration of neutrophils, which are important actors in joint inflammation. These results may also be applicable to other experimental models of autoimmunity that rely on the use of CFA.

Autoimmune diabetes recurrence is in part responsible for islet graft destruction in type 1 diabetic individuals. The aim of the present study was to design treatment modalities able to prevent autoimmune diabetes recurrence after islet transplantation in spontaneously diabetic NOD mice. In order to avoid confusion between autoimmune diabetes recurrence and allograft rejection, we performed syngeneic islet transplantations in spontaneously diabetic NOD mice. Mice were treated with mouse interferon-beta (IFN-beta, 1 x 105 IU/day), a new 14-epi-1,25-(OH)2D3-analogue (TX 527, 5 microg/kg/day) and cyclosporin A (CsA, 7.5 mg/kg/day) as single substances and in combinations. Treatment was stopped either 20 days (IFN-beta and CsA) or 30 days (TX 527) after transplantation. Autoimmune diabetes recurred in 100% of control mice (MST 11 days). None of the mono-therapies significantly prolonged islet graft survival. Combining CsA with TX 527 maintained graft function in 67% of recipients as long as treatment was given (MST 31 days, P < 0.01 versus controls). Interestingly, 100% of the IFN-beta plus TX 527-treated mice had normal blood glucose levels during treatment, and even had a more pronounced prolongation of graft survival (MST 62 days, P < 0.005 versus controls). Cytokine mRNA analysis of the grafts 6 days after transplantation revealed a significant decrease in IL-2, IFN-gamma and IL-12 messages in both IFN-beta plus TX 527- and CsA plus TX 527-treated mice, while only in the IFN-beta with TX 527 group were higher levels of IL-10 transcripts observed. Therefore, we conclude that a combination of IFN-beta and TX 527 delays autoimmune diabetes recurrence in islet grafts in spontaneously diabetic NOD mice.

Introduction of the hu-PBL-SCID mouse model has yielded a potentially useful tool for research in transplantation. The aim of this study was to define the conditions necessary for a reconstituted human immune system to destroy in a consistent manner rat islet xenografts in the alloxan-diabetic hu-PBL-SCID mouse. We examined different time points of hu-PBL reconstitution, different transplantation sites of the islets and several hu-PBL reconstitution protocols. Major differences in graft destruction were observed between the different hu-PBL reconstitution protocols, irrespective of timing of hu-PBL reconstitution or site of transplantation. Although preactivation of hu-PBL did not improve the level of hu-PBL chimerism, histological and immunohistochemical analysis of the grafts revealed a severe human lymphocytic infiltration and beta cell destruction only in the grafts of mice receiving preactivated hu-PBL. This beta cell injury resulted in impaired glucose tolerance, with in some animals recurrence of hyperglycaemia, and decreased insulin and C-peptide levels after glucose stimulation. Therefore, we conclude that activation of hu-PBL prior to transfer is essential in achieving xenograft infiltration and destruction in hu-PBL-SCID mice. The need for immune manipulation suggests that interactions between hu-PBL and xenografts in this model may be hampered by incompatibilities in cross-species adhesion and/or activation signals.