A set of histopathological elements with death of epidermal basal cell layer keratinocytes along with inflammatory cell infiltration distinguishes lichenoid tissue reaction (LTR)/interface dermatitis (IFD) from other inflammatory mucocutaneous diseases. The LTR/IFD can be seen in skin disorders like as lichen planus, acute graft-versus-host disease, lupus erythematosus, dermatomyositis, and toxic epidermal necrolysis/Stevesn-Johnson syndrome. Clinical and basic researches suggested that cytotoxic CD8 T cells producing interferon-γ and FasL are final effector cells to cause apoptosis of keratinocyte. Some murine models of LTR/IFD have been established, for example, LTR/IFD reactions of keratinocyte-specific ovalbumin (OVA)-transgenic mice after OVA-specific T-cell-receptor⁺CD8 T cells. By analysis of the murine model, a new class of immunosuppressant, a JAK inhibitor, has been suggested as a new candidate for treatment of LTR/IFD.

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  IgG4-related disease (IgG4-RD) is a systemic inflammatory disorder that can affect most organs/tissues like sarcoidosis. The kidney is one of the most frequently affected organs. While tubulointerstitial nephritis (TIN) with characteristic imaging findings is the representative lesion of IgG4-related kidney disease (IgG4-RKD), a variety of glomerular lesions, particularly membranous nephropathy, sometimes overlap on TIN. Clinically, either decreased renal function and/or characteristic imaging findings such as multiple low-density lesions on contrast-enhanced computed tomography are typical presenting features. Histologically, plasma cell (PC)-rich TIN accompanied by characteristic fibrosis called storiform fibrosis with dense IgG4-positive PC infiltration is a typical finding. Although a swift response to corticosteroid is a very important feature of IgG4-RKD, in cases with moderately to severely decreased renal function before therapy, only partial recovery of renal function is obtained. This review provides a comprehensive overview of IgG4-RKD from the clinical, laboratory, imaging, and histological aspects and also addresses some of the therapeutic issues concerning it.

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  The bony skeleton enables the locomotive activity, the storage of calcium, and the harboring of the hematopoietic stem cells from which blood and immune cells are derived. The immune and skeletal systems share various molecules including cytokines, signaling molecules, transcription factors and membrane receptors. Investigation into rheumatoid arthritis (RA) as well as cloning of RANKL and various bone phenotypes found in immune-compromised gene deficient mice has highlighted the importance of the dynamic interplay between the both systems. These findings have recently led to both the emergence and subsequent rapid evolution of the field of osteoimmunology. The scope of osteoimmunology has been extended to encompass a wide range of molecular and cellular interactions, the elucidation of which will provide a scientific basis for future therapeutic approaches to diseases related to the immune and skeletal systems.

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  It has recently become clear that initial glomerular injury affects glomerular visceral epithelial cells (also called as podocytes) as important target cells for progression of chronic kidney disease (CKD) and end-stage kidney disease. Podocytes are injured in many human kidney diseases including minimal change disease, focal segmental glomerulosclerosis, diabetic nephropathy, membranous nephropathy and lupus nephritis. Podocytes are highly specialized epithelial cells that cover the outer layer of the glomerular basement membrane (GBM). Podocytes serve as the final barrier to urinary protein loss through the special formation and maintenance of foot-processes and an interposed slit-diaphragm. Chronic podocyte injury may cause podocyte detachment from the GBM, which leads to glomerulosclerosis. The elucidation of podocyte biology during the last 15 years has significantly improved our understanding of the pathophysiologic processes of proteinuria and glomerulosclerosis. In this review, we highlight some of new data including our recent findings for translating podocyte biology into new examinations and therapies for podocyte injury.

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  Niacin, also known as vitamin B3, is required for the synthesis of coenzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Niacin binds with G protein-coupled receptor (GPR) 109A on cutaneous Langerhans cells and causes vasodilation with flushing in head and neck area. Niacin deficiency due to excessive alcohol consumption, certain drugs or inadequate uptake in diet causes pellagra, a photosensitivity dermatitis. Recently several studies have revealed the mechanism of photosensitivity in niacin deficiency, which may pave a way for new therapeutic approaches. The expression level of prostaglandin E synthase (PTGES) is up-regulated in the skin of both pellagra patients and niacin deficient pellagra mouse models. In addition, pellagra is mediated through prostaglandin E₂-EP4 (PGE₂-EP4) signaling via reactive oxygen species (ROS) production in keratinocytes. In this article, we have reviewed the role of niacin in immunity and the mechanism of niacin deficiency-induced photosensitivity.

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  Rheumatoid arthritis (RA) affects mainly women during their childbearing years. As aging of childbirth advances in Japan, women who plan pregnancy would increase after they developed RA. Recent findings showed that high disease activity of RA might impair fertility. Planning pregnancy is preferable after female patients achive and maintain low disease activity or remission of RA. Women on methotrexate, which is the anchor drug for RA, need to discontinue the medication with a high risk of causing birth defects during conception and pregnancy. Data of RA patients exposed TNF inhibitors during pregnancy has been accumulating in recent years. These data suggest that increased risk of spontaneous abortion and congenital abnomalies has not been observed. Although there is insufficient data about safety of breastfeeding while using TNF inhibitors, the secretion of the drugs in breast milk is very little and fetal toxicity has not been observed. Since long term safety of children exposed TNF inhibitors in uterus has not been established, we should discontinue the drugs as soon as pregnancy is recognized. TNF inhibitors may be an useful tools for management of active RA resistant to conventional DMARDs in women who desire to bear children.

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  For a long time, it has been thinking that B cells regulate immune responses by producing antigen-specific antibodies. However, previous studies have revealed that specific B-cell subsets can also negatively regulate T-cell immune responses, and have been termed regulatory B cells. Recently, our study showed that mouse CD1d^hiCD5⁺ B cell subsets mainly produce IL-10. Therefore, we named these populations B10 cells. In our previous studies have also indicated that human B10 cells with the ability to express the inhibitory cytokine interleukin (IL)-10 have been identified. Although it is rare, B10 cells are potent negative regulators of antigen-specific inflammation and T-cell-dependent autoimmune diseases in mice. How B10-cell IL-10 production and regulation of antigen-specific immune responses are controlled in vivo without inducing systemic immunosuppression is unknown. Using an experimental autoimmune encephalomyelitis, which is a mouse model for multiple sclerosis, we have shown that B10-cell maturation into functional IL-10-secreting effector cells that inhibit in vivo autoimmune disease requires IL-21 and CD40-dependent cognate interactions with T cells. In addition, the ex vivo provision of CD40 and IL-21 receptor signals can drive B10-cell development and expansion by four-million-fold, and generate B10 effector cells producing IL-10 that markedly inhibit disease symptoms when transferred into mice with established autoimmune disease. The ex vivo expansion and reinfusion of autologous B10 cells may provide a novel and effective in vivo treatment for severe autoimmune diseases that are resistant to current therapies.

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  SLE is a systemic autoimmune disease characterized by overactivation of autoreactive memory B cells. However, little is known about the mechanism of qualitative abnormality of B cells. The subset classification of T cells by expression pattern of master transcription factors and chemokine receptors has been established. The biology of T cells is useful information to assess qualitative abnormality of B cells. Therefore, we focused on the expression of chemokine receptors such as CXCR5 and CXCR3 on B cells in order to define the B cell subset classification in patients with SLE. Our results revealed that pathological B cells, which lose CXCR5 and express CXCR3, might be involved in autoantibody production through the interaction with Tfh cells, and in acquisition of effector function of memory B cells during the pathological process in SLE. In addition, the results revealed that those effector B cells still remained after improvement of disease activity by immunosuppressive therapy, indicating that the quantitative abnormality, which is not improved by current therapy, may underlie in this disease.

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  Autoantibodies are associated with various autoimmune diseases. Systemic lupus erythematosus (SLE) is an autoantibody-associated autoimmune disease which affects multiple organs. Although both genetic and environmental factors are implicated in lupus pathogenesis, the etiology of the disease remains elusive. The discovery of CD4⁺CD25⁺ regulatory T cells (Tregs) that characteristically express forkhead box p3 (Foxp3) gene have greatly advanced our understanding of immune systems in autoimmune diseases. CD4⁺ Tregs can be classified into two main populations: thymus-derived naturally occurring Tregs (nTregs) and induced Tregs (iTregs) generated from CD4⁺CD25⁻ precursors in the periphery. Recently, accumulating evidence suggests that these Tregs play important roles in the regulation of humoral immune responses. In this review, we discuss recent findings on the role of Tregs in SLE.

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