Vitiligo is a chronic autoimmune depigmenting skin disorder that results from a loss of melanocytes. Multiple combinatorial factors have been involved in disease development, with a prominent role of the immune system, in particular T cells. After repigmentation, vitiligo frequently recurs in the same area, suggesting that vitiligo could involve the presence of resident memory T cells (T). We sought to perform a thorough characterization of the phenotype and function of skin memory T cells in vitiligo. We show that stable and active vitiligo perilesional skin is enriched with a population of CD8 T expressing both CD69 and CD103 compared with psoriasis and control unaffected skin. CD8 T expressing CD103 are mainly localized in the epidermis. Expression of CXCR3 is observed on most CD8 T in vitiligo, including the population of melanocyte-specific CD8 T cells. CD8 T displayed increased production of IFN-γ and tumor necrosis factor-α with moderate cytotoxic activity. Our study highlights the presence of functional CD8 T in both stable and active vitiligo, reinforcing the concept of vitiligo as an immune memory skin disease. The CD8 T that remain in stable disease could play a role during disease flares, emphasizing the interest in targeting this cell subset in vitiligo.

The immune system is necessary for protecting against various pathogens. However, under certain circumstances, self-reactive immune cells can drive autoimmunity, like that exhibited in type 1 diabetes (T1D). CD4+ T cells are major contributors to the immunopathology in T1D, and in order to drive optimal T cell activation, third signal reactive oxygen species (ROS) must be present. However, the role ROS play in mediating this process remains to be further understood. Recently, cellular metabolic programs have been shown to dictate the function and fate of immune cells, including CD4+ T cells. During activation, CD4+ T cells must transition metabolically from oxidative phosphorylation to aerobic glycolysis to support proliferation and effector function. As ROS are capable of modulating cellular metabolism in other models, we sought to understand if blocking ROS also regulates CD4+ T cell activation and effector function by modulating T cell metabolism. To do so, we utilized an ROS scavenging and potent antioxidant manganese metalloporphyrin (MnP). Our results demonstrate that redox modulation during activation regulates the mTOR/AMPK axis by maintaining AMPK activation, resulting in diminished mTOR activation and reduced transition to aerobic glycolysis in diabetogenic splenocytes. These results correlated with decreased Myc and Glut1 upregulation, reduced glucose uptake, and diminished lactate production. In an adoptive transfer model of T1D, animals treated with MnP demonstrated delayed diabetes progression, concurrent with reduced CD4+ T cell activation. Our results demonstrate that ROS are required for driving and sustaining T cell activation-induced metabolic reprogramming, and further support ROS as a target to minimize aberrant immune responses in autoimmunity.

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Highlights d LAG-3 limits CD4 + T cell oxygen consumption and spare respiratory capacity (SRC) d Naive CD4 + T cells utilize their SRC to support spontaneous proliferation d LAG-3 regulates STAT5 and Akt activation d Lag3 À/À CD4 + T cells are less dependent upon IL-7 for survival and metabolism

Vitiligo is an autoimmune disease that results from the loss of melanocytes, associated with skin infiltration of CD8 þ effector memory T cells with a Tc1 skewed immune response. NKG2D is an activating receptor found on immune cells, in particular natural killer and activated CD8 þ T cells, that are able to produce a high amount of IFN-g. Here we found that NKG2D expression was increased in vitiligo skin CD8 þ effector memory T cells and was promoted by IL-15. Phenotypic and functional analyses showed that NKG2D þ CD8 þ skin effector memory T cells displayed an activated phenotype and produced elevated levels of both IFN-g and tumor necrosis factor-a. Additional experiments revealed that vitiligo skin dendritic cells expressed the NKG2D ligands MICA-MICB, and in vitro experiments showed that these ligands could be induced on dendritic cells by IFN-a. Cultures of IFN-aestimulated dendritic cells with skin NKG2D þ CD8 þ T cells potentiated the production of type 1 cytokines, which was next inhibited by blocking the NKG2D/MICA-MICB interaction. These data show that NKG2D is a potential marker of pathogenic skin CD8 þ effector memory T cells during vitiligo. Therefore, targeting NKG2D could be an attractive strategy in vitiligo, a disease for which there is a strong need of innovative treatments.

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In Type 1 Diabetes (T1D), CD4+ T cells initiate autoimmune attack of pancreatic islet β cells. Importantly, bioenergetic programs dictate T cell function, with specific pathways required for progression through the T cell lifecycle. During activation, CD4+ T cells undergo metabolic reprogramming to the less efficient aerobic glycolysis, similarly to highly proliferative cancer cells. In an effort to limit tumor growth in cancer, use of glycolytic inhibitors have been successfully employed in preclinical and clinical studies. This strategy has also been utilized to suppress T cell responses in autoimmune diseases like Systemic Lupus Erythematosus (SLE), Multiple Sclerosis (MS), and Rheumatoid Arthritis (RA). However, modulating T cell metabolism in the context of T1D has remained an understudied therapeutic opportunity. In this study, we utilized the small molecule PFK15, a competitive inhibitor of the rate limiting glycolysis enzyme 6-phosphofructo-2-kinase/fructose-2,6- biphosphatase 3 (PFKFB3). Our results confirmed PFK15 inhibited glycolysis utilization by diabetogenic CD4+ T cells and reduced T cell responses to β cell antigen in vitro. In an adoptive transfer model of T1D, PFK15 treatment delayed diabetes onset, with 57% of animals remaining euglycemic at the end of the study period. Protection was due to induction of a hyporesponsive T cell phenotype, characterized by increased and sustained expression of the checkpoint molecules PD-1 and LAG-3 and downstream functional and metabolic exhaustion. Glycolysis inhibition terminally exhausted diabetogenic CD4+ T cells, which was irreversible through restimulation or checkpoint blockade in vitro and in vivo. In sum, our results demonstrate a novel therapeutic strategy to control aberrant T cell responses by exploiting the metabolic reprogramming of these cells during T1D. Moreover, the data presented here highlight a key role for nutrient availability in fueling T cell function and has implications in our understanding of T cell biology in chronic infection, cancer, and autoimmunity.