Desmoglein-Specific B-Cell-Targeted Single-Cell Analysis Revealing Unique Gene Regulation in Patients with Pemphigus.

Autoreactive B cells are assumed to play a critical role in pemphigus; however, the characteristics of these cells are not yet fully understood. In this study, 23 pemphigus vulgaris or pemphigus foliaceus samples were used to isolate circulating desmoglein (DSG)-specific B cells. Transcriptome analysis of the samples was performed at the single-cell level to detect genes involved in disease activity. DSG1- or DSG3-specific B cells from three patients' differentially expressed genes related to T cell costimulation (CD137L) as well as B-cell differentiation (CD9, BATF, TIMP1) and inflammation (S100A8, S100A9, CCR3), compared with nonspecific B cells from the same patients. When the DSG1-specific B cells before and after treatment transcriptomes of the patient with pemphigus foliaceus were compared, there were changes in several B-cell activation pathways not detected in non-DSG1-specific B cells. This study clarifies the transcriptomic profile of autoreactive B cells in patients with pemphigus and documents the gene expression related to disease activity. Our approach can be applied to other autoimmune diseases and has the potential for future detection of disease-specific autoimmune cells.

IgM to IgG Class Switching Is a Necessary Step for Pemphigus Phenotype Induction in Desmoglein 3-Specific B Cell Receptor Knock-in Mouse.

Pemphigus vulgaris is an autoimmune blistering disease caused by IgG targeting desmoglein 3 (Dsg3), an adhesion molecule of keratinocytes. Anti-Dsg3 IgG production is prevented in healthy individuals, but it is unclear how Dsg3-specific B cells are regulated. To clarify the immunological condition regulating Dsg3-specific B cells, a pathogenic anti-Dsg3 Ig (AK23) knock-in mouse was generated. AK23 knock-in B cells developed normally without undergoing deletion or acquiring an anergic phenotype in vivo. The knock-in B cells showed Ca2+ influx upon IgM cross-linking and differentiated into AK23-IgG+ B cells after LPS and IL-4 stimulation in vitro that induced a pemphigus phenotype after adoptive transfer into Rag2 -/- mice. However, the knock-in mouse itself produced AK23-IgM but little IgG without blisters in vivo. Dsg3 immunization and skin inflammation caused AK23-IgG production and a pemphigus phenotype in vivo. Furthermore, Fcgr2b deficiency or haploinsufficiency spontaneously induced AK23-IgG production and a pemphigus phenotype with poor survival rates in AK23 knock-in mice. To assess Fcgr2b involvement in Ig class-switch efficiency, postswitch transcripts of B cells were quantified and significantly higher in Fcgr2b -/- and Fcgr2b +/- mice than wild-type mice in a gene dose-dependent manner. Finally, RNA sequencing revealed reduced expression of FCGR2B and FcγRIIB-related genes in patient B cells. These results indicated that Dsg3-specific B cells do not spontaneously perform pathogenic class switching in vivo, and pemphigus phenotype induction was prevented under normal conditions. Attenuated FcγRIIB signaling is also one of the drivers for pathogenic class switching and is consistent with immunological features identified from clinical samples. This study unveiled a characteristic immune state silencing autoreactive B cells in mice.

Peripheral tolerance by Treg via constraining OX40 signal in autoreactive T cells against desmoglein 3, a target antigen in pemphigus.

Antigen-specific peripheral tolerance is crucial to prevent the development of organ-specific autoimmunity. However, its function decoupled from thymic tolerance remains unclear. We used desmoglein 3 (Dsg3), a pemphigus antigen expressed in keratinocytes, to analyze peripheral tolerance under physiological antigen-expression conditions. Dsg3-deficient thymi were transplanted into athymic mice to create a unique condition in which Dsg3 was expressed only in peripheral tissue but not in the thymus. When bone marrow transfer was conducted from high-avidity Dsg3-specific T cell receptor-transgenic mice to thymus-transplanted mice, Dsg3-specific CD4+ T cells developed in the transplanted thymus but subsequently disappeared in the periphery. Additionally, when Dsg3-specific T cells developed in Dsg3-/- mice were adoptively transferred into Dsg3-sufficient recipients, the T cells disappeared in an antigen-specific manner without inducing autoimmune dermatitis. However, Dsg3-specific T cells overcame this disappearance and thus induced autoimmune dermatitis in Treg-ablated recipients but not in Foxp3-mutant recipients with dysfunctional Tregs. The molecules involved in disappearance were sought by screening the transcriptomes of wild-type and Foxp3-mutant Tregs. OX40 of Tregs was suggested to be responsible. Consistently, when OX40 expression of Tregs was constrained, Dsg3-specific T cells did not disappear. Furthermore, Tregs obtained OX40L from dendritic cells in an OX40-dependent manner in vitro and then suppressed OX40L expression in dendritic cells and Birc5 expression in Dsg3-specific T cells in vivo. Lastly, CRISPR/Cas9-mediated knockout of OX40 signaling in Dsg3-specific T cells restored their disappearance in Treg-ablated recipients. Thus, Treg-mediated peripheral deletion of autoreactive T cells operates as an OX40-dependent regulatory mechanism to avoid undesired autoimmunity besides thymic tolerance.

Is Local Production of Autoantibodies in Skin Lesions Relevant in Pemphigus?

Pemphigus is an autoimmune bullous disease characterized by IgG production against desmogleins. The major sites of autoantibody production are thought to be lymph nodes, spleen, and bone marrow. Previously, it has been suggested that autoreactive B cells might exist in the skin lesions in pemphigus and produce autoantibodies. In their report, Zhou et al. expanded their previous studies and reported that ectopic lymphoid-like structures were found in pemphigus skin lesions, wherein B-cell differentiation and lesional B-cell expansion might progress. This finding provides novel insights into B-cell biology in pemphigus.

Autoimmunity and immunological tolerance in autoimmune bullous diseases.

Autoimmune diseases are devastating conditions in which the immune system is directed against the host, leading to life-threatening destruction of organs. Although autoantigens are ill-defined in most autoimmune diseases, this is not the case in the skin. Autoimmune bullous diseases have been extensively studied with detailed characterization of autoantigens, the epitopes that are targeted, and the mechanisms of action that mediate autoimmune tissue destruction. Pemphigus is an autoimmune bullous disease caused by circulating IgG that targets two desmosomal proteins, desmoglein 1 and 3, which are crucial for cell-cell adhesion of keratinocytes. Binding of auto-antibodies to desmogleins impairs keratinocyte adhesion, leading to severe blistering disease. Mouse models that recapitulate the human disease have been instrumental in elucidating the detailed pathophysiology. Taking advantage of the fact that desmogleins are specifically targeted in pemphigus, studying humoral and cellular autoimmunity against these autoantigens provides us with an opportunity to understand not only the effector mechanisms of B and T cells in mediating pathology but also how autoreactive lymphocytes are regulated during development in the thymus and post-development in the periphery. This review introduces pemphigus and its subtypes as prototypic autoimmune diseases from which recent basic and translational developments should provide insight into how autoimmunity develops.

Case of lamotrigine-induced drug adverse reaction under tocilizumab treatment with clinical and virological features of drug-induced hypersensitivity syndrome.

The pathological mechanisms and immunological kinetics of drug-induced hypersensitivity syndrome (DIHS), including the relevance of interleukin (IL)-6, remain unclear. We report a case of drug adverse reaction that does not fulfill the diagnostic criteria of DIHS but mimics its characteristic features. Because the patient was under anti-IL-6 therapy at the onset, some symptoms typically seen in DIHS were absent, such as fever and leukocyte count abnormalities. However, the characteristic features of DIHS were clearly observed in the subsequent course, including the repeated recurrence of skin rash, prolonged liver dysfunction and reactivation of herpes viruses. This case suggested that IL-6 role at the onset is not a main factor to determine the subsequent pathomechanism of DIHS and attention should be paid to the preceding therapy for achieving accurate diagnosis.

[Psoriasis and Psoriatic Arthritis Induced by Nivolumab in a Patient with Advanced Non-Small-Cell Lung Cancer].

BACKGROUND: Immune checkpoint-blocking antibodies may induce specific side effects known as immune-relatedad verse events. CASE PRESENTATION: A 66-year-oldman without any history of autoimmune disease was referredto our hospital for treatment of lung cancer in the right upper lobe. The tumor was diagnosed as Stage III A non-small-cell lung cancer by using bronchoscopic biopsy, computedtomography, andFDG -PET. After a single course of cisplatin andpemetrexed , the tumor size increasedremarkably andthe regimen was changedto nivolumab(3mg/kg every 2 weeks). Psoriasis andpsoriatic arthritis were observed after 4 courses of nivolumab. Nivolumab treatment continued, and the oral administration of predni- solone(20mg/day)couldimprove psoriasis andpsoriatic arthritis. However, the lung cancer showedprogressive disease after the 11th course of nivolumab. CONCLUSION: Psoriasis andpsoriatic arthritis were inducedby nivolumab in the patient without any history of autoimmune disease. It is unclear how prednisolone affected nivolumab for the treatment of lung cancer.

Unexpected recalcitrant course of drug-induced erythema multiforme-like eruption and interstitial pneumonia sequentially occurring after nivolumab therapy.

Vemurafenib improves survival of melanoma patients. However, cutaneous side-effects commonly occur in them. Nivolumab and ipilimumab are monoclonal antibodies against programmed death 1 and cytotoxic T-lymphocyte-associated antigen 4, both of which regulate excessive T-cell activation. Although these agents induce antitumor immunity against melanoma, the modified immune condition may result in an unexpected adverse reaction which has not been observed previously. Herein, we report a case who manifested severe erythema multiforme-like eruption with mucosal involvement associated with vemurafenib following nivolumab. The patient also subsequently suffered from ipilimumab-induced interstitial pneumonia with refractory course. Such a case has never been reported. This case suggested that dermatologists should pay special attention to unexpected adverse events of these drugs, and carefully observe cutaneous and respiratory status of patients during the treatment of melanoma.

Case of Rapid Progression of Hemiatrophy on the Face: A New Clinical Entity?

A lot of diseases, including lupus profundus, morphea, lipodystrophy, and Parry-Romberg syndrome, may manifest progressive hemifacial atrophy. These diseases usually progress slowly and rapid progression of atrophy is extremely rare. We report a case of elderly-onset rapid progression of hemifacial atrophy only in three weeks. Our case did not meet variable differential diagnoses. We discuss the clinical character of the patient against the past of literature and suppose it may be a new clinical entity.

False-positive serology following intravenous immunoglobulin and plasma exchange through transfusion of fresh frozen plasma in a patient with pemphigus vulgaris.

Intravenous immunoglobulin therapy and plasma exchange through transfusion of fresh frozen plasma are therapeutic options for patients with refractory pemphigus vulgaris. Passive acquisition of various clinically important antibodies through these therapies can occur, leading to false serology and negatively affecting patients' clinical care. It is recommended that dermatologists recognize the possibility of these phenomena and interpret them appropriately. Here, we report false-positive serology following intravenous immunoglobulin therapy and plasma exchange through transfusion of fresh frozen plasma in a patient with refractory pemphigus vulgaris. We also discuss the measure for misinterpretation and unnecessary clinical intervention.

Epstein-Barr virus-associated T/natural killer-cell lymphomas in the elderly: the first consensus meeting in Kofu 2013.

From a clinicopathological conference on nine elderly patients with Epstein-Barr virus (EBV)-associated T/natural killer (NK)-cell lymphoma, we have addressed the patients' backgrounds, clinical manifestations, histopathological findings, cytogenesis, complications and prognoses. Among these elderly patients (>65 years old), seven patients had extranodal NK/T-cell lymphoma, nasal type (ENKL) with an NK-cell phenotype, and two patients had EBV(+) T-cell lymphomas or lymphoproliferative disorders (LPD) with cutaneous lesions mimicking pityriasis lichenoides et varioliformis acuta (PLEVA) or hydroa vacciniforme (HV). No patients had a previous episode of EBV-related symptoms such as infectious mononucleosis, chronic active EBV infection, HV or hypersensitivity to mosquito bites. Elderly patients with ENKL may show the centroblastoid variant. EBV(+) CD8(+) CD56(+/-) lymphocytes may be responsible for the development of PLEVA or HV-like cutaneous lesions in the elderly.