Apoptotic non-beta cells suppress beta cell antigen-reactive T cells and induce beta cell antigen-specific regulatory T cells

Vitamin D-independent benefits of safe sunlight exposure

This review examines the beneficial effects of ultraviolet radiation on systemic autoimmune diseases, including multiple sclerosis and type I diabetes, where the epidemiological evidence for the vitamin D-independent effects of sunlight is most apparent. Ultraviolet radiation, in addition to its role in the synthesis of vitamin D, stimulates anti-inflammatory pathways, alters the composition of dendritic cells, T cells, and T regulatory cells, and induces nitric oxide synthase and heme oxygenase metabolic pathways, which may directly or indirectly mitigate disease progression and susceptibility. Recent work has also explored how the immune-modulating functions of ultraviolet radiation affect type II diabetes, cancer, and the current global pandemic caused by SARS-CoV-2. These diseases are particularly important amidst global changes in lifestyle that result in unhealthy eating, increased sedentary habits, and alcohol and tobacco consumption. Compelling epidemiological data shows increased ultraviolet radiation associated with reduced rates of certain cancers, such as colorectal cancer, breast cancer, non-Hodgkins lymphoma, and ultraviolet radiation exposure correlated with susceptibility and mortality rates of COVID-19. Therefore, understanding the effects of ultraviolet radiation on both vitamin D-dependent and -independent pathways is necessary to understand how they influence the course of many human diseases.

Generation of antigen-specific Foxp3+ regulatory T-cells in vivo following administration of diabetes-reversing tolerogenic microspheres does not require provision of antigen in the formulation

We have developed novel antisense oligonucleotide-formulated microspheres that can reverse hyperglycemia in newly-onset diabetic mice. Dendritic cells taking up the microspheres adopt a restrained co-stimulation ability and migrate to the pancreatic lymph nodes when injected into an abdominal region that is drained by those lymph nodes. Furthermore, we demonstrate that the absolute numbers of antigen-specific Foxp3+ T regulatory cells are increased only in the lymph nodes draining the site of administration and that these T-cells proliferate independently of antigen supply in the microspheres. Taken together, our data add to the emerging model where antigen supply may not be a requirement in "vaccines" for autoimmune disease, but the site of administration - subserved by lymph nodes draining the target organ - is in fact critical to foster the generation of antigen-specific regulatory cells. The implications of these observations on "vaccine" design for autoimmunity are discussed and summarized.

Apoptotic dendritic cells induce tolerance in mice through suppression of dendritic cell maturation and induction of antigen-specific regulatory T cells

Dendritic cell (DC) apoptosis has been shown to play a role in maintaining a balance between tolerance and immunity. However, the mechanisms of how DC apoptosis affects the immune response are unclear. We have shown that in vitro culture of apoptotic DCs with immature DCs, results in their uptake by immature DCs, which subsequently turn into tolerogenic DCs, which then secrete TGF-beta1 and induce Foxp3(+) regulatory T cells (T(regs)). In this study we looked at the effects of apoptotic DCs in vivo. Here we show that apoptotic DCs are taken up by viable DCs in vivo, which suppresses the ability of viable DCs to undergo maturation and subsequent migration to the lymph nodes in response to LPS. Additionally, delivery of apoptotic DCs to LPS inflamed lungs results in resolution of inflammation, which is mediated by the ability of apoptotic DCs to suppress response of viable DCs to LPS. Additionally, apoptotic DCs also induce TGF-beta1 secretion in the mediastinal lymph nodes, which results in expansion of Foxp3(+) T(regs). Most importantly, we show that delivery of apoptotic DCs followed by OVA in CFA to mice suppresses T cell response to OVA and instead induces de novo generation of OVA-specific T(regs). Furthermore, delivery of apoptotic DCs followed by OVA in CFA results in expansion of T(regs) in TCR transgenic (OT-II) mice. These findings demonstrate that apoptotic DCs are taken up by viable DCs in vivo, which promotes tolerance through suppression of DC maturation and induction of T(regs).