Hepatic Mac2-BP expression depends on liver fibrosis and inflammation due to fat accumulation in patients with metabolic dysfunction-associated steatotic liver disease.

AIM: Data on the upregulation of Mac-2 binding protein (M2BP) expression associated with fat accumulation in the liver are limited. Therefore, we aimed to assess the relationship between hepatic M2BP expression and changes in the liver microenvironment due to fat accumulation in patients with metabolic dysfunction associated steatotic liver disease (MASLD). METHODS: Liver specimens obtained from 46 patients with MASLD were subjected to immunohistochemical staining to visualize M2BP expression in the liver. The staining intensity in the hepatocytes and sinusoidal cells was classified as high or low grade. First, the correlation between hepatic M2BP expression and microenvironmental changes caused by fat accumulation was examined. Then, the influence of hepatic M2BP expression on serum M2BP glycosylation isomer levels in patients with MASLD was evaluated. RESULTS: The staining grade of M2BP was higher in the sinusoidal cells than in the hepatocytes (p = 0.015). The patients with high staining grade in their hepatocytes had more severe lobular inflammation than those with low staining grade (p = 0.037). Additionally, the patients with high staining grade in their sinusoidal cells presented more severe fibrosis than those with low staining grade (p = 0.018). The staining grade in the hepatocytes correlated positively with serum M2BP glycosylation isomer levels (p = 0.023), whereas no correlation was observed between sinusoidal staining grade and serum M2BP glycosylation isomer levels (p = 0.393). CONCLUSIONS: Fat accumulation in patients with MASLD leads to M2BP expression in hepatocytes due to liver inflammation and that in sinusoidal cells due to fibrosis.

Establishment of an in-vitro inflammatory bowel disease model using immunological differentiation of Caco-2 cells.

Studies on intestinal cell differentiation, particularly in dextran sodium sulfate (DSS)-induced inflammatory bowel disease (IBD), have predominantly focused on the disruption of intestinal crypts and suppressive effects on the intestinal microbiota; however, repeated administration of DSS is required to induce inflammatory pathology, and there is a lack of observation of early responses and consideration of differentiation stages. Although colonic adenocarcinoma (Caco-2) cells can be used as intestinal cell models, research on these cells in an immature state is limited. We, therefore, investigated the relationship between Caco-2 cell culture duration and immunological differentiation using α-defensin5 (DEFA5) as an indicator of intestinal immunity and differentiation. Changes in protein and gene expression levels in response to DSS were examined at each differentiation stage. Expression of immune- and differentiation-related proteins, including DEFA5 and lysozyme, was evident from Day 8 of culture. Immune responses to DSS varied with the differentiation stage, affecting cell viability and cytokine expression.•Caco-2 cell culture duration correlates with the differentiation stage of Paneth cells.•DSS exposure elicits different effects depending on the differentiation stage.•Our in-vitro model of IBD facilitates the characterization of the cell differentiation process and provides a methodology to help elucidate the causal mechanisms of IBD.

Recent progress of Stevens-Johnson syndrome/toxic epidermal necrolysis: Diagnosis criteria, pathogenesis and therapy.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) represent a severe spectrum of rare mucocutaneous reactions, primarily drug-induced and characterized by significant morbidity and mortality. These conditions manifest through extensive skin detachment, distinguishing them from other generalized skin eruptions. The rarity and severity of SJS/TEN underscore the importance of accurate diagnostic criteria and effective treatments, which are currently lacking consensus. This review proposes new diagnostic criteria to improve specificity and global applicability. Recent advancements in understanding the immunopathogenesis of SJS/TEN are explored, emphasizing the role of drug-specific T cell responses and HLA polymorphisms in disease onset. The review also addresses current therapeutic approaches, including controversies surrounding the use of immunosuppressive agents and the emerging role of TNF-α inhibitors. Novel therapeutic strategies targeting specific pathogenic mechanisms, such as necroptosis and specific immune cell pathways, are discussed. Furthermore, the development of new drugs based on these insights, including targeted monoclonal antibodies and inhibitors, are examined. The review concludes by advocating for more robust and coordinated efforts across multidisciplinary medical fields to develop effective treatments and diagnostic tools for SJS/TEN, with the aim of improving patient outcomes and understanding of the disease and its mechanisms.

Complete Match of Streptococcus salivarius from Oral Saliva and Stool in a Patient with Hepatic Encephalopathy.

We herein report a 67-year-old Japanese woman with liver cirrhosis caused by primary biliary cholangitis. The patient was admitted to the hospital with loss of consciousness. Hepatic encephalopathy (HE) was diagnosed after diagnostic imaging and symptom assessments. Molecular biology tests were performed on oral saliva and stool samples. The test results indicated sequence similarity between urease-positive S. salivarius in both oral saliva and stool, as revealed by the signals in the overlapping peaks. This bacterium can potentially increase ammonia production in the gut, leading to HE in patients with liver cirrhosis.

Identification and Evaluation of Reversible Covalent Binders to Cys55 of Bfl-1 from a DNA-Encoded Chemical Library Screen.

Bfl-1 is overexpressed in both hematological and solid tumors; therefore, inhibitors of Bfl-1 are highly desirable. A DNA-encoded chemical library (DEL) screen against Bfl-1 identified the first known reversible covalent small-molecule ligand for Bfl-1. The binding was validated through biophysical and biochemical techniques, which confirmed the reversible covalent mechanism of action and pointed to binding through Cys55. This represented the first identification of a cyano-acrylamide reversible covalent compound from a DEL screen and highlights further opportunities for covalent drug discovery through DEL screening. A 10-fold improvement in potency was achieved through a systematic SAR exploration of the hit. The more potent analogue compound 13 was successfully cocrystallized in Bfl-1, revealing the binding mode and providing further evidence of a covalent interaction with Cys55.

CD14+ Dendritic-Shaped Cells Functioning as Dendritic Cells in Rheumatoid Arthritis Synovial Tissues.

OBJECTIVE: We previously reported that CD14+ dendritic-shaped cells exhibit a dendritic morphology, engage in pseudo-emperipolesis with lymphocytes, and express CD90 in the perivascular areas of rheumatoid arthritis (RA) synovial tissues. However, it remains unclear whether these CD14highCD90intermediate(int) cells function as dendritic cells. In this study, we investigated the dendritic cell-differentiation potential of CD14highCD90int cells. METHODS: The localization and number of CD14highCD90int cells in RA synovial tissues and peripheral blood were examined. The dendritic cell-differentiation potential of CD14highCD90int cells was examined by measuring interleukin-6 and tumor necrosis factor-α levels in the supernatant and CD83 and human leukocyte antigen (HLA)-DR expression in the cells after induction of dendritic cell differentiation. Synovial cells were co-cultured with lymphocytes, and the activation of these cells was examined. RESULTS: CD14highCD90int cells were abundant in RA synovial tissues, including the sublining layer and the pannus areas. Patients with untreated and active RA had significantly higher percentages of CD14highCD90int cells in the peripheral blood and synovial tissues. In RA synovial cells, inflammatory cytokine levels increased with dendritic cell-differentiation culture, but CD83 and HLA-DR expression were significantly increased in the CD14highCD90int cell group. When co-cultured with lymphocytes, cell numbers and inflammatory cytokine levels significantly increased in both groups of synovial cells after dendritic cell induction. CONCLUSION: CD14+ cells migrate and spread from the circulating blood to RA synovial tissues while expressing CD90, and CD14highCD90int cells in contact with lymphocytes differentiate into HLA-DR+ dendritic cells, which contribute to chronic inflammation in RA.

Curcumin effects on age-related changes in oral immunity: an in vivo study.

The current study aimed to investigate the effects of ageing on oral immunity using ß-defensin (DEFB) 1/2 as a marker and evaluate the effects of curcumin (CUR) on these processes. The study sample included thirty male C57BL/6J mice divided into three groups based on the treatment method used. The young control (YC) and old control (OC) groups received 0·5 % methylcellulose-400 (CUR vehicle) orally for 5 days, whereas the CUR group of older mice received a CUR solution suspended in 0·5 % methylcellulose-400 (dose: 3·0 mg/kg body). DEFB1/2 and immune indicator levels were measured in the saliva and salivary glands post-treatment. The saliva volume and protein content were significantly reduced in the OC group compared with the YC group. CUR administration restored these parameters, decreased DEFB1 expression in the salivary gland and increased DEFB1/2 secretion and DEFB2 expression. These findings were supported by epigenetic gene regulation and partial cytokine activation from changes in WD40 repeat protein 5, TNF alpha and IL-1beta. CUR can partially restore age-related changes in oral immune responses and promote oral health, thereby preventing frailty in the older population through a nutritional therapeutic pathway.

Inhibitors of the Thioesterase Activity of Mycobacterium tuberculosis Pks13 Discovered Using DNA-Encoded Chemical Library Screening.

DNA-encoded chemical library (DEL) technology provides a time- and cost-efficient method to simultaneously screen billions of compounds for their affinity to a protein target of interest. Here we report its use to identify a novel chemical series of inhibitors of the thioesterase activity of polyketide synthase 13 (Pks13) from Mycobacterium tuberculosis (Mtb). We present three chemically distinct series of inhibitors along with their enzymatic and Mtb whole cell potency, the measure of on-target activity in cells, and the crystal structures of inhibitor-enzyme complexes illuminating their interactions with the active site of the enzyme. One of these inhibitors showed a favorable pharmacokinetic profile and demonstrated efficacy in an acute mouse model of tuberculosis (TB) infection. These findings and assay developments will aid in the advancement of TB drug discovery.

IL-33 Reduces Saturated Fatty Acid Accumulation in Mouse Atherosclerotic Foci.

The cellular and molecular mechanisms of atherosclerosis are still unclear. Type 2 innate lymphocytes (ILC2) exhibit anti-inflammatory properties and protect against atherosclerosis. This study aimed to elucidate the pathogenesis of atherosclerosis development using atherosclerosis model mice (ApoE KO mice) and mice deficient in IL-33 receptor ST2 (ApoEST2 DKO mice). Sixteen-week-old male ApoE KO and ApoEST2 DKO mice were subjected to an 8-week regimen of a high-fat, high-sucrose diet. Atherosclerotic foci were assessed histologically at the aortic valve ring. Chronic inflammation was assessed using flow cytometry and real-time polymerase chain reaction. In addition, saturated fatty acids (palmitic acid) and IL-33 were administered to human aortic endothelial cells (HAECs) to assess fatty acid metabolism. ApoEST2 DKO mice with attenuated ILC2 had significantly worse atherosclerosis than ApoE KO mice. The levels of saturated fatty acids, including palmitic acid, were significantly elevated in the arteries and serum of ApoEST2 DKO mice. Furthermore, on treating HAECs with saturated fatty acids with or without IL-33, the Oil Red O staining area significantly decreased in the IL-33-treated group compared to that in the non-treated group. IL-33 potentially prevented the accumulation of saturated fatty acids within atherosclerotic foci.

Regulation of Chloride Channels by Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor-Induced α-Defensin 5.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are used to treat non-small cell lung cancer with EGFR mutations. However, first-generation erlotinib and second-generation afatinib often cause diarrhea, which may develop because of the association between EGFR-TKIs and the chloride channel or abnormalities in the intestinal microbiota due to disruption of the intestinal immune system. As reports on the effects of EGFR-TKIs on intestinal immunity are lacking, we aimed to determine whether the intestinal immune system is involved in the molecular effects of EGFR-TKIs on chloride channels using Caco-2 cells. Initially, we evaluated the association of chloride channels with α-defensin 5 (DEFA5), a marker of intestinal immunity. Erlotinib and afatinib significantly increased the extracellularly secreted DEFA5 level and autophagy-related 16-like 1 and X-box binding protein 1 transcript levels, indicative of enhanced granule exocytosis. Conversely, intracellular DEFA5 and Toll-like receptor 4 protein expression and tumor necrosis factor-α transcript levels decreased significantly, suggesting that Toll-like receptor 4 suppression repressed DEFA5 production. Furthermore, among the chloride channels, DEFA5 was found to significantly increase the transcript levels of cystic fibrosis transmembrane conductance regulators. These results indicate that DEFA5 plays a significant role in the mechanism of chloride channel-mediated diarrhea induced by EGFR-TKIs. Therefore, we successfully elucidated the potential host action of DEFA5 in cancer therapy for the first time.

Metabolic Dysfunction-Associated Fatty Liver Disease on Distinct Microbial Communities at the Bacterial Phylum Level.

INTRODUCTION: Limited data are available on the correlation between microbial communities and metabolic dysfunction-associated fatty liver disease (MAFLD). This study aimed to evaluate the influence of MAFLD on diverse microbial communities. METHODS: We recruited 43 patients with a nonviral liver disease. Enrolled patients were divided into two groups according to MAFLD criteria. The fecal microbial composition was evaluated using the variable V3-V4 region of the 16S ribosomal RNA region, which was amplified using polymerase chain reaction. First, we assessed the influence of MAFLD on distinct microbial communities at the bacterial phylum level. Next, the correlation between the microbial communities and diversity in patients with MAFLD was evaluated. RESULTS: Among the enrolled participants, the non-MAFLD and MAFLD groups consisted of 21 and 22 patients, respectively. Sequences were distributed among ten bacterial phyla. The relative abundance of Firmicutes was significantly higher in the MAFLD group than in the non-MAFLD group (p = 0.014). The microbial diversity was not significantly influenced by the presence of MAFLD (Chao-1 index: p = 0.215 and Shannon index: p = 0.174, respectively); nonetheless, the correlation coefficient between the abundances of Firmicutes and microbial diversity was higher in the non-MAFLD group than in the MAFLD group. CONCLUSION: The presence of MAFLD increased the relative abundances of Firmicutes at the bacterial phylum level, which may cause the discrepancy between the abundances of Firmicutes and diversity in patients with MAFLD.

Role of the NLRP1 inflammasome in skin cancer and inflammatory skin diseases.

Inflammasomes are cytoplasmic protein complexes that play a crucial role in protecting the host against pathogenic and sterile stressors by initiating inflammation. Upon activation, these complexes directly regulate the proteolytic processing and activation of proinflammatory cytokines interleukin (IL)-1ß and IL-18 to induce a potent inflammatory response, and induce a programmed form of cell death called pyroptosis to expose intracellular pathogens to the surveillance of the immune system, thus perpetuating inflammation. There are various types of inflammasome complexes, with the NLRP1 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-1) inflammasome being the first one identified and currently recognized as the predominant inflammasome sensor protein in human keratinocytes. Human NLRP1 exhibits a unique domain structure, containing both an N-terminal pyrin (PYD) domain and an effector C-terminal caspase recruitment domain (CARD). It can be activated by diverse stimuli, such as viruses, ultraviolet B radiation and ribotoxic stress responses. Specific mutations in NLRP1 or related genes have been associated with rare monogenic skin disorders, such as multiple self-healing palmoplantar carcinoma; familial keratosis lichenoides chronica; autoinflammation with arthritis and dyskeratosis; and dipeptidyl peptidase 9 deficiency. Recent research breakthroughs have also highlighted the involvement of dysfunctions in the NLRP1 pathway in a handful of seemingly unrelated dermatological conditions. These range from monogenic autoinflammatory diseases to polygenic autoimmune diseases such as vitiligo, psoriasis, atopic dermatitis and skin cancer, including squamous cell carcinoma, melanoma and Kaposi sarcoma. Additionally, emerging evidence implicates NLRP1 in systemic lupus erythematosus, pemphigus vulgaris, Addison disease, Papillon-Lefèvre syndrome and leprosy. The aim of this review is to shed light on the implications of pathological dysregulation of the NLRP1 inflammasome in skin diseases and investigate the potential rationale for targeting this pathway as a future therapeutic approach.

Genetic mutations in pyoderma gangrenosum, hidradenitis suppurativa, and associated autoinflammatory syndromes: Insights into pathogenic mechanisms and shared pathways.

Pyoderma gangrenosum (PG), hidradenitis suppurativa (HS), and the associated autoinflammatory syndromes, including pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome, PSTPIP1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome, pyoderma gangrenosum, acne, and hidradenitis suppurativa (PASH) syndrome, and pyogenic arthritis, pyoderma gangrenosum, acne, and suppurative hidradenitis (PAPASH) syndrome are dermatological conditions characterized by chronic inflammation and tissue damage. Recent advances in genetic research have identified specific mutations associated with these disorders, shedding light on their underlying pathogenic mechanisms. This review aims to summarize the current knowledge of identified mutations and presumed pathophysiology in PG, HS, and the associated autoinflammatory syndromes.

Immune checkpoint inhibitor-induced epidermal necrolysis: A narrative review evaluating demographics, clinical features, and culprit medications.

Immune checkpoint inhibitors (ICIs) have transformed cancer treatment but can cause immune-related adverse events (irAEs). Severe cutaneous irAEs, including epidermal necrolysis, are rare but potentially life-threatening. There is limited understanding of the clinical features and management of ICI-induced Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), so we aimed to analyze 95 cases of ICI-induced SJS/TEN (35 cases of SJS, 26 cases of TEN, two cases of SJS/TEN overlap, and 32 cases of unspecified) to increase knowledge of this condition among oncologists and dermatologists. We conducted a comprehensive search of PubMed for all relevant case reports published until the end of December 2022, and collected data on patient demographics, cancer type, ICI regimen, time to onset of SJS/TEN, clinical presentation, management strategies, and outcomes. PD-1 inhibitors were the most common ICIs associated with SJS/TEN (58.9%), followed by the combination of PD-1 and CTLA-4 inhibitors (11.6%), and PD-L1 inhibitors (6.3%). Lung cancer and melanoma were the most frequent malignancies treated (35.8% and 25.4%, respectively). SJS/TEN occurred most frequently within the first 4 weeks (51.7%), and corticosteroid monotherapy was the most commonly chosen systemic treatment (56.4%). The overall mortality rate of ICI-induced SJS/TEN was 30.8%. Our findings highlight the frequency and severity of ICI-induced SJS/TEN and the urgent need for predictive molecular biomarkers aimed at preventive measures and early intervention.

Regnase-1 downregulation promotes pancreatic cancer through myeloid-derived suppressor cell-mediated evasion of anticancer immunity.

BACKGROUND: Pancreatitis is known to be an important risk factor for pancreatic ductal adenocarcinoma (PDAC). However, the exact molecular mechanisms of how inflammation promotes PDAC are still not fully understood. Regnase-1, an endoribonuclease, regulates immune responses by degrading mRNAs of inflammation-related genes. Herein, we investigated the role of Regnase-1 in PDAC. METHODS: Clinical significance of intratumor Regnase-1 expression was evaluated by immunohistochemistry in 39 surgically-resected PDAC patients. The functional role of Regnase-1 was investigated by pancreas-specific Regnase-1 knockout mice and Kras-mutant Regnase-1 knockout mice. The mechanistic studies with gene silencing, RNA immunoprecipitation sequencing (RIP-seq) and immune cell reconstitution were performed in human/mouse PDAC cell lines and a syngeneic orthotopic tumor transplantation model of KrasG12D-mutant and Trp53-deficient PDAC cells. RESULTS: Regnase-1 expression was negatively correlated with the clinical outcomes and an independent predictor of poor relapse-free and overall survival in PDAC patients. Pancreas-specific Regnase-1 deletion in mice promoteed pancreatic cancer with PMN-MDSC infiltration and shortened their survival. A syngeneic orthotopic PDAC model exhibited that Regnase-1 downregulation accelerated tumor progression via recruitment of intratumor CD11b+ MDSCs. Mechanistically, Regnase-1 directly negatively regulated a variety of chemokines/cytokines important for MDSC recruitment and activation, including CXCL1, CXCL2, CSF2, and TGFß, in pancreatic cancer cells. We subsequently showed that IL-1ß-mediated Regnase-1 downregulation recruited MDSCs to tumor sites and promoted pancreatic cancer progression via mitigation of cytotoxic T lympohocytes-mediated antitumor immunity. CONCLUSIONS: IL-1b-mediated Regnase-1 downregulation induces MDSCs and promotes pancreatic cancer through the evasion of anticancer immunity.

Characterisation of IL-1 family members in Sweet syndrome highlights the overexpression of IL-1ß and IL-1R3 as possible therapeutic targets.

Sweet syndrome (SS) as a prototypic neutrophilic dermatosis (NDs) shares certain clinical and histologic features with monogenic auto-inflammatory disorders in which interleukin (IL)-1 cytokine family members play an important role. This has led to the proposal that NDs are polygenic auto-inflammatory diseases and has fuelled research to further understand the role of IL-1 family members in the pathogenesis of NDs. The aim of this study was to characterise the expression of the IL-1 family members IL-1ß, IL-36γ, IL-33 and IL-1R3 (IL-1RaP) in SS. The expression profile of IL-1ß, IL-33, IL-36γ and their common co-receptor IL-1R3 was analysed by immunohistochemistry, in situ hybridisation and double immunofluorescence (IF) in healthy control skin (HC) and lesional skin samples of SS. Marked overexpression of IL-1ß in the dermis of SS (p < 0.001), and a non-significant increase in dermal (p = 0.087) and epidermal (p = 0.345) IL-36γ expression compared to HC was observed. Significantly increased IL-1R3 expression within the dermal infiltrate of SS skin samples (p = 0.02) was also observed, whereas no difference in IL-33 expression was found between SS and HC (p = 0.7139). In situ hybridisation revealed a good correlation between gene expression levels and the above protein expression levels. Double IF identifies neutrophils and macrophages as the predominant sources of IL-1ß. This study shows that IL-1ß produced by macrophages and neutrophils and IL-1R3 are significantly overexpressed in SS, thereby indicating a potential pathogenic role for this cytokine and receptor in SS.

[Functional diversity of disorder-specific macrophage subtype].

Macrophages have been discovered more than 100 years ago. Recent studies indicated that monocytes and macrophages can be categorized into several distinct phenotypes and their respective differentiation mechanisms are known. We also reported that the Jmjd3 is critical for the macrophage subtype activated by allergic stimuli and that the tissue resident macrophage subtype in adipose tissue, which is controlled by Trib1, is responsible for maintaining homeostasis of peripheral tissues such as adipocyte. Thus, it is considered that various macrophage/monocyte subtypes corresponding to certain disorders were existed in our body. Furthermore, in order to investigate the relationship between macrophage subtype and disease, we focused on fibrosis as the next target disease. Its pathogenesis is poorly understood, and there are few effective therapies. Previously we found that a new macrophage/monocyte subtype, which their markers are Msr1+Ceacam1+Ly6C-Mac1+F4/80-monocyte and share granulocyte characteristics, involved in development of fibrosis was accumulated in the affected area in the lungs at the beginning of fibrosis. We termed the monocyte/ macrophage subtype segregated-nucleus-containing atypical monocytes (SatM). Towards understanding the mechanism of fibrosis onset, we next focused on investigation of non-haematopoietic cells involved in activation of immune cell such as SatM during fibrotic phase.

Expression of the readthrough transcript CiDRE in alveolar macrophages boosts SARS-CoV-2 susceptibility and promotes COVID-19 severity.

Lung infection during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via the angiotensin-I-converting enzyme 2 (ACE2) receptor induces a cytokine storm. However, the precise mechanisms involved in severe COVID-19 pneumonia are unknown. Here, we showed that interleukin-10 (IL-10) induced the expression of ACE2 in normal alveolar macrophages, causing them to become vectors for SARS-CoV-2. The inhibition of this system in hamster models attenuated SARS-CoV-2 pathogenicity. Genome-wide association and quantitative trait locus analyses identified a IFNAR2-IL10RB readthrough transcript, COVID-19 infectivity-enhancing dual receptor (CiDRE), which was highly expressed in patients harboring COVID-19 risk variants at the IFNAR2 locus. We showed that CiDRE exerted synergistic effects via the IL-10-ACE2 axis in alveolar macrophages and functioned as a decoy receptor for type I interferons. Collectively, our data show that high IL-10 and CiDRE expression are potential risk factors for severe COVID-19. Thus, IL-10R and CiDRE inhibitors might be useful COVID-19 therapies.

Divergent in situ expression of IL-31 and IL-31RA between bullous pemphigoid and pemphigus vulgaris.

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are two major autoimmune blistering skin diseases. Unlike PV, BP is accompanied by intense pruritus, suggesting possible involvement of the pruritogenic cytokine IL-31. However, the underlying mechanisms of the clinical difference between BP and PV in terms of pruritus are not fully understood. To compare the expression levels of IL-31 and its receptor IL-31RA in the lesional skin, including peripheral nerves in BP and PV patients, immunohistochemical staining for IL-31 and IL-31RA was performed in skin samples of BP and PV patients and healthy controls (HC). The IL-31RA-expressing area in epidermis and peripheral nerves was analysed using ImageJ and the percentage of positive cells for IL-31/IL-31RA in dermal infiltrating cells was manually quantified. Quantitative analyses revealed that IL-31/IL-31RA expressions in the epidermis and dermal infiltrate were significantly increased in BP compared to PV and HC. The difference between BP and PV became more obvious when advanced bullous lesions were compared. Peripheral nerves in BP lesions presented significantly higher IL-31RA expression compared to PV lesions. In conclusion, we found significantly augmented expressions of IL-31/IL-31RA in BP lesions, including peripheral nerves, in comparison to PV. These results suggest a possible contribution of IL-31/IL-31RA signalling to the difference between BP and PV in the facilitation of pruritus and local skin inflammation, raising the possibility of therapeutic targeting of the IL-31/IL-31RA pathway in BP patients.