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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.

Importance: Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare but potentially fatal drug hypersensitivity reaction. To our knowledge, there is no international consensus on its severity assessment and treatment., Objective: To reach an international, Delphi-based multinational expert consensus on the diagnostic workup, severity assessment, and treatment of patients with DRESS., Design, Setting, and Participants: The Delphi method was used to assess 100 statements related to baseline workup, evaluation of severity, acute phase, and postacute management of DRESS. Fifty-seven international experts in DRESS were invited, and 54 participated in the survey, which took place from July to September 2022., Main Outcomes/measures: The degree of agreement was calculated with the RAND-UCLA Appropriateness Method. Consensus was defined as a statement with a median appropriateness value of 7 or higher (appropriate) and a disagreement index of lower than 1., Results: In the first Delphi round, consensus was reached on 82 statements. Thirteen statements were revised and assessed in a second round. A consensus was reached for 93 statements overall. The experts agreed on a set of basic diagnostic workup procedures as well as severity- and organ-specific further investigations. They reached a consensus on severity assessment (mild, moderate, and severe) based on the extent of liver, kidney, and blood involvement and the damage of other organs. The panel agreed on the main lines of DRESS management according to these severity grades. General recommendations were generated on the postacute phase follow-up of patients with DRESS and the allergological workup., Conclusions and Relevance: This Delphi exercise represents, to our knowledge, the first international expert consensus on diagnostic workup, severity assessment, and management of DRESS. This should support clinicians in the diagnosis and management of DRESS and constitute the basis for development of future guidelines.

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) is a predominantly drug-induced disease, with a mortality rate of 15-20%, that engages the expertise of multiple disciplines: dermatology, allergy, immunology, clinical pharmacology, burn surgery, ophthalmology, urogynecology, and psychiatry. SJS/TEN has an incidence of 1-5/million persons per year in the United States, with even higher rates globally. One of the challenges of SJS/TEN has been developing the research infrastructure and coordination to answer questions capable of transforming clinical care and leading to improved patient outcomes. SJS/TEN 2021, the third research meeting of its kind, was held as a virtual meeting on August 28-29, 2021. The meeting brought together 428 international scientists, in addition to a community of 140 SJS/TEN survivors and family members. The goal of the meeting was to brainstorm strategies to support the continued growth of an international SJS/TEN research network, bridging science and the community. The community workshop section of the meeting focused on eight primary themes: mental health, eye care, SJS/TEN in children, non-drug induced SJS/TEN, long-term health complications, new advances in mechanisms and basic science, managing long-term scarring, considerations for skin of color, and COVID-19 vaccines. The meeting featured several important updates and identified areas of unmet research and clinical need that will be highlighted in this white paper., Competing Interests: KM was employed by Stevens-Johnson Syndrome Foundation. EJP reports grants from National Institutes of Health (R01HG010863, R01AI152183, U01AI154659) and from the National Health and Medical Research Council of Australia. She receives Royalties and consulting fees from UpToDate and has received consulting fees from Janssen, Verve, Biocryst, Regeneron, AstraZeneca and Novavax. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer OI declared a shared affiliation with the author AS to the handling editor at the time of review., (Copyright © 2023 Marks, Botta, Abe, Beachkofsky, Boothman, Carleton, Chung, Cibotti, Dodiuk-Gad, Grimstein, Hasegawa, Hoofnagle, Hung, Kaffenberger, Kroshinsky, Lehloenya, Martin-Pozo, Micheletti, Mockenhaupt, Nagao, Pakala, Palubinsky, Pasieka, Peter, Pirmohamed, Reyes, Saeed, Shupp, Sukasem, Syu, Ueta, Zhou, Chang, Becker, Bellon, Bonnet, Cavalleri, Chodosh, Dewan, Dominguez, Dong, Ezhkova, Fuchs, Goldman, Himed, Mallal, Markova, McCawley, Norton, Ostrov, Phan, Sanford, Schlundt, Schneider, Shear, Shinkai, Tkaczyk, Trubiano, Volpi, Bouchard, Divito and Phillips.)

Importance: Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a severe hypersensitivity reaction. Identifying a culprit drug is critical for patient care, yet identification is based on clinical judgment. Data are limited on the accuracy in or approach to identifying a culprit drug., Objective: To evaluate patient allergy list outcomes, current approaches in identifying culprit drugs, and potential methods of improving culprit drug identification., Design, Setting, and Participants: This retrospective cohort study spanned 18 years (January 2000 to July 2018), was conducted at Brigham and Women's Hospital and Massachusetts General Hospital (Boston), and included patients with clinically and histologically confirmed cases of SJS/TEN overlap and TEN., Main Outcomes and Measures: This study descriptively analyzed potential culprits to SJS/TEN, patients' allergy lists, and currently used approaches that led to those lists. It then tested the theoretical contribution of incorporating various parameters to allergy list outcomes., Results: Of 48 patients (29 women [60.4%]; 4 Asian [8.3%], 6 Black [12.5%], 5 Hispanic [10.4%], and 25 White [52.1%] individuals; median age, 40 years [range, 1-82 years]), the mean (SD) number of drugs taken per patient at disease onset was 6.5 (4.7). Physicians labeled 17 patients as allergic to a single culprit drug. Comparatively, 104 drugs were added to allergy lists across all patients. Physicians' approaches relied largely on heuristic identification of high-notoriety drugs and the timing of drug exposure. Use of a vetted database for drug risk improved sensitivity. Algorithm for Drug Causality for Epidermal Necrolysis scoring was discordant in 28 cases, labeling an additional 9 drugs missed by physicians and clearing 43 drugs labeled as allergens by physicians. Human leukocyte antigen testing could have potentially affected 20 cases. Consideration of infection as a culprit was limited., Conclusions and Relevance: The results of this cohort study suggest that currently used approaches to identify culprit drugs in SJS/TEN are associated with overlabeling patients allergic to likely nonculprit drugs and less commonly missed possible culprit drugs. Incorporation of a systematized unbiased approach could potentially improve culprit drug identification, although ultimately a diagnostic test is necessary.

Skin diseases are hallmarks of progressive HIV-related immunosuppression, with severe noninfectious inflammatory and hypersensitivity conditions as common as opportunistic infections. Conditions such as papular pruritic eruption are AIDS defining, whereas delayed immune-mediated adverse reactions, mostly cutaneous, occur up to 100-fold more during HIV infection. The skin, constantly in contact with the external environment, has a complex immunity. A dense, tightly junctioned barrier with basal keratinocytes and epidermal Langerhans cells with antimicrobial, innate-activating, and antigen-presenting functions form the frontline. Resident dermal dendritic, mast, macrophage, and innate lymphoid cells play pivotal roles in directing and polarizing appropriate adaptive immune responses and directing effector immune cell trafficking. Sustained viral replication leads to progressive declines in CD4 T cells, whereas Langerhans and dermal dendritic cells serve as viral reservoirs and points of first viral contact in the mucosa. Cutaneous cytokine responses and diminished lymphoid populations create a crucible for exaggerated inflammation and hypersensitivity. However, beyond histopathological description, these manifestations are poorly characterized. This review details normal skin immunology, changes associated with progressive HIV-related immunosuppression, and the characteristic conditions of immune dysregulation increased with HIV. We highlight the main research gaps and several novel tissue-directed strategies to define mechanisms that will provide targeted approaches to prevention or treatment., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Competing Interests: None disclosed.

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., Competing Interests: Disclosure The authors have declared that they have no conflicts of interest., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Delayed-type drug hypersensitivity reactions (dtDHR) are immune-mediated reactions with skin and visceral manifestations ranging from mild to severe. Clinical care is negatively impacted by a limited understanding of disease pathogenesis. Though T cells are believed to orchestrate disease, the type of T cell and the location and mechanism of T cell activation remain unknown. Resident memory T cells (T RM ) are a unique T cell population potentially well situated to act as key mediators in disease pathogenesis, but significant obstacles to defining, identifying, and testing T RM in dtDHR preclude definitive conclusions at this time. Deeper mechanistic interrogation to address these unanswered questions is necessary, as involvement of T RM in disease has significant implications for prediction, diagnosis, and treatment of disease., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Schunkert, Shah and Divito.)

Purpose of Review: To provide updates on recent advances in the diagnosis and management of drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome., Recent Findings: The number of identified HLA allele associations with DRESS continues to grow. There is increasing evidence indicating viral infection, reactivation, and cross-reactivity may play key roles in disease. Translational work illuminated JAK/STAT activation in recalcitrant disease. There is expanding recognition of rapid-onset DRESS resulting from specific drugs., Summary: DRESS is a severe form of adverse drug reaction with potential for significant morbidity and mortality. Recent research advances may improve clinical care. HLA screening can now be performed to prevent disease in susceptible patients and may help identify culprit drugs in the near future. Viral testing should be performed on every patient, and if positive, patients potentially treated with antiviral therapy. JAK inhibitors may be an effective treatment option for DRESS. Early onset of disease relative to drug exposure should not exclude the diagnosis of DRESS., Competing Interests: Conflict of InterestThe authors have no conflicts of interest to declare., (© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021.)

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in hematopoietic stem cell transplantation (HSCT). Donor T cells are key mediators in pathogenesis, but a contribution from host T cells has not been explored, as conditioning regimens are believed to deplete host T cells. To evaluate a potential role for host T cells in GVHD, the origin of skin and blood T cells was assessed prospectively in patients after HSCT in the absence of GVHD. While blood contained primarily donor-derived T cells, most T cells in the skin were host derived. We next examined patient skin, colon, and blood during acute GVHD. Host T cells were present in all skin and colon acute GVHD specimens studied, yet were largely absent in blood. We observed acute skin GVHD in the presence of 100% host T cells. Analysis demonstrated that a subset of host T cells in peripheral tissues were proliferating (Ki67+) and producing the proinflammatory cytokines IFN-γ and IL-17 in situ. Comparatively, the majority of antigen-presenting cells (APCs) in tissue in acute GVHD were donor derived, and donor-derived APCs were observed directly adjacent to host T cells. A humanized mouse model demonstrated that host skin-resident T cells could be activated by donor monocytes to generate a GVHD-like dermatitis. Thus, host tissue-resident T cells may play a previously unappreciated pathogenic role in acute GVHD.

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are potentially life-threatening, immune-mediated adverse reactions characterized by widespread erythema, epidermal necrosis, and detachment of skin and mucosa. Efforts to grow and develop functional international collaborations and a multidisciplinary interactive network focusing on SJS/TEN as an uncommon but high burden disease will be necessary to improve efforts in prevention, early diagnosis and improved acute and long-term management. SJS/TEN 2019: From Science to Translation was a 1.5-day scientific program held April 26-27, 2019, in Vancouver, Canada. The meeting successfully engaged clinicians, researchers, and patients and conducted many productive discussions on research and patient care needs., (Crown Copyright © 2020. Published by Elsevier B.V. All rights reserved.)

During that past two decades, advances in techniques for generating in vitro immune-suppressive dendritic cells (DCs) have heralded the use of these pro-tolerogenic DCs as therapeutics against transplant rejection and autoimmune diseases. In transplantation, previous dogma assumed that systemically administered therapeutic DCs bearing donor antigens (Ags) control the anti-donor response by directly interacting with anti-donor T cells in vivo. However, recent evidence indicates that the exogenously-administered therapeutic DCs instead function as Ag-transporting cells that transfer donor Ags to recipient's Ag-presenting cells (APCs) for presentation to T cells. In secondary lymphoid organs, presentation of acquired donor Ags by recipient's quiescent DCs triggers deficient activation and eventual apoptosis of donor-specific effector T cells, leading to a relative increase in the percentage of donor-specific regulatory T cells. This chapter describes the methodology to generate in vitro immune-suppressive DCs that are resistant to maturation, and to assess in vivo both their survival and their ability to regulate donor-specific T cells in a mouse model.

Mycosis fungoides (MF), the most common cutaneous T cell lymphoma (CTCL) is a malignancy of skin-tropic memory T cells. Most MF cases present as early stage (stage I A/B, limited to the skin), and these patients typically have a chronic, indolent clinical course. However, a small subset of early-stage cases develop progressive and fatal disease. Because outcomes can be so different, early identification of this high-risk population is an urgent unmet clinical need. We evaluated the use of next-generation high-throughput DNA sequencing of the T cell receptor β gene ( TCRB ) in lesional skin biopsies to predict progression and survival in a discovery cohort of 208 patients with CTCL (177 with MF) from a 15-year longitudinal observational clinical study. We compared these data to the results in an independent validation cohort of 101 CTCL patients (87 with MF). The tumor clone frequency (TCF) in lesional skin, measured by high-throughput sequencing of the TCRB gene, was an independent prognostic factor of both progression-free and overall survival in patients with CTCL and MF in particular. In early-stage patients, a TCF of >25% in the skin was a stronger predictor of progression than any other established prognostic factor (stage IB versus IA, presence of plaques, high blood lactate dehydrogenase concentration, large-cell transformation, or age). The TCF therefore may accurately predict disease progression in early-stage MF. Early identification of patients at high risk for progression could help identify candidates who may benefit from allogeneic hematopoietic stem cell transplantation before their disease becomes treatment-refractory., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Although rare, Stevens-Johnson syndrome and toxic epidermal necrolysis remain among the most devastating of acute conditions involving the skin. In the past 30 years, tremendous progress has been made in understanding the causes and pathobiology of this often life-threatening condition. Su et al demonstrate associations between IL 15 serum levels and the outcome of patients with Stevens-Johnson syndrome and toxic epidermal necrolysis. Their findings provide ideas for further investigations that may help us better understand the role of cytokines in this T-cell mediate disease and provides clues to possible new therapies., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Tissue-resident memory T (T RM ) cells persist indefinitely in epithelial barrier tissues and protect the host against pathogens. However, the biological pathways that enable the long-term survival of T RM cells are obscure. Here we show that mouse CD8 + T RM cells generated by viral infection of the skin differentially express high levels of several molecules that mediate lipid uptake and intracellular transport, including fatty-acid-binding proteins 4 and 5 (FABP4 and FABP5). We further show that T-cell-specific deficiency of Fabp4 and Fabp5 (Fabp4/Fabp5) impairs exogenous free fatty acid (FFA) uptake by CD8 + T RM cells and greatly reduces their long-term survival in vivo, while having no effect on the survival of central memory T (T CM ) cells in lymph nodes. In vitro, CD8 + T RM cells, but not CD8 + T CM cells, demonstrated increased mitochondrial oxidative metabolism in the presence of exogenous FFAs; this increase was not seen in Fabp4/Fabp5 double-knockout CD8 + T RM cells. The persistence of CD8 + T RM cells in the skin was strongly diminished by inhibition of mitochondrial FFA β-oxidation in vivo. Moreover, skin CD8 + T RM cells that lacked Fabp4/Fabp5 were less effective at protecting mice from cutaneous viral infection, and lung Fabp4/Fabp5 double-knockout CD8 + T RM cells generated by skin vaccinia virus (VACV) infection were less effective at protecting mice from a lethal pulmonary challenge with VACV. Consistent with the mouse data, increased FABP4 and FABP5 expression and enhanced extracellular FFA uptake were also demonstrated in human CD8 + T RM cells in normal and psoriatic skin. These results suggest that FABP4 and FABP5 have a critical role in the maintenance, longevity and function of CD8 + T RM cells, and suggest that CD8 + T RM cells use exogenous FFAs and their oxidative metabolism to persist in tissue and to mediate protective immunity.

Focal dermal hypoplasia (FDH) is an X-linked dominant disease characterized by dermal thinning and fat herniation with other ectodermal and mesodermal abnormalities. There is limited literature regarding the symptomatology and progression of skin, hair, and nail disease. The risk of bone fragility has not been explored either. This cross-sectional survey-based study explored these gaps in knowledge and provides direction for future avenues of research in FDH., (© 2016 Wiley Periodicals, Inc.)

Successful engraftment of organ transplants has traditionally relied on preventing the activation of recipient (host) T cells. Once T-cell activation has occurred, however, stalling the rejection process becomes increasingly difficult, leading to graft failure. Here we demonstrate that graft-infiltrating, recipient (host) dendritic cells (DCs) play a key role in driving the rejection of transplanted organs by activated (effector) T cells. We show that donor DCs that accompany heart or kidney grafts are rapidly replaced by recipient DCs. The DCs originate from non-classical monocytes and form stable, cognate interactions with effector T cells in the graft. Eliminating recipient DCs reduces the proliferation and survival of graft-infiltrating T cells and abrogates ongoing rejection or rejection mediated by transferred effector T cells. Therefore, host DCs that infiltrate transplanted organs sustain the alloimmune response after T-cell activation has already occurred. Targeting these cells provides a means for preventing or treating rejection.

The immune response against transplanted allografts is one of the most potent reactions mounted by the immune system. The acute rejection response has been attributed to donor dendritic cells (DCs), which migrate to recipient lymphoid tissues and directly activate alloreactive T cells against donor MHC molecules. Here, using a murine heart transplant model, we determined that only a small number of donor DCs reach lymphoid tissues and investigated how this limited population of donor DCs efficiently initiates the alloreactive T cell response that causes acute rejection. In our mouse model, efficient passage of donor MHC molecules to recipient conventional DCs (cDCs) was dependent on the transfer of extracellular vesicles (EVs) from donor DCs that migrated from the graft to lymphoid tissues. These EVs shared characteristics with exosomes and were internalized or remained attached to the recipient cDCs. Recipient cDCs that acquired exosomes became activated and triggered full activation of alloreactive T cells. Depletion of recipient cDCs after cardiac transplantation drastically decreased presentation of donor MHC molecules to directly alloreactive T cells and delayed graft rejection in mice. These findings support a key role for transfer of donor EVs in the generation of allograft-targeting immune responses and suggest that interrupting this process has potential to dampen the immune response to allografts.

Cell proliferation is commonly assayed in the laboratory for research purposes, but is increasingly used clinically to gauge tumor aggressiveness and potentially guide care. Therefore, both researchers and clinicians should have a basic understanding of techniques used to assess cell proliferation. Multiple cell proliferation assays exist, and the choice of method depends on the laboratory resources available, the types of cells/tissues to be studied, and the specific experimental goals. In this article, we identify four overarching categories of cell proliferation assays that signify various stages of the cell cycle: nucleoside-analog incorporation, cell cycle-associated protein detection, use of cytoplasmic proliferation dyes, and indirect measures of cell proliferation. Each method has strengths and limitations that should guide the dermatology investigator's choice of assay., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Pustular psoriasis is an uncommon psoriasis variant, clinically characterized as small sterile pustules on an erythematous base. Evidence for therapy is lacking, and many currently employed systemic therapeutics carry risks of significant side effects, without specifically targeting disease etiology which includes the aggregation of neutrophils., Observations: We report therapy with the anti-neutrophil agent dapsone in 5 patients with pustular psoriasis and provide a brief review of the literature. Four patients responded to oral dapsone and 1 to topical dapsone therapy. All 5 patients had previously failed multiple topical and systemic treatments. In 2 cases, oral dapsone allowed for the discontinuation of other systemic agents. One patient stopped oral dapsone due to a side effect of sleep disturbance., Conclusion: Dapsone has a much safer side effect profile and may target the pathophysiology of pustular psoriasis more directly than many other systemic agents. As such, dapsone should be considered for the treatment of patients with pustular psoriasis., (© 2015 S. Karger AG, Basel.)

Increasing evidence indicates the existence of a complex cross-regulation between the most important biosensors of the human body: The immune and nervous systems. Cytokines control body temperature and trigger autoimmune disorders in the central nervous system, whereas neuropeptides released in peripheral tissues and lymphoid organs modulate inflammatory (innate) and adaptive immune responses. Surprisingly, the effects of nerve fibers and the antidromic release of its pro-inflammatory neuropeptides on the leukocytes of the immune system that mediate graft rejection are practically unknown. In the transplantation field, such area of research remains practically unexplored. A recent study by Riol-Blanco et al has revealed new details on how nociceptive nerves regulate the pro-inflammatory function of leukocytes in peripheral tissues. Although the mechanism(s) by which neuroinflammation affects the immune response against the allograft remains unknown, recent data suggest that this new area of research is worth exploring for potential development of novel complementary therapies for prevention/treatment of graft rejection., (© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Pemphigus vulgaris is an uncommon intraepidermal blistering disorder that typically presents with flaccid bullae or erosions. We report a patient with pemphigus vulgaris who presented with several unusual clinical features: tense bullae with dependently layered pus, true target lesions coalescing into annular configurations, and diffuse desquamation that initially raised concern for toxic epidermal necrolysis. We discuss the differential diagnosis and implications of these morphological findings.

Although chlorhexidine gluconate (CHG) disks have been shown to help reduce the incidence of central line-associated blood stream infections, their use can result in local skin necrosis. The effects of CHG disks on patients with complex skin pathology have not been studied. We report 6 cases of dermal necrosis associated with Biopatch (Ethicon Inc, Somerville, NJ) CHG disks in adults with complex skin pathology including those with Stevens-Johnson syndrome, toxic epidermal necrolysis syndrome, graft-versus-host disease, burns, and anasarca. All patients had a CHG disk placed at a central venous catheter insertion site. Age range was from 21 to 84 years. Discovery of the reaction ranged from 4 to 14 days after disk placement. Resultant skin erosions required 2 to 10 weeks to reepithelialize. Complicated skin disorder patients represent a rare subset of the critically ill who appear prone to CHG disk necrosis. Continuous contact of CHG under occlusive dressings is speculated to predispose Stevens-Johnson syndrome, toxic epidermal necrolysis syndrome, graft-versus-host disease, and burn patients to local chemical injury secondary to loss of the epithelial tissue barrier, decreased cohesion of the epidermal-dermal junction, and increased tissue permeability. In these patients, the risk of placing the CHG disk may present more risk than using alternative antimicrobial dressings., (Published by Elsevier Inc.)

Alopecia areata is an immune-mediated, nonscarring form of hair loss. A new study using human clinical samples and a mouse model demonstrates that CD8αβ⁺NKG2D⁺ T effector memory cells mediate alopecia areata in part through Janus kinase (JAK) signaling and that alopecia areata might be treated with JAK inhibitors.

A critical goal in transplantation is the achievement of donor-specific tolerance, minimizing the use of immunosuppressants. Dendritic cells (DCs) are antigen (Ag) presenting cells (APCs) with capability to promote immunity or tolerance. The immune-regulatory properties of DCs have been exploited for generation of tolerogenic/immunosuppressive (IS) DCs that, when transfer systemically, prolong allograft survival in murine models. Surprisingly, the in vivo mechanisms of therapies based on (donor- or recipient-derived) ISDCs in transplantation remain unknown, given that previous studies investigated their effects in vitro, or ex vivo after transplantation. Since once injected, ISDCs are short-lived and transfer Ag to recipient APCs, we assessed the role of recipient DCs by depleting them at the time of ISDC-therapy in a mouse model of cardiac transplantation. The results indicate that, contrary to the accepted paradigm, systemically administered ISDCs reduce the alloresponse and prolong allograft survival, not by themselves, but through conventional DCs (cDCs) of the recipient. These findings raise doubts on the advantages of the currently used ISDC-therapies, since the immune-regulatory properties of the injected ISDC do not seem to be functionally relevant in vivo, and the quiescent/pro-tolerogenic status of cDCs may be compromised in patients with end-stage diseases that require transplantation., (© Copyright 2012 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: Reliable prognostic biomarkers of survival and response to treatment are clearly important in oncology, and many studies have been carried out with the objective of identifying new prognostic biomarkers. Retrospective analysis of blood banked from patients is a frequently used paradigm for these studies. We describe a new study of the association of serum biomarker level with overall survival in melanoma patients, and the problems encountered in carrying it out., Methods: Blood samples from 56 patients with stage IV metastatic melanoma were drawn prior to initiation of any treatment for their disease. Sera from the samples were stored for up to 94 months at -80°C, and were subsequently thawed at the same time and tested by multiplex Luminex assay for 30 analytes (cytokines, chemokines and growth factors). Cox regression analysis was used to assess the association between these analytes and time-to-death., Results: Of the 30 analytes, 17 were associated with survival, most strongly so, and in all cases, a higher analyte level was associated with increased survival. In addition, the correlations of the levels of all possible pairs of analytes were all positive and in almost all cases highly significant. However, these results are artifacts that arise from the combination of two peculiarities of the data: the apparent decrease in analyte level with storage time, and the uniformly shorter storage times of the samples from censored patients than the storage times of the samples from patients who died., Conclusions: All retrospective studies can have hidden biases, and thus investigators should not claim new findings before examining the data in detail with the goal of determining whether the findings could be spurious. There were several suspicious findings in our initial analyses: too many analytes found significant, too many very small p-values, a uniformly positive association of analyte level with survival, and a uniformly positive correlation between analyte levels. We were convinced that these findings must be artifacts, and further analyses showed that the findings could be explained by an apparent decrease of analyte level storage time., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Dendritic cells (DCs) are the most potent APCs. Whereas immature DCs down-regulate T-cell responses to induce/maintain immunologic tolerance, mature DCs promote immunity. To amplify their functions, DCs communicate with neighboring DCs through soluble mediators, cell-to-cell contact, and vesicle exchange. Transfer of nanovesicles (< 100 nm) derived from the endocytic pathway (termed exosomes) represents a novel mechanism of DC-to-DC communication. The facts that exosomes contain exosome-shuttle miRNAs and DC functions can be regulated by exogenous miRNAs, suggest that DC-to-DC interactions could be mediated through exosome-shuttle miRNAs, a hypothesis that remains to be tested. Importantly, the mechanism of transfer of exosome-shuttle miRNAs from the exosome lumen to the cytosol of target cells is unknown. Here, we demonstrate that DCs release exosomes with different miRNAs depending on the maturation of the DCs. By visualizing spontaneous transfer of exosomes between DCs, we demonstrate that exosomes fused with the target DCs, the latter followed by release of the exosome content into the DC cytosol. Importantly, exosome-shuttle miRNAs are functional, because they repress target mRNAs of acceptor DCs. Our findings unveil a mechanism of transfer of exosome-shuttle miRNAs between DCs and its role as a means of communication and posttranscriptional regulation between DCs.

To fulfill its immunologic functions, the skin is richly populated with dendritic cells (DCs), the most potent professional Ag-processing and Ag-presenting cells of the immune system. The immune-stimulatory and tolerogenic functions of skin DCs are regulated by the immune and neuroendocrine systems. Pro-inflammatory neuropeptides like substance P and calcitonin gene-related peptide secreted by cutaneous Aδ and C nerve fibers are the main initiators of neuro-inflammatory responses in the skin. Conversely, anti-inflammatory neuropeptides like the products of cleavage of proopiomelanocortin (α-melanocyte-stimulating hormone and adrenocorticotropic hormone) negatively regulate immune responses in the skin. Likewise, the control of immune responses against stimuli applied to the skin depends on the balance between the release and neutralization of pro-inflammatory and anti-inflammatory neuropeptides, a matter that has been somehow overlooked by the immunology field until recently.

Malignant melanoma kills more people each year than any other skin cancer, with approximately 8000 lives lost and a cost of over 3 billion dollars annually in the US alone. Tumor depth is the most important prognostic factor in melanoma. Thus, early detection has the potential to diagnose melanoma when lesions are thinner, and to improve survival in primary melanomas. In this review, we discuss the implications, barriers, and advantages of melanoma screening, and describe the currently employed methods of detection, newly available modalities, and current areas of research. We also discuss the efficacy, advantages and disadvantages, and clinical practicality of each, and suggest various means of combining different methodologies as well as tailoring various strategies to individual patient needs.

The prevailing idea regarding the mechanism(s) by which therapeutic immunosuppressive dendritic cells (DCs) restrain alloimmunity is based on the concept that they interact directly with antidonor T cells, inducing anergy, deletion, and/or regulation. However, this idea has not been tested in vivo. Using prototypic in vitro-generated maturation-resistant (MR) DCs, we demonstrate that once MR-DCs carrying donor antigen (Ag) are administered intravenously, they decrease the direct and indirect pathway T-cell responses and prolong heart allograft survival but fail to directly regulate T cells in vivo. Rather, injected MR-DCs are short-lived and reprocessed by recipient DCs for presentation to indirect pathway CD4(+) T cells, resulting in abortive activation and deletion without detrimental effect on the number of indirect CD4(+) FoxP3(+) T cells, thus increasing the regulatory to effector T cell relative percentage. The effect on the antidonor response was independent of the method used to generate therapeutic DCs or their viability; and in accordance with the idea that recipient Ag-presenting cells mediate the effects of therapeutic DCs in transplantation, prolongation of allograft survival was achieved using donor apoptotic MR-DCs or those lacking surface major histocompatibility complex molecules. We therefore conclude that therapeutic DCs function as Ag-transporting cells rather than Ag-presenting cells to prolong allograft survival.

PURPOSE. Interleukin (IL)-12p40 can couple with IL-12p35 or p19 chains to form the molecules IL-12p70 and IL-23, respectively, which promote T(H)1 cytokine responses. IL-12p35 can bind to EBI3 to form the anti-inflammatory molecule IL-35, but a proinflammatory function of IL-12p35 independent of IL-12p40 has not been described. Here such a function in a mouse model of herpes stromal keratitis (HSK), a CD4(+) T(H)1 cell-dependent corneal inflammation, is demonstrated. METHODS. Corneas of wild-type (WT), IL-12p40(-/-), IL-12p35(-/-), and IL-12p35(-/-)p40(-/-) (double knockout) mice were infected with the RE strain of HSV-1, and HSK was monitored based on corneal opacity, neovascularization, leukocytic infiltrate, and cytokine/chemokine levels. RESULTS. All mouse strains developed moderate HSK by 11 days after infection (dpi). However, from 11 to 21 dpi, HSK progressed in WT and IL-12p40(-/-) mice but regressed in IL-12p35(-/-) and IL-12p35(-/-)p40(-/-) mice. HSK regression was characterized by reductions in neutrophils and CD4(+) T cells and attenuation of blood vessels, which was associated with reduced levels of the chemokines KC (CXCL3), Mip-2 (CXCL2), and MCP-1 (CCL2) and the angiogenic factor vascular endothelial growth factor. CONCLUSIONS. HSK development does not require IL-12p40 and is thus independent of IL-12p70 and IL-23. However, late HSK progression does require a previously unrecognized IL-12p40-independent, proinflammatory function of IL-12p35.

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease that targets the beta-cells of the pancreas. We investigated the ability of soluble galectin-1 (gal-1), an endogenous lectin that promotes T cell apoptosis, to down-regulate the T cell response that destroys the pancreatic beta-cells. We demonstrated that in nonobese diabetic (NOD) mice, gal-1 therapy reduces significantly the amount of Th1 cells, augments the number of T cells secreting IL-4 or IL-10 specific for islet cell Ag, and causes peripheral deletion of beta-cell-reactive T cells. Administration of gal-1 prevented the onset of hyperglycemia in NOD mice at early and subclinical stages of T1D. Preventive gal-1 therapy shifted the composition of the insulitis into an infiltrate that did not invade the islets and that contained a significantly reduced number of Th1 cells and a higher percentage of CD4(+) T cells with content of IL-4, IL-5, or IL-10. The beneficial effects of gal-1 correlated with the ability of the lectin to trigger apoptosis of the T cell subsets that cause beta-cell damage while sparing naive T cells, Th2 lymphocytes, and regulatory T cells in NOD mice. Importantly, gal-1 reversed beta-cell autoimmunity and hyperglycemia in NOD mice with ongoing T1D. Because gal-1 therapy did not cause major side effects or beta-cell toxicity in NOD mice, the use of gal-1 to control beta-cell autoimmunity represents a novel alternative for treatment of subclinical or ongoing T1D.

Chronic allograft vasculopathy (CAV) is an atheromatous-like lesion that affects vessels of transplanted organs. It is a component of chronic rejection that conventional immuno-suppression fails to prevent, and is a major cause of graft loss. Indirect allo-recognition through T cells and allo-Abs are critical during CAV pathogenesis. We tested whether the indirect allo-response and its impact on CAV is down-regulated by in situ-delivery of donor Ags to recipient's dendritic cells (DCs) in lymphoid organs in a pro-tolerogenic fashion, through administration of donor splenocytes undergoing early apoptosis. Following systemic injection, donor apoptotic cells were internalized by splenic CD11c(hi) CD8alpha(+) and CD8(-) DCs, but not by CD11c(int) plasmacytoid DCs. Those DCs that phagocytosed apoptotic cells in vivo remained quiescent, resisted ex vivo-maturation, and presented allo-Ag for up to 3 days. Administration of donor apoptotic splenocytes, unlike cells alive, (i) promoted deletion, FoxP3 expression and IL-10 secretion, and decreased IFN-gamma-release in indirect pathway CD4 T cells; and (ii) reduced cross-priming of anti-donor CD8 T cells in vivo. Targeting recipient's DCs with donor apoptotic cells reduced significantly CAV in a fully-mismatched aortic allograft model. The effect was donor specific, dependent on the physical characteristics of the apoptotic cells, and was associated to down-regulation of the indirect type-1 T cell allo-response and secretion of allo-Abs, when compared to recipients treated with donor cells alive or necrotic. Down-regulation of indirect allo-recognition through in situ-delivery of donor-Ag to recipient's quiescent DCs constitutes a promising strategy to prevent/ameliorate indirect allorecognition and CAV.

Purpose: To investigate herpes stromal keratitis (HSK) immunopathology by studying HSV-1-infected corneas that fail to develop HSK., Methods: Plaque assay quantified HSV-1 in the tear film of infected mice. FACS analysis enumerated corneal leukocytic infiltrate and characterized infiltrate phenotypically after staining for activation and regulatory T cell (Treg) markers and for markers of antigen-presenting cell (APC) maturation. Treg cells were depleted in vivo using anti-CD25 mAb. Luminex analysis quantified the amount of cytokines and chemokines expressed in corneal tissue homogenate., Results: Infected corneas without HSK exhibited a pronounced leukocytic infiltrate containing a significantly higher proportion and nearly identical absolute number of activated CD4+ T cells 15 days after infection when compared with those with HSK. Moreover, the frequency and absolute number of regulatory CD4+ T cells (Tregs) was lower in nondiseased corneas, and Treg depletion did not influence HSK incidence. The frequency of mature, immunogenic DCs and the ratio of mature DCs to CD4+ T cells were nearly identical in corneas with and without HSK. The authors observed a reduced population of neutrophils and reduced expression of neutrophil chemoattractants MIP-1beta and keratinocyte chemoattractant and the neutrophil-attracting cytokine IL-6 in corneas without HSK., Conclusions: These findings demonstrate that HSV-1-infected corneas can retain clarity in the presence of a substantial secondary leukocytic infiltrate, that activated CD4+ T cells, while necessary, are not sufficient for HSK development, that susceptibility to HSK is not determined by Tregs, and that clinical disease correlates with the accumulation of a critical mass of neutrophils through chemoattraction.

Exosomes are nanovesicles released by different cell types including dendritic cells (DCs). The fact that exosomes express surface MHC-peptide complexes suggests that they could function as Ag-presenting vesicles or as vehicles to spread allogeneic Ags for priming of anti-donor T cells during elicitation of graft rejection or induction/maintenance of transplant tolerance. We demonstrate that circulating exosomes transporting alloantigens are captured by splenic DCs of different lineages. Internalization of host-derived exosomes transporting allopeptides by splenic DCs leads to activation of anti-donor CD4 T cells by the indirect pathway of allorecognition, a phenomenon that requires DC-derived, instead of exosome-derived, MHC class II molecules. By contrast, allogeneic exosomes are unable to stimulate direct-pathway T cells in vivo. We demonstrate in mice that although graft-infiltrating leukocytes release exosomes ex vivo, they do not secrete enough concentrations of exosomes into circulation to stimulate donor-reactive T cells in secondary lymphoid organs. Instead, our findings indicate that migrating DCs (generated in vitro or isolated from allografts), once they home in the spleen, they transfer exosomes expressing the reporter marker GFP to spleen-resident DCs. Our results suggest that exchange of exosomes between DCs in lymphoid organs might constitute a potential mechanism by which passenger leukocytes transfer alloantigens to recipient's APCs and amplify generation of donor-reactive T cells following transplantation.

Several studies have provided evidence that interleukin-15 (IL-15) can enhance protective immune responses against Mycobacterium tuberculosis infection. However, the effects of IL-15 deficiency on the functionality of M. tuberculosis-specific CD4 and CD8 T cells are unknown. In this study, we investigated the generation and maintenance of effector and memory T-cell responses following M. tuberculosis infection of IL-15(-/-) mice. IL-15(-/-) mice had slightly higher bacterial numbers during chronic infection, which were accompanied by an increase in gamma interferon (IFN-gamma)-producing CD4 and CD8 T cells. There was no evidence of increased apoptosis or a defect in proliferation of CD8 effector T cells following M. tuberculosis infection. The induction of cytotoxic and IFN-gamma CD8 T-cell responses was normal in the absence of IL-15 signaling. The infiltration of CD4 and CD8 T cells into the lungs of "immune" IL-15(-/-) mice was delayed in response to M. tuberculosis challenge. These findings demonstrate that efficient effector CD4 and CD8 T cells can be developed following M. tuberculosis infection in the absence of IL-15 but that recall T-cell responses may be impaired.