O023a / #736 Topic:AS07 - Cutaneous Lupus Late-Breaking Abstract ABSTRACT CONCURRENT SESSION 03: INNATE AND ADAPTIVE IMMUNITY IN SLE 22-05-2025 1:40 PM - 2:40 PM Lupus panniculitis (LP) is a rare manifestation of cutaneous lupus erythematosus characterized by chronic inflammation of subcutaneous white adipose tissue (SWAT). Despite its distinct clinical and histopathological features, the pathomechanisms driving LP remain poorly understood, leading to untargeted therapeutic strategies. This study aimed to elucidate the cellular and molecular mechanisms underlying LP using imaging mass cytometry (IMC) and NanoString nCounter technology to identify immune signatures and gene expression profiles associated with the disease. Biopsies from 8 LP patients and 6 healthy controls (HC) were analyzed. Cell populations and spatial interactions were assessed via IMC, while gene expression profiles were evaluated using NanoString. LP lesions demonstrated extensive leukocyte infiltration, predominantly comprising T cells (CD2+) (48%), B cells (CD20+) (14%), and macrophages (15%). T cells exhibited a cytotoxic (CD8+, Granzyme B+) and skin-homing (CLA+) phenotype, with Th1 polarization driven by type II interferon signaling. B cells displayed strong spatial interactions with naïve T cells. Antigen-presenting cells (APCs) such as dendritic cells and M1 macrophages were abundant and engaged in close interactions with cytotoxic T cells. Abundance of immune cells, particularly B cells, T cells, and cytotoxic cells, in LP was confirmed at mRNA level. LP exhibited significant activation of adaptive immune pathways, with upregulation of T and B-cell signaling genes (CD3D, CD8A, CD19) and antigen presentation pathways (MHC class I and II). A Th1-dominant profile, driven by interferon signaling (STAT1, IRF7) and cytotoxic pathways (TRAIL, TNFRSF1B). Innate immunity in LP showed significant upregulation of Toll-like receptor (TLR) signaling genes (TLR1, TLR2, MYD88). Immunometabolism pathways were altered, with upregulation of IDO1, a key enzyme in tryptophan metabolism, while AHR was downregulated. Complement pathways were activated with upregulation of classical components (C1QA, C1QB) and other regulatory changes. This study highlights the role of cytotoxic and skin-homing T- and B cell-predominated immune response and complement activation and immunometabolic dysregulation is involved in LP. The findings provide valuable insights into cellular interactions and gene expression profiles, suggesting potential therapeutic targets, including interferon inhibitors, complement regulators, and metabolic modulators, to improve LP management.

Immune checkpoint inhibitor (ICI) treatment for metastasized melanoma is often associated with immune-related adverse events, one of them being vitiligo-like depigmentation (VLD). Classical vitiligo is an autoimmune disease considered to result from a cytotoxic response of resident memory T-cells against melanocytes. However, the pathomechanisms underlying the development of VLD are poorly understood. In this study, we wanted to investigate and explore the cellular and molecular signatures of VLD and classical vitiligo to gain insights into pathomechanistic features of the two diseases. We collected lesional and non-lesional skin biopsies from 8 VLD patients receiving ICI for metastasized melanoma and 8 classical vitiligo patients. In addition, we collected 8 healthy control (HC) skin samples. All tissue specimens were processed using spatial whole transcriptomics of regions of T cell infiltration. Differential gene expression and enrichment analysis revealed distinct molecular profiles of VLD, vitiligo and HC. In VLD, there was an overexpression of genes associated with activation of the MHC class II protein complex (the HLA class II alpha/beta chain, CD74), which is critical for antigen presentation to CD4+ T lymphocytes. Comparative enrichment analysis between VLD and vitiligo showed more significant activation of genes related to peptide antigen processing and presentation by MHC I, as well as signs of B cell activation (e.g., CD81 and IGHG2/4) in vitiligo. On the other hand, genes related to epidermal cells and keratinocytes differentiation/development (e.g., CDH3, FLG, IRF6, LIPM, KRT) were significantly upregulated in VLD compared to vitiligo. In conclusion, our spatial transcriptomics analyses so far show distinct expression of antigen presentation- and T cell-related genes in VLD vs. vitiligo. We will further map antigen presenting cells and T cell subtypes, to better understand the immune axis in VLD.

Vitiligo-like depigmentation (VLD) is an immune-related adverse event (irAE) of checkpoint-inhibitor (CPI) treatment, which has previously been associated with a favourable outcome. The aim of this study was to explore clinical, biological and prognostic features of melanoma patients with VLD under CPI-treatment and to explore whether they exhibit a characteristic immune response profile in peripheral blood. Melanoma patients developing VLD under CPI were included in a prospective observational single-center cohort study. We collected and analysed clinical parameters, photographs and serum from 28 VLD patients. They received pembrolizumab (36%), nivolumab (11%), ipilimumab/nivolumab (32%) or clinical trial medications (21%). We performed a high-throughput proteomics assay (Olink), in which we identified a distinct proteomic signature in VLD patients in comparison to non-VLD CPI patients. Our clinical assessments revealed that VLD lesions had a predominantly symmetrical distribution pattern, with mostly smaller "freckle-like" macules and a preferential distribution in UV-exposed areas. Patients with previous targeted therapy showed a significantly longer time lapse between CPI initiation and VLD onset compared to non-pre-treated patients (12.5 vs. 6.25 months). Therapy responders exhibited a distinct proteomic profile when compared with non-responders in VLD such as upregulation of EDAR and downregulation of LAG3. ITGA11 was elevated in the VLD-group when compared to non-VLD-CPI-treated melanoma patients. Our findings demonstrate that on a proteomic level, VLD is characterized by a distinct immune signature when compared to CPI-treated patients without VLD and that therapy responsiveness is reflected by a characteristic immune profile. The pathomechanisms underlying these findings and how they could relate to the antitumoral response in melanoma remain to be elucidated.

BackgroundLong-term sequelae are frequent and often disabling after epidermal necrolysis (Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN)). However, consensus on the modalities of management of these sequelae is lacking.ObjectivesWe conducted an international multicentric DELPHI exercise to establish a multidisciplinary expert consensus to standardize recommendations regarding management of SJS/TEN sequelae.MethodsParticipants were sent a survey via the online tool "Survey Monkey" consisting of 54 statements organized into 8 topics: general recommendations, professionals involved, skin, oral mucosa and teeth, eyes, genital area, mental health, and allergy workup. Participants evaluated the level of appropriateness of each statement on a scale of 1 (extremely inappropriate) to 9 (extremely appropriate). Results were analyzed according to the RAND/UCLA Appropriateness Method.ResultsFifty-two healthcare professionals participated. After the first round, a consensus was obtained for 100% of 54 initially proposed statements (disagreement index < 1). Among them, 50 statements were agreed upon as 'appropriate'; four statements were considered 'uncertain', and ultimately finally discarded.ConclusionsOur DELPHI-based expert consensus should help guide physicians in conducting a prolonged multidisciplinary follow-up of sequelae in SJS-TEN.

The recognition of the unpredictable latent phase before frequent progression of melanoma is a real unmet need in melanoma care. Approximately 50% of melanoma-related deaths were early stage at the moment of diagnosis. There are no novel biomarkers with prognostic values at the early identification of the advanced melanoma attributes, therefore, we investigated the main driver mechanisms of the progression of early-stage melanomas. We analyzed a cohort of 12 primary melanomas with < Breslow level 1.6 mm divided into recurrent and non-recurrent within five years after surgical intervention. Tumor and stromal compartments in each tissue section were isolated and collected using laser-capture microdissection and submitted to quantitative proteomics. In the progression group of melanomas, the mitochondrial translation, especially 39S ribosomal proteins were upregulated in tumor cells (p<0.05). On the contrary, proteins from immune system response were downregulated (p<0.05). Interestingly, when analyzing the stromal components, a similar pattern was observed. These results shed light on the not well-understood tumor-stroma interaction, revealing a possible phenotype transferring from cancer cells to their microenvironment. In summary, by separating tumor and stromal components, our results added an additional layer of information to enrich our analysis. We have identified proteins and pathways which have key roles in molecular mechanisms of melanoma progression. The bioinformatics analysis highlighted that mitochondrial functions might play a role in melanoma pathogenesis.

Abstract Panniculitis, characterized by inflammation of the subcutaneous adipose tissue, displays diverse clinical and dermatohistopathological phenotypes. However, the underlying pathomechanisms remain largely unknown, with limited studies pointing to a delayed-type III/IV hypersensitivity reaction. In the present study, we aimed to gain new insights into the pathogenesis of the two most common panniculitis subtypes, erythema nodosum (EN) and erythema induratum (EI), by exploring their cellular and molecular immune patterns. We analyzed deep lesional skin biopsies from EN and EI patients (n=16 per group) and healthy controls (n=6) using imaging mass cytometry (IMC) to map the leukocytic infiltrate. The IMC analysis revealed distinct cellular profiles for EN and EI. In both conditions, macrophages were the predominant immune cell type, exhibiting a shift towards an M1 phenotype compared to healthy controls. In EI, the M1 macrophages were particularly prominent and were noted to cluster with activated CD8+ T cells. Conversely, EN showed fewer inflammatory features and a larger B cell population. These cellular changes were supported by an overall strong type 1 immune signature on the mRNA level in both EN and EI. This was evidenced by the upregulation of NLR-, NFkB-, and inflammasome-signaling-pathway genes compared to healthy controls. The type 1 signature was more pronounced in EI than in EN. These findings challenge the current understanding of panniculitis. They point towards a key role of M1 macrophages in mediating both innate and adaptive immune responses in panniculitis.

Immune checkpoint inhibitor (ICI) therapy has emerged as a pivotal treatment for metastatic melanoma, yet it often leads to immune-related adverse events, including vitiligo-like depigmentation (VLD). While classical vitiligo is known to stem from an autoimmune response involving cytotoxic memory T-cells targeting melanocytes, the precise mechanisms behind VLD development remain elusive. This study aims to elucidate the cellular and molecular characteristics of both VLD and classical vitiligo, shedding light on the pathomechanisms underlying these conditions. We conducted skin biopsies on both affected and unaffected areas from eight VLD patients undergoing ICI therapy for metastatic melanoma, as well as eight classical vitiligo patients. Additionally, skin samples from eight healthy control (HC) individuals were collected. We employed spatial whole transcriptomics on tissue specimens, with a particular focus on regions displaying T cell infiltration. Differential gene expression and enrichment analyses unveiled distinct molecular profiles for VLD, vitiligo, and HC. In VLD, we observed upregulation of genes associated with the activation of the MHC class II protein complex, including HLA class II alpha/beta chain and CD74, pivotal for antigen presentation to CD4+ T lymphocytes. Conversely, vitiligo skin exhibited a more pronounced activation of genes related to peptide antigen processing and presentation by MHC I, in conjunction with B cell activation genes such as CD81 and IGHG2/4. Notably, genes associated with keratinocyte differentiation and development (e.g., CDH3, FLG, IRF6, LIPM, KRT) exhibited significant upregulation in VLD when compared to vitiligo. In summary, our spatial transcriptomics analyses elucidate distinct expression patterns of genes related to antigen presentation and T cell activity in VLD compared to vitiligo. Our future research endeavors will delve deeper into antigen-presenting cells and specific T cell subtypes to gain a more comprehensive understanding of the immune mechanisms at play in VLD.

Panniculitis, the inflammation of subcutaneous adipose tissue, has different clinical and dermatohistopathological phenotypes. The pathomechanisms underlying panniculitis remain largely unknown, with very limited studies showing a delayed-type III/IV hypersensitivity reaction. The aim of our study was to explore the cellular and molecular immune-patterns of two most common panniculitis subtypes, erythema nodosum (EN) and erythema induratum (EI) to gain new insights into their respective pathogenesis. We collected paraffin-embedded deep lesional skin biopsies of EN and EI patients (n=16 per group), as well as healthy controls (n=6). For an immune response-related gene expression analysis, we used bulk-RNA for NanoString. To characterize and map the leukocytic infiltrate, we used imaging mass cytometry (IMC). IMC analysis revealed distinct cellular profiles of EN and EI. In both conditions, macrophages were the most prominent immune cell type, showing a phenotypic shift from a M2- towards an M1-phenotype compared to healthy controls. EI showed a more prominent M1 and other immune cells infiltration. This was accompanied by a highly activated CD8+ T cell population, which clustered with M1 macrophages. In contrast, EN exhibited less inflammatory features and a larger B cell population. These cellular changes were paralleled by an overall strong type 1 immune signature on the mRNA level on both EN and EI. This was evidenced by a strong innate immune activation, with upregulation of NLR-, NFkB- and inflammasome-signaling-pathway genes compared to healthy controls. In line with IMC data, type I signature was more pronounced in EI compared with EN. Our cellular and molecular analyses can shift the current paradigm of panniculitis: EN and EI showed a strong type 1 immune response, which is mostly mediated by innate immune cells, namely M1 macrophages. We need to further explore the mechanisms of adipose tissue inflammation and how it could be therapeutically targeted.