Sphingosine-1 phosphate receptor 1 (S1PR1) is expressed by lymphocytes and regulates their egress from secondary lymphoid organs. Innate lymphoid cell (ILC) family has been expanded with the discovery of group 1, 2 and 3 ILCs, namely ILC1, ILC2 and ILC3. ILC3 and ILC1 have remarkable similarity to CD4+ helper T cell lineage members Th17 and Th1, respectively, which are important in the pathology of multiple sclerosis (MS). Whether human ILC subsets express S1PR1 or respond to its ligands have not been studied. In this study, we used peripheral blood/cord blood and tonsil lymphocytes as a source of human ILCs. We show that human ILCs express S1PR1 mRNA and protein and migrate toward S1P receptor ligands. Comparison of peripheral blood ILC numbers between fingolimod-receiving and treatment-free MS patients revealed that, in vivo , ILCs respond to fingolimod, an S1PR1 agonist, resulting in ILC-penia in circulation. Similarly, murine ILCs responded to fingolimod by exiting blood and accumulating in the secondary lymph nodes. Importantly, ex vivo exposure of ILC3 and ILC1 to fingolimod or SEW2871, another S1PR1 antagonist, reduced production of ILC3- and ILC1- associated cytokines GM-CSF, IL-22, IL-17, and IFN-γ, respectively. Surprisingly, despite reduced number of lamina propria-resident ILC3s in the long-term fingolimod-treated mice, ILC3-associated IL-22, IL-17A, GM-CSF and antimicrobial peptides were high in the gut compared to controls, suggesting that its long term use may not compromise mucosal barrier function. To our knowledge, this is the first study to investigate the impact of fingolimod on human ILC subsets in vivo and ex vivo , and provides insight into the impact of long term fingolimod use on ILC populations.

The capping protein regulator and myosin 1 linker 2 (CARMIL2) deficiency is an autosomal recessive inborn error of immunity (IEI) leading to combined T-cell, B-cell, and NK cell defects. 1,2 CARMIL2, also known as RGD motif, leucine-rich repeats, tropomodulin domain, and proline-rich containing protein (RLTPR), is a member of the CARMIL family. This family consists of three paralogous genes (CARMIL1, CARMIL2, and CARMIL3), producing multidomain proteins with high sequence homology. They contain an N-terminal pleckstrin homology (PH) domain, a leucine-rich repeat (LRR) domain, a homodimerization domain (HD), and a C-terminal domain including a capping protein binding region (CBR) and a proline-rich region (PRR).While all CARMILs have a capacity to bind to the capping proteins and regulate actin assembly, each protein also has a unique cellular function. 3 CARMIL1 activates the Trio-Rac1 pathway to enhance Arp2/3-mediated actin polymerization, 4,5 whereas CARMIL2 binds to cellular membranes via vimentin, and activates T cells by ligating CD28 and CARMA1 to mediate NFk B signaling. 6,7 Mice expressing mutated Carmil2 gene are not able to conduct CD28-mediated activation of its effector protein kinase C theta (PKCθ), abrogating effector memory CD4 + T and regulatory T cells (Treg) development. 7,8 CARMIL2 is also necessary for invadopodia formation, cell polarity, lamellipodial assembly, membrane ruffling, macropinocytosis, and cell migration. 3 The CARMIL3 is expressed mainly in the brain and spinal cord, and identified as oncofetal gene; however, recently, it was demonstrated as essential regulator of the proinflammatory cytokines in macrophages. 3,9 The human CARMIL2 gene was originally identified by Matsuzaka et al. and shown to be downregulated in affected skin cells of psoriasis vulgaris patients. 10 The CARMIL2 protein is expressed in the cytoplasm, especially in the skin, lymphoid tissue, and gastrointestinal system, and was demonstrated to play a role in wound healing. 3 So far, fewer than 40 cases of CARMIL2 deficiency have been reported worldwide. Patients with CARMIL2 deficiency present with a broad range of symptoms, including cutaneous and respiratory allergies mainly characterized by eczematous lesions, early-onset

Background: Dedicator of cytokinesis 8 (DOCK8) deficiency is the main cause of the autosomal recessive hyper-IgE syndrome (HIES). We previously reported the selective loss of group 3 innate lymphoid cell (ILC) number and function in a Dock8-deficient 922 | EKEN Et al.

Mucositis is a common side effect of cancer therapies and transplant conditioning regimens. Management of mucositis involves multiple approaches from oral hygiene, antiinflammatory, anti-apoptotic, cytoprotective, and antioxidant agents, to cryo-therapy, physical therapy, and growth factors. There is room for novel, affordable treatment options, or improvement of currently available therapies. Vitamin D has been shown to regulate mucosa-resident cell populations such as Th17 or innate lymphoid cells and critical mucosal cytokine IL-22; however, their therapeutic potential has not been put to test in preclinical mouse models. In this study, we aimed to test the therapeutic potential of vitamin D injections and IL-22 overexpression in a murine model of chemotherapy-induced mucositis. Balb/c mice were given daily intraperitoneal injections of vitamin D. Mucositis was induced by methotrexate. Another group received IL-22 plasmid via hydrodynamic gene delivery. Weight loss and intestinal histopathology, intestinal levels of cytokines IL-22, IL-17A, GM-CSF, IL-23, IFN-γ, TNF-α, and IL-10, and number of intestinal lamina propria B cell, neutrophil, and total innate lymphoid cells were quantified. Daily vitamin D injections ameliorated intestinal inflammation and elevated intestinal IL-22 levels compared with control groups. Temporal overexpression of IL-22 by hydrodynamic gene delivery slightly increased intestinal IL-22 but failed to confer significant protection from mucositis. To our knowledge, this is the first experimental demonstration in an animal model of mucositis of therapeutic use of vitamin D and IL-22 supplementation and our results with vitamin D suggest it may have merit in further trials in human mucositis patients.

IL‐22 is an alpha‐helical cytokine which belongs to the IL‐10 family of cytokines. IL‐22 is produced by RORγt+ innate and adaptive lymphocytes, including ILC3, γδ T, iNKT, Th17 and Th22 cells and some granulocytes. IL‐22 receptor is expressed primarily by non‐haematopoietic cells. IL‐22 is critical for barrier immunity at the mucosal surfaces in the steady state and during infection. Although IL‐22 knockout mice were previously shown to develop experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), how temporal IL‐22 manipulation in adult mice would affect EAE course has not been studied previously. In this study, we overexpressed IL‐22 via hydrodynamic gene delivery or blocked it via neutralizing antibodies in C57BL/6 mice to explore the therapeutic impact of IL‐22 modulation on the EAE course. IL‐22 overexpression significantly decreased EAE scores and demyelination, and reduced infiltration of IFN‐γ+IL‐17A+Th17 cells into the central nervous system (CNS). The neutralization of IL‐22 did not alter the EAE pathology significantly. We show that IL‐22‐mediated protection is independent of Reg3γ, an epithelial cell‐derived antimicrobial peptide induced by IL‐22. Thus, overexpression of Reg3γ significantly exacerbated EAE scores, demyelination and infiltration of IFN‐γ+IL‐17A+ and IL‐17A+GM‐CSF+Th17 cells to CNS. We also show that Reg3γ may inhibit IL‐2‐mediated STAT5 signalling and impair expansion of Treg cells in vivo and in vitro. Finally, Reg3γ overexpression dramatically impacted intestinal microbiota during EAE. Our results provide novel insight into the role of IL‐22 and IL‐22‐induced antimicrobial peptide Reg3γ in the pathogenesis of CNS inflammation in a murine model of MS.