Massive clonal expansion of polycytotoxic skin and blood CD8+ T cells in patients with toxic epidermal necrolysis

Endotypes in Immune Mediated Drug Reactions: Present and Future of Relevant Biomarkers. An EAACI Task Force Report

Drug-induced immune reactions are an important burden for patients and health systems. They can be classified into immediate-drug hypersensitivity reactions (IDHRs) and delayed-DHRs (DDHRs) based on their phenotype. Drugs do not always behave as allergens and need to bind to proteins, forming adducts. Therefore, IDHRs can be classified as antigenic (IgE, and IgG mediated) and nonantigenic immune responses (complement activation-[CARPA], mas-related G-protein coupled receptor member X2 [MRGPRX2], cyclooxygenase [COX]-1 and cytokine release reactions [CRRs]). DDHRs are even more complex due to the different cell subsets and mechanisms involved, showing both antigenic and nonantigenic immune responses too. Since different endotypes result in similar phenotypes, the establishment of specific biomarkers is essential for an accurate diagnosis, with important relevance for the management of patients, as well as for risk stratification. The biomarkers of clinical utility are skin tests, specific IgE (sIgE), tryptase, and some HLA-DR genotyping. The diagnostic performance depends on the responsible drug. This review highlights that, unfortunately, most biomarkers have not gone beyond analytic or clinical validity. It is therefore important to set up multicentre translational studies to advance the validation process towards reaching a clinical utility phase.

CCR8/CCL1 and CXCR3/CXCL10 axis-mediated memory T-cell activation in patients with recalcitrant drug-induced hypersensitivity

BACKGROUND

As a drug-induced hypersensitivity syndrome, drug reaction with eosinophilia and systemic symptoms (DRESS) is potentially fatal. Most patients with DRESS recover within a few weeks; however, some patients may suffer from a prolonged disease course and develop autoimmune sequelae.

OBJECTIVES

To investigate the immune mechanism and therapeutic targets of patients with recalcitrant DRESS with a prolonged disease course.

METHODS

Thirty-two patients with recalcitrant DRESS with a prolonged treatment course (≥ 8 weeks; 'prolonged DRESS'), 28 patients with DRESS with a short treatment course (< 2 weeks; 'short-duration DRESS') and 26 healthy donors (HDs) were enrolled.

RESULTS

Bulk transcriptome results showed that the mRNA expression levels of CCR8 and CXCR3 were significantly increased in blood samples from patients in the acute stage of prolonged DRESS [Padj = 1.50 × 10-9 (CCR8) and Padj = 2.60 × 10-4 (CXCR3), patients with prolonged DRESS compared with the HD group]. Serum and skin lesion concentrations of CCL1 and CXCL10 (ligands of CCR8 and CXCR3, respectively) were significantly increased in patients with prolonged DRESS compared with patients with short-duration DRESS. The results from high-parameter flow cytometry and autoantibody screening also identified significant increases in CD8+ GNLY+ CXCR3+ effector memory T cells, CD8+ central memory T cells, CD4+ CCR8+ T helper 2 cells and IgG anti-HES-6 autoantibodies in patients with prolonged DRESS. Furthermore, in vitro blocking assays revealed that Janus kinase inhibitors (JAKi; mainly tofacitinib and upadacitinib) significantly decreased the release of CCL1 and CXCL10. Some patients with prolonged DRESS were successfully treated with JAKi.

CONCLUSIONS

JAKi (tofacitinib and upadacitinib) were associated with decreased concentrations of CCL1 and CXCL10, suggesting that they may attenuate CCR8/CCL1 and CXCR3/CXCL10 axis-mediated memory T-cell activation, which contributes to disease pathogenesis in patients with recalcitrant DRESS and a long-term treatment course.

GRAPHICAL ABSTRACT

Delayed drug hypersensitivity reactions: How p-i transforms pharmacology into immunology

Delayed drug hypersensitivity reactions (dDHRs) are iatrogenic diseases, which are mostly due to non-covalent interactions of a drug with the immune receptors HLA and/or TCR causing T-cell activation. This is also known as pharmacological interaction with immune receptors or p-i. P-i activation differs from classical antigen-driven immune reactions: a) drug binding induces structural changes in TCR-HLA proteins which make them look like allo-like TCR-HLA-complexes, able to elicit allo-like stimulations of T cells with cytotoxicity and IFNγ production, notably without the involvement of innate immunity; b) drug binding to TCR and/or HLA can increase the affinity of TCR-HLA interactions, which may affect signaling and IL-5 production by CD4+ T cells, and thus contribute to eosinophilia commonly found in dDHRs or induce oligoclonal T cell expansions; c) Both, antigen and p-i stimulations can induce eosinophil- or neutrophil-rich inflammations; but these stimulations should be distinguished as their underlying mechanism and development differ; and d) p-i stimulation can - like graft versus host reactions - result in long-lasting T-cell activations, which can lead to viremia, occasional autoimmunity, or a new syndrome characterized by multiple drug hypersensitivity (MDH). In summary, dDHRs are not allergic reactions but represent peculiar T-cell activations, similar to allo-like stimulations. Understanding and considering the p-i mechanism is needed for preventive measures and optimal treatments of dDHR. In addition, it may help to understand TCR signaling, alloreactivity, and may even open a new way of specific immune stimulations.

Exploring recent advances in drugs severe cutaneous adverse reactions immunopathology

Severe cutaneous adverse reactions to drugs (SCARs) are rare but life-threatening delayed allergies. While they primarily affect the skin, they can also affect internal organs. Accordingly, they present with diverse clinical symptoms that vary not only between SCARs subtypes but also among patients. Despite the availability of topical and systemic treatments, these only address the symptoms and not the cause. To develop more effective therapies, it is necessary to elucidate the complexity of the pathophysiology of SCARs in relation to their severity. In line with the new type IV hypersensitivity reactions nomenclature proposed by the European Academy of Allergy and Clinical Immunology (EAACI), this review highlights the current insights into the intricate immune mechanisms engaged, the interplay between the culprit drug and genetic predisposition in drug presentation mechanisms, but also how external factors, such as viruses, are implicated in SCARs. Their relevance to the development of targeted medicine is also discussed.

Immune checkpoint inhibitor-induced severe epidermal necrolysis mediated by macrophage-derived CXCL10 and abated by TNF blockade

Immune checkpoint inhibitors (ICI) represent new anticancer agents and have been used worldwide. However, ICI can potentially induce life-threatening severe cutaneous adverse reaction (SCAR), such as Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), hindering continuous ICI therapy. We examine 6 cohorts including 25 ICI-induced SJS/TEN patients and conduct single-cell RNA sequencing (scRNA-seq) analysis, which shows overexpression of macrophage-derived CXCL10 that recruits CXCR3+ cytotoxic T lymphocytes (CTL) in blister cells from ICI-SJS/TEN skin lesions. ScRNA expression profiles and ex vivo blocking studies further identify TNF signaling as a pathway responsible for macrophage-derived CXCL10 and CTL activation. Based on the trajectory analysis, ICI-activated T cells from whole blood are proposed to serve as the initial cells involved in inflammation, that lead to monocytes differentiating into macrophages and increasing their susceptibility to migrate to the lesion sites. Compared with systemic corticosteroids treatment, ICI-induced SJS/TEN patients treated with biologic TNF blockade showed a significantly rapid recovery and no recurrence of SCAR with continuous ICI therapy. Our findings identify that macrophage-eliciting CTL contribute to the pathogenesis of ICI-induced epidermal necrolysis and provide potential therapeutic targets for the management and prevention of SCAR induced by ICI therapy.

Recent progress in Stevens-Johnson syndrome/toxic epidermal necrolysis: diagnostic criteria, pathogenesis and treatment

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) represent a severe spectrum of rare mucocutaneous reactions that are primarily drug-induced and characterized by significant morbidity and mortality. These conditions manifest in 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 advances in understanding the immunopathogenesis of SJS/TEN are explored, emphasizing the role of drug-specific T-cell responses and human leucocyte antigen polymorphisms in disease onset. The review also addresses current therapeutic approaches, including controversies surrounding the use of immunosuppressive agents and the emerging role of tumour necrosis factor-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 the disease and its mechanisms.

Oral Cyclosporine Treatment for Four Pediatric Patients With Toxic Epidermal Necrolysis That Showed No Response to High-dose Corticosteroids in Combination With Intravenous Immunoglobulin: A Case Series

Background

Immunosuppressive agents like cyclosporine have proven effective in some pediatric cases, although there are limited case reports considering potential risks such as secondary infections.

Objective

This study investigated the safety and efficacy of Cyclosporine A in children who did not respond to high-dose corticosteroids combined with intravenous immunoglobulin (IVIG).

Methods

We reported four pediatric patients diagnosed with toxic epidermal necrolysis (TEN) received treatment at our institution. All patients were previously healthy children with a median age of 7 years, comprising three boys and one girl (Table 1). Epidermal exfoliation and vesicular lesions ranged from 32.5% to 54.5% of the body surface area (BSA). Despite the administration of treatment comprising high-dose corticosteroids and intravenous immunoglobulin (IVIG), new cutaneous herpes continually emerged. This prompted a transition to cyclosporine treatment (3-5 mg/kg/d) administered in 1-2 oral doses.

Results

Lesions stopped progressing, and bullous lesions started epithelialization after 13-27 days of hospitalization. Cases 1 and 2 faced secondary bacterial and fungal infections, respectively, and their temperatures stabilized after administration of antibiotics. Cases 3 and 4 experienced fever again when the dosage of corticosteroids was tapered off, with no discernible evidence of infection. The patients' temperatures normalized upon the continuation of cyclosporine therapy. Among the patients, three presented asymptomatic elevated serum amylase, one of which met the diagnostic criteria for acute pancreatitis. Two children showed mildly raised aminotransferases, with one experiencing mild coronary artery dilation, two contracted onychomadesis, and three developed corneal ulceration/keratitis and atretoblepharia, which eventually resolved after vigorous ophthalmologic treatment. None of the children had any permanent sequelae after being discharged from the hospital for six months.

Conclusions

Cyclosporine A is generally safe and effective for children who fail to respond to high-dose corticosteroids in combination with IVIG.

Update on Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: Diagnosis and Management

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are the most severe cutaneous adverse reactions that are typically drug-induced in adults. Both SJS and TEN have high morbidity and mortality rates. SJS/TEN imposes clinical challenges for physicians managing patients suffering from this condition, both because it is rare and because it is a rapidly progressing systemic disease with severe cutaneous, mucosal, and systemic manifestations. Although many cases of SJS/TEN have been reported in the literature, there is no consensus regarding diagnostic criteria or treatment. Significant progress has been made in understanding its genetic predisposition and pathogenesis. This review is intended to provide physicians with a comprehensive but practical SJS/TEN roadmap to guide diagnosis and management. We review data on pathogenesis, reported precipitating factors, presentation, diagnosis, and management SJS/TEN focusing on what is new over the last 5 years.

Multiomic single-cell sequencing defines tissue-specific responses in Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is a rare but life-threatening cutaneous drug reaction mediated by human leukocyte antigen (HLA) class I-restricted CD8+ T cells. For unbiased assessment of cellular immunopathogenesis, here we perform single-cell (sc) transcriptome, surface proteome, and T cell receptor (TCR) sequencing on unaffected skin, affected skin, and blister fluid from 15 SJS/TEN patients. From 109,888 cells, we identify 15 scRNA-defined subsets. Keratinocytes express markers indicating HLA class I-restricted antigen presentation and appear to trigger the proliferation of and killing by cytotoxic CD8+ tissue-resident T cells that express granulysin, granzyme B, perforin, LAG3, CD27, and LINC01871, and signal through the PKM, MIF, TGFβ, and JAK-STAT pathways. In affected tissue, cytotoxic CD8+ T cells express private expanded and unexpanded TCRαβ that are absent or unexpanded in unaffected skin, and mixed populations of macrophages and fibroblasts express pro-inflammatory markers or those favoring repair. This data identifies putative cytotoxic TCRs and therapeutic targets.

Stevens-Johnson syndrome-toxic epidermal necrolysis overlap in a patient taking quetiapine and famotidine: a case report

BACKGROUND

Stevens-Johnson syndrome-toxic epidermal necrolysis (SJS-TNE) overlap is a rare skin disorder characterized by erythema, blisters, extensive exfoliation, epidermal detachment, the involvement of multiple mucosae, and positive Nikolsky's sign. SJS-TEN has a high mortality rate. Our case involves a rare occurrence of drug-induced Stevens-Johnson syndrome-toxic epidermal necrolysis overlap with a delayed onset in the setting of quetiapine and famotidine therapy.

CASE PRESENTATION

An 82-year-old Taiwanese female was admitted to our hospital for decreased urine output, generalized edema, and multiple skin blisters and bedsores. With further spread of the lesions, multiple ruptured bullae with shallow erosions on the face, trunk, and limbs and mucosal involvement affected 20% of the total body surface area. Nikolsky's sign was positive. A diagnosis of Steven-Johnson syndrome was highly suspected. One month prior, she had started famotidine and quetiapine. Intravenous methylprednisolone treatment was initiated, which ameliorated the skin lesions after 3 days. However, new lesions developed after only 1 day of methylprednisolone tapering. The patient died 12 days after admission.

CONCLUSION

Stevens-Johnson syndrome-toxic epidermal necrolysis is a rare skin disorder. Although it is mainly acute and has a high mortality rate, delayed onset can still occur. Quetiapine and famotidine are generally safe and effective for treating geriatric and gastrointestinal problems, but rare drug hypersensitivity reactions can lead to debilitating consequences. Therefore, increased clinical awareness and the initiation of supportive care are imperative. Optimal management guidelines are still lacking, and confirmation of developed guidelines through randomized controlled trials is needed. Collaboration for better management strategies is warranted.

Systemic and skin-limited delayed-type drug hypersensitivity reactions associate with distinct resident and recruited T cell subsets

Delayed-type drug hypersensitivity reactions are major causes of morbidity and mortality. The origin, phenotype, and function of pathogenic T cells across the spectrum of severity require investigation. We leveraged recent technical advancements to study skin-resident memory T cells (TRMs) versus recruited T cell subsets in the pathogenesis of severe systemic forms of disease, Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS), and skin-limited disease, morbilliform drug eruption (MDE). Microscopy, bulk transcriptional profiling, and single-cell RNA-sequencing (scRNA-Seq) plus cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq) plus T cell receptor sequencing (TCR-Seq) supported clonal expansion and recruitment of cytotoxic CD8+ T cells from circulation into skin along with expanded and nonexpanded cytotoxic CD8+ skin TRM in SJS/TEN. Comparatively, MDE displayed a cytotoxic T cell profile in skin without appreciable expansion and recruitment of cytotoxic CD8+ T cells from circulation, implicating TRMs as potential protagonists in skin-limited disease. Mechanistic interrogation in patients unable to recruit T cells from circulation into skin and in a parallel mouse model supported that skin TRMs were sufficient to mediate MDE. Concomitantly, SJS/TEN displayed a reduced Treg signature compared with MDE. DRESS demonstrated recruitment of cytotoxic CD8+ T cells into skin as in SJS/TEN, yet a pro-Treg signature as in MDE. These findings have important implications for fundamental skin immunology and clinical care.

Single-cell mass cytometry in immunological skin diseases

Immune-related skin diseases represent a collective of dermatological disorders intricately linked to dysfunctional immune system processes. These conditions are primarily characterized by an immoderate activation of the immune system or deviant immune responses, involving diverse immune components including immune cells, antibodies, and inflammatory mediators. However, the precise molecular dysregulation underlying numerous individual cases of these diseases and unique subsets respond under disease conditions remains elusive. Comprehending the mechanisms and determinants governing the homeostasis and functionality of diseases could offer potential therapeutic opportunities for intervention. Mass cytometry enables precise and high-throughput quantitative measurement of proteins within individual cells by utilizing antibodies labeled with rare heavy metal isotopes. Imaging mass cytometry employs mass spectrometry to obtain spatial information on cell-to-cell interactions within tissue sections, simultaneously utilizing more than 40 markers. The application of single-cell mass cytometry presents a unique opportunity to conduct highly multiplexed analysis at the single-cell level, thereby revolutionizing our understanding of cell population heterogeneity and hierarchy, cellular states, multiplexed signaling pathways, proteolysis products, and mRNA transcripts specifically in the context of many autoimmune diseases. This information holds the potential to offer novel approaches for the diagnosis, prognostic assessment, and monitoring responses to treatment, thereby enriching our strategies in managing the respective conditions. This review summarizes the present-day utilization of single-cell mass cytometry in studying immune-related skin diseases, highlighting its advantages and limitations. This technique will become increasingly prevalent in conducting extensive investigations into these disorders, ultimately yielding significant contributions to their accurate diagnosis and efficacious therapeutic interventions.

Drug hypersensitivity reactions: review of the state of the science for prediction and diagnosis

Drug hypersensitivity reactions (DHRs) are a type of adverse drug reaction that can occur with different classes of drugs and affect multiple organ systems and patient populations. DHRs can be classified as allergic or non-allergic based on the cellular mechanisms involved. Whereas nonallergic reactions rely mainly on the innate immune system, allergic reactions involve the generation of an adaptive immune response. Consequently, drug allergies are DHRs for which an immunological mechanism, with antibody and/or T cell, is demonstrated. Despite decades of research, methods to predict the potential for a new chemical entity to cause DHRs or to correctly attribute DHRs to a specific mechanism and a specific molecule are not well-established. This review will focus on allergic reactions induced by systemically administered low-molecular weight drugs with an emphasis on drug- and patient-specific factors that could influence the development of DHRs. Strategies for predicting and diagnosing DHRs, including potential tools based on the current state of the science, will also be discussed.

Toxic Epidermal Necrolysis Caused by Eribulin

Eribulin, a chemotherapy drug classified as a microtubule inhibitor, is known to target cell microtubule structures, impeding cancer cell growth and spread. This paper discusses a rare case of toxic epidermal necrolysis (TEN) induced by eribulin in a patient with angiosarcoma, marking it as an uncommon adverse reaction. This patient developed severe mucosal and skin lesions after the third dose of eribulin. Laboratory tests and a skin biopsy confirmed the diagnosis of TEN. The patient responded well to steroid therapy, although skin eruptions reoccurred with further eribulin treatment. This case highlights the need for further study on the immunological effects of eribulin, especially concerning severe drug eruptions potentially related to its impact on microtubule dynamics and immune cell functions.

Severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), which include Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (also known as drug-induced hypersensitivity syndrome), acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption, are life-threatening conditions. The pathogenesis of SCARs involves T cell receptors recognizing drug antigens presented by human leukocyte antigens, triggering the activation of distinct T cell subsets. These cells interact with keratinocytes and various immune cells, orchestrating cutaneous lesions and systemic manifestations. Genetic predisposition, impaired drug metabolism, viral reactivation or infections, and heterologous immunity influence SCAR development and clinical presentation. Specific genetic associations with distinct SCAR phenotypes have been identified, leading to the implementation of genetic screening before prescription in various countries to prevent SCARs. Whilst systemic corticosteroids and conventional immunomodulators have been the primary therapeutic agents, evolving strategies, including biologics and small molecules targeting tumour necrosis factor, different cytokines, or Janus kinase signalling pathways, signify a shift towards a precision management paradigm that considers individual clinical presentations.

Cutaneous adverse drug reactions

Cutaneous adverse drug reactions (ADRs) represent a heterogeneous field including various clinical patterns without specific features suggesting drug causality. Maculopapular exanthema and urticaria are the most common types of cutaneous ADR. Serious cutaneous ADRs, which may cause permanent sequelae or have fatal outcome, may represent 2% of all cutaneous ADR and must be quickly identified to guide their management. These serious reactions include bullous manifestations (epidermal necrolysis i.e. Stevens-Johnson syndrome and toxic epidermal necrolysis), drug reaction with eosinophilia and systemic symptoms (DRESS) and acute generalized exanthematous pustulosis (AGEP). Some risk factors for developing cutaneous ADRs have been identified, including immunosuppression, autoimmunity or genetic variants. All drugs can cause cutaneous ADRs, the most commonly implicated being antibiotics (especially aminopenicillins and sulfonamides), anticonvulsants, allopurinol, antineoplastic drugs, non-steroidal anti-inflammatory drugs and iodinated contrast media. Pathophysiology is related to immediate or delayed "idiosyncratic" immunologic mechanisms, i.e., usually not related to dose, and pharmacologic/toxic mechanisms, commonly dose-dependent and/or time-dependent. If an immuno-allergic mechanism is suspected, allergological explorations (including epicutaneous patch testing and/or intradermal test) are often possible to clarify drug causality, however these have a variable sensitivity according to the drug and to the ADR type. No in vivo or in vitro test can consistently confirm the drug causality. To determine the origin of a rash, a logical approach based on clinical characteristics, chronologic factors and elimination of differential diagnosis (especially infectious etiologies) is required, completed with a literature search. Reporting to pharmacovigilance system is therefore essential both to analyze drug causality at individual level, and to contribute to knowledge of the drug at population level, especially for serious cutaneous ADRs or in cases involving newly marketed drugs.

Why drug exposure is frequently associated with T-cell mediated cutaneous hypersensitivity reactions

Cutaneous hypersensitivity reactions represent the most common manifestation of drug allergy seen in the clinic, with 25% of all adverse drug reactions appearing in the skin. The severity of cutaneous eruptions can vastly differ depending on the cellular mechanisms involved from a minor, self-resolving maculopapular rash to major, life-threatening pathologies such as the T-cell mediated bullous eruptions, i.e., Stevens Johnson syndrome/toxic epidermal necrolysis. It remains a significant question as to why these reactions are so frequently associated with the skin and what factors polarise these reactions towards more serious disease states. The barrier function which the skin performs means it is constantly subject to a barrage of danger signals, creating an environment that favors elicitation. Therefore, a critical question is what drives the expansion of cutaneous lymphocyte antigen positive, skin homing, T-cell sub-populations in draining lymph nodes. One answer could be the heterologous immunity hypothesis whereby tissue resident memory T-cells that express T-cell receptors (TCRs) for pathogen derived antigens cross-react with drug antigen. A significant amount of research has been conducted on skin immunity in the context of contact allergy and the role of tissue specific antigen presenting cells in presenting drug antigen to T-cells, but it is unclear how this relates to epitopes derived from circulation. Studies have shown that the skin is a metabolically active organ, capable of generating reactive drug metabolites. However, we know that drug antigens are displayed systemically so what factors permit tolerance in one part of the body, but reactivity in the skin. Most adverse drug reactions are mild, and skin eruptions tend to be visible to the patient, whereas minor organ injury such as transient transaminase elevation is often not apparent. Systemic hypersensitivity reactions tend to have early cutaneous manifestations, the progression of which is halted by early diagnosis and treatment. It is apparent that the preference for cutaneous involvement of drug hypersensitivity reactions is multi-faceted, therefore this review aims to abridge the findings from literature on the current state of the field and provide insight into the cellular and metabolic mechanisms which may contribute to severe cutaneous adverse reactions.

Fatal toxic epidermal necrolysis associated with sinomenine in a patient with primary membranous nephropathy

Sinomenine (SIN), the alkaloid monomer extracted from Sinomenium acutum, is a kind of non-steroidal anti-inflammatory drug widely used in China to treat rheumatoid arthritis (RA) and various glomerular diseases. It has various pharmacological effects such as anti-inflammatory, analgesic, and anti-tumor. As a strong histamine-releasing agent, SIN has drawn increasing attention in regards to its side effects such as allergic, gastrointestinal, and circulatory systemic reactions. In this report, we first described a patient with primary membranous nephropathy (PMN) who was treated with oral intake of SIN and developed medicine-induced toxic epidermal necrolysis (TEN) and subsequently died of septic multi-organ failure. The present case report intends to demonstrate the underestimated side effects of SIN that can eventually lead to death.

Analysis of CD8+ TCRβ Chain repertoire in peripheral blood of vitiligo via high-throughput sequencing

Vitiligo is an autoimmune depigmentation dermatosis induced by melanocyte destruction, and CD8⁺ T cells play a pivotal role in melanocyte destruction. However, an accurate profile of the CD8⁺ T cell receptor (TCR) repertoire in vitiligo patients has not been reported, and the clonotype features of the involved CD8⁺ T cells remain largely unknown. This study aimed to assess the TCRβ chain repertoire diversity and composition of blood in nine nonsegmental vitiligo patients via high-throughput sequencing. Vitiligo patients manifested a low TCRβ repertoire diversity with highly expanded clones. Differential usage of TRBV, the TRBJ gene, and the TRBV/TRBJ combination were compared between patients with vitiligo and healthy controls. A set of TRBV/TRBJ combinations could differentiate patients with vitiligo from healthy controls (area under the curve = 0.9383, 95% CI: 0.8167-1.00). Our study revealed distinct TCRβ repertoires of CD8⁺ T cells in patients with vitiligo and will help explore novel immune biomarkers and potential therapeutic targets for vitiligo.

Functional heterogeneity of human skin-resident memory T cells in health and disease

The human skin is populated by a diverse pool of memory T cells, which can act rapidly in response to pathogens and cancer antigens. Tissue-resident memory T cells (TRM ) have been implicated in range of allergic, autoimmune and inflammatory skin diseases. Clonal expansion of cells with TRM properties is also known to contribute to cutaneous T-cell lymphoma. Here, we review the heterogeneous phenotypes, transcriptional programs, and effector functions of skin TRM . We summarize recent studies on TRM formation, longevity, plasticity, and retrograde migration and contextualize the findings to skin TRM and their role in maintaining skin homeostasis and altered functions in skin disease.

Outcomes Associated With Neutropenia and Lymphopenia in Epidermal Necrolysis: A Single-Center Retrospective Study of 147 Patients

This retrospective cohort study examines the association of lymphocyte and neutrophil levels with treatment outcomes in 147 patients with epidermal necrolysis in France.

Updates on the immunopathology and genomics of severe cutaneous adverse drug reactions

Severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome, toxic epidermal necrolysis (SJS/TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS) cause significant morbidity and mortality and impede new drug development. HLA class I associations with SJS/TEN and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome have aided preventive efforts and provided insights into immunopathogenesis. In SJS/TEN, HLA class I-restricted oligoclonal CD8+ T-cell responses occur at the tissue level. However, specific HLA risk allele(s) and antigens driving this response have not been identified for most drugs. HLA risk alleles also have incomplete positive and negative predictive values, making truly comprehensive screening currently challenging. Although, there have been key paradigm shifts in knowledge regarding drug hypersensitivity, there are still many open and unanswered questions about SCAR immunopathogenesis, as well as genetic and environmental risk. In addition to understanding the cellular and molecular basis of SCAR at the single-cell level, identification of the MHC-restricted drug-reactive self- or viral peptides driving the hypersensitivity reaction will also be critical to advancing premarketing strategies to predict risk at an individual and drug level. This will also enable identification of biologic markers for earlier diagnosis and accurate prognosis, as well as drug causality and targeted therapeutics.

Viral infections and drug hypersensitivity

Virus infections and T-cell-mediated drug hypersensitivity reactions (DHR) can influence each other. In most instances, systemic virus infections appear first. They may prime the reactivity to drugs in two ways: First, by virus-induced second signals: certain drugs like β-lactam antibiotics are haptens and covalently bind to various soluble and tissue proteins, thereby forming novel antigens. Under homeostatic conditions, these neo-antigens do not induce an immune reaction, probably because co-stimulation is missing. During a virus infection, the hapten-modified peptides are presented in an immune-stimulatory environment with co-stimulation. A drug-specific immune reaction may develop and manifest as exanthema. Second, by increased pharmacological interactions with immune receptors (p-i): drugs tend to bind to proteins and may even bind to immune receptors. Without viral infections, this low affine binding may be insufficient to elicit T-cell activation. During a viral infection, immune receptors are more abundantly expressed and allow more interactions to occur. This increases the overall avidity of p-i reactions and may even be sufficient for T-cell activation and symptoms. There is a situation where the virus-DHR sequence of events is inversed: in drug reaction with eosinophilia and systemic symptoms (DRESS), a severe DHR can precede reactivation and viremia of various herpes viruses. One could explain this phenomenon by the massive p-i mediated immune stimulation during acute DRESS, which coincidentally activates many herpes virus-specific T cells. Through p-i stimulation, they develop a cytotoxic activity by killing herpes peptide-expressing cells and releasing herpes viruses. These concepts could explain the often transient nature of DHR occurring during viral infections and the often asymptomatic herpes-virus viraemia after DRESS.

Advances in the Understanding of Drug Hypersensitivity: 2012 Through 2022

Over the last decade there have been key advances in understanding mechanisms, risk, and consequences of both true immunological drug hypersensitivity and unverified drug allergy labels that have changed clinical practice. This has been facilitated by the widespread adoption of electronic health records (EHRs). The vast majority of EHR drug allergy labels are unverified and cause significant morbidity from unnecessary avoidance of optimal drug therapy. There has also been significant movement in our understanding of mechanisms of drug hypersensitivity that, in addition to advancing our understanding of the pathogenesis of immediate and delayed reactions, have guided preventive efforts, diagnostic procedures, and clinical management. More widespread adoption, including scale-up of "allergy" delabeling and appropriate management, specifically for antibiotics, opiates, radiocontrast, chemotherapeutics, biologics, and nonsteroidal anti-inflammatory medications, will be necessary to improve patient outcomes over the next decade. This will require further engagement and collaboration between primary care health care providers, allergists, and other specialists.

[Research advances on burn blister fluid]

Burns often cause the damaged tissue to produce a large amount of exudate and the formation of blisters on the wound. The burn blister fluid contains a large number of molecules related to wound healing, which can reflect the state of local tissue microenvironment of the burn wound. Analyzing relevant information such as cellular components, signal mediators, and protein molecules in burn blister fluid is helpful to understand the local reaction and tissue microenvironment of burn wounds, and then help clinical burn treatment. In this article, by understanding the production mechanism of burn blister fluid, discussing its role in wound evaluation, and integrating the research progress of burn blister fluid in proteomics, metabolomics, cellular components, and pharmacokinetics, we propose our thoughts and prospects on the research of burn blister fluid, in order to provide assistance for clinical evaluation and treatment of burn wounds, and also provide idea for the follow-up study of burn blister fluid.

IL-15/IL-15Rα in SJS/TEN: Relevant Expression of IL15 and IL15RA in Affected Skin

Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a life-threatening hypersensitivity reaction to medications characterized by keratinocyte apoptosis and skin detachment. IL-15 serum levels have been associated with severity and prognosis of SJS/TEN. We have measured IL-15 concentrations in serum and blister fluid (BF) from patients with SJS/TEN by ELISA and used quantitative RT-PCR to analyze the expression of IL15 and IL15RA (encoding for IL-15 Receptor-α chain) genes in peripheral blood and BF cells, including isolated monocytes, and in affected skin. A positive correlation was found between IL-15 serum levels and a percent of detached skin. BF concentrations were higher, but no correlation was found. Higher IL15 and IL15RA gene expression levels were found in skin-infiltrating blister fluid cells compared to peripheral mononuclear cells. Moreover, IL15RA transcripts were barely detected in healthy skin, being the highest expression levels found in samples from two SJS/TEN patients who did not survive. The cutaneous expression of IL-15Rα in SJS/TEN may provide an explanation to the tissue-specific immune cytotoxic response in this clinical entity, and the results suggest that the effects of IL-15 in SJS/TEN patients may be dependent on the expression of its private receptor IL-15Rα in affected skin.

Practical Implementation of Genetics: New Concepts in Immunogenomics to Predict, Prevent, and Diagnose Drug Hypersensitivity

Delayed drug hypersensitivities are CD8⁺ T cell-mediated reactions associated with up to 50% mortality. Human leukocyte antigen (HLA) alleles are known to predispose disease and are specific to drug, reaction, and patient ethnicity. Pretreatment screening is recommended for a handful of the strongest associations to identify and prevent drug use in high-risk patients. However, an incomplete predictive value implicates other HLA-imposed risk factors, and low carriage of many identified HLA-risk alleles combined with the high cost of sequence-based typing has limited economic viability for similar recommendation of screening across drugs and health care systems. For mitigation, an expanding armory of low-cost polymerase chain reaction-based screens is being developed, and HLA-imposed risk factors are being discovered. These include (1) polymorphic variants of metabolic and endoplasmic reticulum aminopeptidase enzymes toward multiallelic screening with increased predictivity; (2) regulation by immune checkpoint inhibitors, enabling detolerized animal models of human disease; and (3) immunodominant T cell receptors (TCR) on clonally expanded CD8⁺ T cells. For the latter, HLA risk-restricted TCR provides immunogenomic strategies and samples from a single patient to identify novel HLA-risk associations in underserved minority populations, tissue-relevant effector biomarkers toward earlier diagnosis and treatment, and HLA-TCR-presented immunogenic structures to aid future drug development.

Advances in Our Understanding of the Interaction of Drugs with T-cells: Implications for the Discovery of Biomarkers in Severe Cutaneous Drug Reactions

Drugs can activate different cells of the immune system and initiate an immune response that can lead to life-threatening diseases collectively known as severe cutaneous adverse reactions (SCARs). Antibiotics, anticonvulsants, and antiretrovirals are involved in the development of SCARs by the activation of αβ naïve T-cells. However, other subsets of lymphocytes known as nonconventional T-cells with a limited T-cell receptor repertoire and innate and adaptative functions also recognize drugs and drug-like molecules, but their role in the pathogenesis of SCARs has only just begun to be explored. Despite 30 years of advances in our understanding of the mechanisms in which drugs interact with T-cells and the pathways for tissue injury seen during T-cell activation, at present, the development of useful clinical biomarkers for SCARs or predictive preclinical in vitro assays that could identify immunogenic moieties during drug discovery is an unmet goal. Therefore, the present review focuses on (i) advances in the understanding of the pathogenesis of SCARs reactions, (ii) a description of the interaction of drugs with conventional and nonconventional T-cells, and (iii) the current state of soluble blood circulating biomarker candidates for SCARs.

Advances in the Pathomechanisms of Delayed Drug Hypersensitivity

Delayed drug hypersensitivity continues to contribute to major clinical problems worldwide. The clinical presentations of delayed drug hypersensitivity are diverse, ranging from mild skin rashes to life-threatening systemic reactions. The pathomechanism of delayed drug hypersensitivity involves human leukocyte antigens (HLA) presentation of drugs/metabolites to T cell receptors (TCR), resulting in T-cell activation. The pathogenesis of delayed drug hypersensitivity also has reactivation of the virus, and activation of many immune mediators. In this review, we discuss the immune pathogenesis, molecular interactions of HLA/drugs/TCR, and downstream signaling of cytotoxic proteins/cytokines/chemokines, as well as disease prevention and management for delayed drug hypersensitivity.

Risk Assessment in Drug Hypersensitivity: Detecting Small Molecules Which Outsmart the Immune System

Drug hypersensitivity (DH) reactions are clinically unusual because the underlying immune stimulations are not antigen-driven, but due to non-covalent drug-protein binding. The drugs may bind to immune receptors like HLA or TCR which elicits a strong T cell reaction (p-i concept), the binding may enhance the affinity of antibodies (enhanced affinity model), or drug binding may occur on soluble proteins which imitate a true antigen (fake antigen model). These novel models of DH could have a major impact on how to perform risk assessments in drug development. Herein, we discuss the difficulties of detecting such non-covalent, labile and reversible, but immunologically relevant drug-protein interactions early on in drug development. The enormous diversity of the immune system, varying interactions, and heterogeneous functional consequences make it to a challenging task. We propose that a realistic approach to detect clinically relevant non-covalent drug interactions for a new drug could be based on a combination of in vitro cell culture assays (using a panel of HLA typed donor cells) and functional analyses, supplemented by structural analysis (computational data) of the reactive cells/molecules. When drug-reactive cells/molecules with functional impact are detected in these risk assessments, a close clinical monitoring of the drug may reveal the true incidence of DH, as suppressing but also enhancing factors occurring in vivo can influence the clinical manifestation of a DH.

Frequencies and TCR Repertoires of Human 2,4,6-Trinitrobenzenesulfonic Acid-specific T Cells

Allergic contact dermatitis is a widespread T cell-mediated inflammatory skin disease, but in vitro monitoring of chemical-specific T cells remains challenging. We here introduce short-term CD154/CD137 upregulation to monitor human T cell responses to the experimental sensitizer 2,4,6-trinitrobenzenesulfonic acid (TNBS). Peripheral blood mononuclear cells (PBMC) from healthy donor buffy coats were TNBS-modified and incubated with unmodified PBMC. After 5 and 16 h, we detected TNBS-specific activated CD154+CD4+ and CD137+CD8+ T cells by multi-parameter flow cytometry, respectively. Activated cells were sorted for restimulation and bulk T cell receptor (TCR) high-throughput sequencing (HTS). Stimulation with TNBS-modified cells (3 mM) induced CD154 expression on 0.04% of CD4+ and CD137 expression on 0.60% of CD8+ memory T cells, respectively (means, n = 11-17 donors). CD69 co-expression argued for TCR-mediated activation, which was further supported by TNBS-specific restimulation of 10/13 CD154+CD4+ and 11/15 CD137+CD8+ T cell clones and lines. Major histocompatibility complex (MHC) blocking antibodies prevented activation, illustrating MHC restriction. The high frequencies of TNBS-specific T cells were associated with distinct common changes in the TCR β-chain repertoire. We observed an overrepresentation of tryptophan and lysine in the complementarity determining regions 3 (CDR3) (n = 3-5 donors), indicating a preferential interaction of these amino acids with the TNBS-induced epitopes. In summary, the detection of TNBS-specific T cells by CD154/CD137 upregulation is a fast, comprehensive and quantitative method. Combined with TCR HTS, the mechanisms of chemical allergen recognition that underlie unusually frequent T cell activation can be assessed. In the future, this approach may be adapted to detect T cells activated by additional chemical sensitizers.

In Vitro Monitoring of Human T Cell Responses to Skin Sensitizing Chemicals-A Systematic Review

Background: Chemical allergies are T cell-mediated diseases that often manifest in the skin as allergic contact dermatitis (ACD). To prevent ACD on a public health scale and avoid elicitation reactions at the individual patient level, predictive and diagnostic tests, respectively, are indispensable. Currently, there is no validated in vitro T cell assay available. The main bottlenecks concern the inefficient generation of T cell epitopes and the detection of rare antigen-specific T cells. Methods: Here, we systematically review original experimental research papers describing T cell activation to chemical skin sensitizers. We focus our search on studies published in the PubMed and Scopus databases on non-metallic allergens in the last 20 years. Results: We identified 37 papers, among them 32 (86%) describing antigen-specific human T cell activation to 31 different chemical allergens. The remaining studies measured the general effects of chemical allergens on T cell function (five studies, 14%). Most antigen-specific studies used peripheral blood mononuclear cells (PBMC) as antigen-presenting cells (APC, 75%) and interrogated the blood T cell pool (91%). Depending on the individual chemical properties, T cell epitopes were generated either by direct administration into the culture medium (72%), separate modification of autologous APC (29%) or by use of hapten-modified model proteins (13%). Read-outs were mainly based on proliferation (91%), often combined with cytokine secretion (53%). The analysis of T cell clones offers additional opportunities to elucidate the mechanisms of epitope formation and cross-reactivity (13%). The best researched allergen was p-phenylenediamine (PPD, 12 studies, 38%). For this and some other allergens, stronger immune responses were observed in some allergic patients (15/31 chemicals, 48%), illustrating the in vivo relevance of the identified T cells while detection limits remain challenging in many cases. Interpretation: Our results illustrate current hardships and possible solutions to monitoring T cell responses to individual chemical skin sensitizers. The provided data can guide the further development of T cell assays to unfold their full predictive and diagnostic potential, including cross-reactivity assessments.

Immunopharmacogenomics: Mechanisms of HLA-Associated Drug Reactions

The human leukocyte antigen (HLA) system is the most polymorphic in the human genome that has been associated with protection and predisposition to a broad array of infectious, autoimmune, and malignant diseases. More recently over the last two decades, HLA class I alleles have been strongly associated with T-cell-mediated drug hypersensitivity reactions. In the case of abacavir hypersensitivity and HLA-B*57:01, the 100% negative predictive value and low number needed to test to prevent a single case has led to a durable and effective global preprescription screening strategy. However, HLA associations are still undefined for most drugs clinically associated with different delayed drug hypersensitivity phenotypes, and an HLA association relevant to one population is not generalizable across ethnicities. Furthermore, while a specific risk HLA allele is necessary for drug-induced T-cell activation, it is not sufficient. The low and incomplete positive predictive value has hindered efforts at clinical implementation for many drugs but has provided the impetus to understand the mechanisms of HLA class I restricted T-cell-mediated drug hypersensitivity reactions. Current research has focused on defining the contribution of additional elements of the adaptive immune response and other genetic and ecologic risk factors that contribute to drug hypersensitivity risk. In this review we focus on new insights into immunological, pharmacological, and genetic mechanisms underpinning HLA-associated drug reactions and the implications for future translation into clinical care.