Update on pathobiology in Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrosis (TEN) are rare but life-threatening severe cutaneous adverse reactions (SCARs), which are mainly induced by a variety of drugs. Once considered to be unpredictable, significant progress has been achieved in understanding the pathological mechanisms underlying such reactions. Recent studies suggested that SJS/TEN is a specific immune reaction where human leukocyte antigen (HLA) alleles specific for certain drugs in defined populations are involved in the activation of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Upon the activation, various cytotoxic and immunological signals, including but not limited to Fas/Fas ligand, perforin/granzyme B, and granulysin are launched to mediate the disseminated keratinocyte death in SJS/TEN. This review provides an update on the pathobiology of SJS/TEN in both the genomic and immunologic perspectives. The knowledge gained from these cutting-edge studies will form the basis for better prevention and management of SJS/TEN.     

Diagnosis and management of Stevens-Johnson syndrome/toxic epidermal necrolysis

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a rare, immunologically mediated cutaneous adverse reaction characterized by mucous membrane and epidermal detachment, with a mortality ranging from 15% to 25%. Risk factors for the development of SJS/TEN include immune dysregulation, active malignancy, and genetic predisposition. Medications are the most common cause, particularly antimicrobials, antiepileptics, allopurinol, and nonsteroidal anti-inflammatory medications. Drug-specific CD8 T-cells and natural killer cells are thought to be the major inducers of keratinocyte apoptosis via release of soluble cytotoxic mediators, including Fas ligand, perforin/granzyme, tumor necrosis factor, and granulysin. When SJS/TEN is suspected clinically, appropriate therapy should be instituted without delay. All patients should be managed initially in an intensive care unit or burn unit under a multidisciplinary team of physicians experienced in the care of patients with SJS/TEN. Available data support the use of various pharmacologic agents to halt disease progression and improve outcomes, but no single drug has been found to be superior or beneficial for all patients. Future research should focus on developing a better understanding of the genetic susceptibility and immunopathophysiology of the disease, as well as novel diagnostic and therapeutic targets to improve patient outcomes.     

Recent advances in the genetics and immunology of Stevens-Johnson syndrome and toxic epidermal necrosis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrosis (TEN) are rare but life-threatening severe cutaneous adverse reactions (SCARs), which are majorly (65-75%) induced by a variety of drugs. SJS/TEN could be recognized as SCARs or drug immune reactions, if the reactions are elicited by drugs. The recent studies suggested that SJS/TEN is a specific immune reaction initiated by the cytotoxic T lymphocytes (CTLs) via human leukocyte antigens (HLAs)-restricted pathway. The patho-mechanism involving HLA-restricted presentation of a drug or its metabolites for T-cell activation is supported by the findings of strong genetic associations with HLA alleles (e.g. HLA-B*15:02 and carbamazepine-SJS/TEN, and HLA-B*58:01 and allopurinol-SJS/TEN). However, the genetic associations of SJS/TEN or drug induced cutaneous immune reactions are complex, which are drug specific and ethnicity specific. The genetic polymorphisms and diversity of HLA alleles may provide different binding affinities for drug antigens to launch the activation of specific CTLs responses, further leading to the unique clinical manifestations in SJS/TEN. Fas-FasL and perforin/granzyme B have been advocated mediating the epidermal necrosis in SJS/TEN. Our recent study showed that granulysin, a cytotoxic protein produced by CTLs or natural killer (NK) cells, is the key mediator for disseminated keratinocyte death in SJS/TEN. From the point of view of a physician, the profounder understanding of the genetic predisposition and patho-mechanism we discover, the better strategies for prevention, clinical management, and therapeutic methods of SJS/TEN we can develop in the near future.     

Critical factors differentiating erythema multiforme majus from Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN)

Erythema multiforme majus (EMM) and Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) are severe cutaneous reactions characterised by targetoid erythematous lesions and mucocutaneous involvement. The initial skin manifestations are similar, making early diagnosis difficult. We retrospectively reviewed 36 cases of EMM and 18 cases of SJS/TEN and also evaluated 6 patients with unclassified EMM. 13 patients in the EMM group and 16 patients in the SJS/TEN group presented with a high fever (>38.5?C; p<0.001). Two or more mucous membranes were affected in 6 patients in the EMM group and 18 patients in the SJS/TEN group. Significantly more SJS/TEN than EMM patients had high levels of C-reactive protein and severe hepatic dysfunction. Thirteen EMM and 13 SJS/TEN cases were caused by medications/drugs. Skin biopsy samples showed stronger mononuclear cell infiltration in the EMM than in the SJS/TEN group (p<0.001). The mean dose of initial systemic corticosteroid used to treat EMM was lower than that used to treat SJS/TEN. No patients died in either group. Clinically, the unclassified cases mostly behaved like EMM. The results of our investigation suggest that EMM and SJS/TEN are distinct conditions and they help in differentiating these syndromes at an early stage.     

Epidermal necrolysis: 60 years of errors and advances

Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare conditions characterized by extensive epidermal detachment and mucositis. Both are associated with a high mortality rate and significant long‐term morbidity. Since the initial report introducing the term TEN in 1956, diagnosis of the condition has been fraught with difficulties that continue to exist today. The terms ‘erythema multiforme major’ (EMM) and SJS, and their relationship to TEN have also been confusing to clinicians. It is now recognized that EMM is a different entity from SJS and TEN in terms of demographics, causality and severity. SJS and TEN represent a continuum of disease, and differ only by the extent of epidermal detachment and therefore severity. The term ‘epidermal necrolysis’ (EN) is used in this article to describe the spectrum of disease that includes SJS and TEN. Important advances in understanding the pathomechanism and treatment of EN have been made over the years. These include the recognition of human leucocyte antigen (HLA) associations (e.g. HLA‐B*1502 with carbamazepine‐induced TEN) and understanding of the pathogenic roles of drug‐specific cytotoxic T cells and granulysin. It was previously believed that widespread keratinocyte death in EN is predominantly mediated by soluble Fas‐ligand and that intravenous immunoglobulin therapy is useful in blocking this mechanism with resultant survival benefits. Further studies have since proven these theories to be incorrect. This short review describes the key advances in the terminology, classification, causality and treatment of EN, and identifies future priorities and challenges in the understanding and management of this condition.     

Severe cutaneous adverse drug reactions

The clinical manifestations of drug eruptions can range from mild maculopapular exanthema to severe cutaneous adverse drug reactions (SCAR), including drug‐induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms, Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) which are rare but occasionally fatal. Some pathogens may induce skin reactions mimicking SCAR. There are several models to explain the interaction of human leukocyte antigen (HLA), drug and T‐cell receptor (TCR): (i) the “hapten/prohapten” theory; (ii) the “p‐i concept”; (iii) the “altered peptide repertoire”; and (iv) the “altered TCR repertoire”. The checkpoints of molecular mechanisms of SCAR include specific drug antigens interacting with the specific HLA loci (e.g. HLA‐B*15:02 for carbamazepine‐induced SJS/TEN and HLA‐B*58:01 for allopurinol‐induced SCAR), involvement of specific TCR, induction of T‐cell‐mediated responses (e.g. granulysin, Fas ligand, perforin/granzyme B and T‐helper 1/2‐associated cytokines) and cell death mechanism (e.g. miR‐18a‐5p‐induced apoptosis; annexin A1 and formyl peptide receptor 1‐induced necroptosis in keratinocytes). In addition to immune mechanism, metabolism has been found to play a role in the pathogenesis of SCAR, such as recent findings of strong association of CYP2C9*3 with phenytoin‐induced SCAR and impaired renal function with allopurinol SCAR. With a better understanding of the mechanisms, effective therapeutics and prevention for SCAR can be improved.     

Cytotoxic granules in distinct subsets of cutaneous lupus erythematosus

In cutaneous lupus erythematosus (CLE), the pathogenetic role of cytotoxic granules has been demonstrated in the subacute and discoid subtypes, which show interface dermatitis, but little is known about tumid (T)CLE, which does not show this interface dermatitis, and evolves with minimal epidermal changes. We studied cytotoxic T lymphocytes and cytotoxic granules in discoid (n = 21), subacute (n = 17), and tumid (n = 21) CLE samples. Skin sections were immunohistochemically stained for CD8, CD56, perforin, granzyme A, granzyme B, and granulysin. Inflammatory cells containing the four subtypes of cytotoxic granules were found in all the three CLE forms; however, only the TCLE group showed a positive correlation between the density of CD8+ cells and each subtype of cytotoxic granule‐positive cells. In addition, only the TCLE group showed synergy between the densities of cells containing cytotoxic granule subtypes. Cytotoxic granules are important in the pathomechanism of TCLE. They may perform functions other than apoptosis, including maintenance of inflammation and dermal mucinous deposits in TCLE.     

Open trial of ciclosporin treatment for Stevens–Johnson syndrome and toxic epidermal necrolysis

Background Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are acute mucocutaneous reactions associated with poor prognosis. The treatment is mainly symptomatic, based on supportive care. Until now, several curative treatments have been proposed without evidence of effectiveness. Objectives To evaluate the effect of ciclosporin on SJS and TEN after a short series had suggested a benefit. Methods We conducted an open, phase II trial to determine the safety and possible benefit of ciclosporin. Among the 45 consecutive patients admitted for SJS/TEN from March 2005 to September 2007, 29 fulfilled inclusion criteria. Ciclosporin was administered orally (3 mg kg^?1 daily for 10 days) and tapered over a month. Clinical and biological evaluations were performed sequentially. Predicted death rate was estimated with a validated prognostic score (SCORTEN). Results Twenty‐nine patients were included at a mean ± SD of 2·8 ± 1·8 days after onset. The final diagnosis was SJS (n = 10), SJS/TEN overlap (n = 12) and TEN (n = 7). One month of treatment was completed in 26. Ciclosporin was stopped after more than 10 days in three cases for side‐effects including posterior leucoencephalopathy (n = 1), neutropenia (n = 1) and nosocomial pneumopathy (n = 1). Ciclosporin dosage was tapered earlier than scheduled in two cases for alteration in renal function. The prognostic score predicted 2·75 deaths; none occurred (P = 0·1). Mean epidermal detachment remained stable in 18 of 29 cases (62%). The mean ± SD hospital stay was 16·2 ± 9·1 days. Conclusions Both the death rate and the progression of detachment seemed lower than expected, suggesting a possible usefulness of ciclosporin in SJS and TEN that needs to be confirmed.     

Endothelial cell apoptosis in severe drug‐induced bullous eruptions

Background Toxic epidermal necrolysis (TEN) and Stevens–Johnson syndrome (SJS) are characterized by extensive keratinocyte apoptosis mediated by cytotoxic proteins. Similar features have been found in another severe dysimmune syndrome, allogeneic acute graft‐versus‐host disease, where endothelial cell apoptosis has been recently characterized. Objectives To determine whether endothelial cell apoptosis occurs in dermal vessels of TEN and SJS, and whether it is linked to expression of cytotoxic proteins. Methods Skin biopsies of eight patients with severe drug‐induced bullous eruptions (four TEN, four SJS), eight with drug‐induced urticaria and eight healthy controls were compared. Blood vessel damage was studied by electron microscopy and quantified by CD31 immunostaining. Apoptotic cells, characterized by electron microscopy, were quantified on terminal deoxyribonucleotidyl transferase‐mediated deoxyuridine triphosphate nick end labelling assay. Immunohistochemistry was also used to characterize and quantify inflammatory cells and granzyme B, tumour necrosis factor (TNF)‐α and Fas ligand (FasL) expression. Results Endothelial cell apoptosis was observed in all TEN and SJS cases: it occurred in 85% of the vessel sections. It occurred in one case of drug‐induced urticaria, in 5% of vessel sections, but not in healthy controls. Numbers of CD68+ macrophages and CD8+ T lymphocytes were significantly higher in TEN and SJS compared with both other groups; granzyme B and TNF‐α but not FasL were expressed. Conclusions Characterization of endothelial cell apoptosis in TEN and SJS is important to assess a factor worsening skin damage, with possible extension to other organs. It may also be useful for the development of novel therapeutic strategies.     

The role of perforin-mediated apoptosis in lichen planus lesions

Lichen planus is recognized as a T-cell-mediated disease. Histologically, it is characterized by the formation of colloid bodies representing apoptotic keratinocytes. The apoptotic process mediated by CD8⁺ cytotoxic T lymphocytes (CTLs) and NK cells mainly involves two distinct pathways: the perforin/granzyme pathway and the Fas/FasL pathway. So far, little is known regarding the role of perforin-mediated apoptosis in lichen planus. In the present study, the expression and distribution of perforin, T and NK cell subsets in the epidermis and dermis of lesional and nonlesional lichen planus skin were studied. Skin biopsy specimens from lesional and nonlesional skin of ten patients with lichen planus and eight healthy persons were analysed by immunohistochemistry. Significant accumulation of T cells, particularly of CD4⁺ and CD8⁺ subsets, was found in both epidermis and dermis of lichen planus lesions compared with nonlesional and healthy skin. There were no significant differences in the incidence of NK cells (CD16⁺ and CD56⁺) between lesional, nonlesional and healthy skin. Perforin expression was significantly upregulated in the epidermis of lichen planus lesions. In conclusion, accumulation of perforin⁺ cells in the epidermis of lichen planus lesions suggest a potential role of perforin in the apoptosis of basal keratinocytes.     

颗粒溶素在皮肤病中的研究进展

颗粒溶素是一种溶细胞和促炎症分子,表达于活化的人类细胞毒T细胞(CTLs)和自然杀伤(NK)细胞,参与Stevens-Johnson综合征/中毒性坏死性表皮松解症(SJS/TEN)、银屑病、毛囊炎、扁平苔藓和病毒性水疱等多种皮肤病的发生发展,尤其在SJS/TEN发病过程中是引起角质形成细胞凋亡的重要诱导物。本文就颗粒溶素在皮肤病早期诊断、病情监测及治疗中的应用作一综述。     

Animal models of toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe acute exfoliative skin diseases developing extensive epidermal detachment and mucosal damage. Although SJS and TEN are mostly caused by drugs, an animal model of TEN using drugs has not been established yet. We have established an autoimmune skin disease model mouse reproducing the devastating skin damage of TEN by a combination of transgenic mice expressing an epidermal model antigen and its specific CD8(+) T-cell receptor. In this model mouse, we found that the thymus-derived CD4(+) CD25(+) regulatory T cell (Treg) is a critical regulator of cytotoxic T lymphocytes (CTL) causing TEN. Indeed, loss of Treg function was recently demonstrated by human studies of TEN patients. Although how drug-reactive CTL is activated in vivo is still unknown, this model elucidated the immunological pathomechanism of TEN after CTL obtained cytotoxicity against epidermal keratinocyte. In this review, roles of CTL, Treg, cytotoxic granules and antigen-presenting cells were discussed on pathogenesis of TEN.     

Balance of Treg versus T‐effector cells during systemic treatment with adalimumab and topical treatment with calcipotriol–betamethasone dipropionate ointment

Diminished suppressive capacity of regulatory T cells (Treg) has been demonstrated in blood and in lesional skin of psoriatic patients. Treatment with anti‐TNFα restored the number and function of circulating Treg in psoriasis. We aimed to study Treg in the skin of psoriatic patients undergoing topical treatment with calcipotriol–betamethasone dipropionate (CBD) ointment (n = 12) or systemic treatment with anti‐TNFα agent adalimumab (n = 10). Skin biopsies were collected from patients with chronic plaque psoriasis who responded to the above‐mentioned treatments with a SUM‐score improvement of at least 50% (at the end of treatment). Biopsies were processed for immunohistochemistry. As Treg function is associated with a numerical balance between Treg and effector T cells, Foxp3/CD4 ratios were calculated. It appeared that both treatments cause a significant decrease in the presence of Foxp3+ cells. However, in patients that were treated with CBD ointment, we observed lower Foxp3/CD4 ratios after 8 weeks of treatment compared to baseline (t = 0: 0.41 ± 0.08; t = 8: 0.22 ± 0.04, P = 0.033), whereas in patients who were treated with adalimumab we observed an increase of the Foxp3/CD4 ratios after 1.5 and 16 weeks of treatment compared to baseline (t = 0: 0.25 ± 0.04; t = 1.5: 0.32 ± 0.06; t = 16: 0.49 ± 0.10, P = 0.15). Based on Foxp3/CD4 ratios, we can conclude that adalimumab treated skin differs from CBD treated skin with regard to the anti‐inflammatory/inflammatory balance. We suggest that, in contrast to CBD ointment, adalimumab favours local Treg function in the skin.     

Stevens‐Johnson syndrome and toxic epidermal necrolysis associated with the use of macrolide antibiotics: a review of published cases

Macrolides are one of the most commonly prescribed antibiotics. In several studies, their use was associated with the occurrence of Stevens‐Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). This review aimed to explore and summarize available cases of SJS/TEN suspected to be associated with the use of macrolide antibiotics reported in the literature. Electronic searches were conducted in PubMed/MEDLINE, Web of Science, Scopus, and Serbian Citation Index (SCIndeks). Twenty‐five publications describing a total of 27 patients were included. Cases of SJS/TEN which satisfied inclusion criteria were found for azithromycin (n = 11), clarithromycin (n = 7), erythromycin (n = 5), roxithromycin (n = 2), and telithromycin (n = 2). The age of the patients ranged from 2 to 77 years (median: 29 years). There were 14 female (51.9%) and 13 male (48.1%) patients. SJS was diagnosed in 16 patients (59.3%), TEN in 10 patients (37.0%), and SJS/TEN overlap in one patient (3.7%). Time to onset of the first symptoms ranged from 1 to 14 days (median: 3 days). All patients received some form of supportive and symptomatic care. Systemic corticosteroids were reported to be administered in 12 patients (44.4%) and intravenous immunoglobulin in five patients (18.5%). Three patients (11.1%) died. Considering that SJS/TEN is a severe and potentially life‐threatening reaction, physicians should be aware that they could be adverse effects of macrolide antibiotics and keep in mind that prompt recognition of SJS/TEN and discontinuation of the culprit drug in combination with supportive care is essential.     

Combination therapy of intravenous immunoglobulin and corticosteroid in the treatment of toxic epidermal necrolysis and Stevens–Johnson syndrome: a retrospective comparative study in China

Background Toxic epidermal necrolysis (TEN) and Stevens–Johnson Syndrome (SJS) are drug‐induced diseases with no well‐established treatments. The application of corticosteroid therapy is controversial. Intravenous immunoglobulin (IVIG) therapy is emerging as a promising new method for the treatment of these two diseases. The efficacy of combination therapy of IVIG and corticosteroid in the treatment of TEN/SJS has seldom been reported. Methods Sixty‐five consecutive patients with either TEN or SJS, admitted over a 14‐year period from January 1993 to October 2007, were treated with corticosteroid and analyzed retrospectively using SCORTEN, a severity‐of‐illness scoring system for TEN/SJS prognosis, to evaluate efficacy. For patients admitted after January 2001, additional therapy with a dose of 0.4 g/kg/day of IVIG for 5 days was applied. Results In the 45 patients with TEN treated without IVIG, 8.63 patients were expected to die based on the SCORTEN system, but 10 deaths were observed. Standardized mortality ratio (SMR) analysis [(Σobserved deaths/Σexpected deaths) × 100] suggested that patients with TEN treated with systemic corticosteroid were 16% more likely to die than those treated with routine therapy (SMR = 1.16; 95% confidence interval, 0.56–2.13). In the further study of combination therapy, 12 patients with TEN and eight patients with SJS were admitted. There were two deaths in the TEN group and one death in the SJS group, with 3.51 deaths expected on the basis of the SCORTEN system. SMR analysis showed that combination therapy had a tendency to reduce the mortality rate of TEN (SMR = 0.85; 95% confidence interval, 0.18–2.50). Nevertheless, in both the TEN and SJS groups, the difference in mortality rate between the two therapies was not statistically significant (P = 0.651 and P = 1, respectively). In patients with TEN, combination therapy also reduced significantly the time of arrested progression (P = 0.019) and the total hospitalization time (P = 0.043), but could not reduce the time to the tapering of corticosteroid (P = 0.96). In SJS patients, the times of arrested progression and hospitalization were also reduced significantly (P = 0.019 and P = 0.0475, respectively). Likewise, the time to the tapering of corticosteroid was not reduced (P = 0.122). Conclusion Combination therapy with corticosteroid and IVIG exhibited a tendency to reduce the mortality rate in comparison with the solo administration of corticosteroid. The decrease in the mortality rate, however, was not statistically significant. Combination therapy also arrested progression earlier and decreased the hospitalization time, meaning that the total dose of corticosteroid may be reduced. Combination therapy, however, did not lead to earlier tapering of corticosteroid. No severe adverse effects of IVIG were found during treatment.     

Decreased suppression of CD8+ and CD4+ T cells by peripheral regulatory T cells in generalized vitiligo due to reduced NFATC1 and FOXP3 proteins

Regulatory T cells (Tregs) are involved in the suppression of activated T cells in generalized vitiligo (GV). The study was aimed to investigate Tregs functional defects in Treg:CD8⁺ and Treg:CD4⁺ T cells' co-culture systems of 55 GV patients and 45 controls. CD8⁺ and CD4⁺ T-cell proliferation was assessed by BrdU assay; production of IL-10, TGF-β and IFN-γ cytokines was assessed by ELISA; and FOXP3, CD25, NFATC1 and CD44 proteins were measured by flow cytometry. Generalized vitiligo patients showed reduced suppression of CD8⁺ and CD4⁺ T cells (P = .0384, P = .0084), increased IFN-γ (P < .0001, P = .0019), decreased IL-10 and TGF-β (P < .0001) and decreased FOXP3, CD25 and NFATC1 proteins (P < .0001). Active vitiligo (AV) patients showed reduced suppression of CD8⁺ & CD4⁺ T cells (P = .006, P = .015), increased IFN-γ (P = .036, P = .045), decreased IL-10 (P = .009, P = .021), FOXP3 (P = .0244) and NFATC1 (P = .019). Severe GV (50%-75% VASI) patients showed reduced suppression of CD8⁺ and CD4⁺ T cells (P = .0003, P = .001), increased IFN-γ (P = .0029, P < .0001), decreased IL-10 (P = .0057, P = .0017), FOXP3 (P = .002) and NFATC1 (P = .0347). VASI score was positively correlated with the suppression of CD8⁺ and CD4⁺ T cells (P = .0006, P < .0001), IL-10 (P = .0096, P = .029), FOXP3 (P = .0008) and NFATC1 (P = .043), whereas it was negatively correlated with IFN-γ (P = .0029, P = .0017). Early age of onset patients' Tregs demonstrated decreased suppression of CD8⁺ and CD4⁺ T cells (P = .0156, P = .0074), decreased TGF-β (P = .0212, P = .0083) and NFATC1 (P = .0103). NFATC1 was positively correlated with FOXP3 in Tregs (P < .0001). Our results suggest impaired Tregs suppressive function in GV patients due to decreased NFATC1, FOXP3, CD25, IL-10 and TGF-β resulting into increased CD8⁺ and CD4⁺ T-cell proliferation and IFN-γ production. For the first time, decreased NFATC1 levels were correlated with decreased FOXP3, thereby altering Treg cell function in GV patients. Additionally, decreased Treg cell function also affected onset, activity and severity of GV.     

Procalcitonin as a diagnostic indicator for systemic bacterial infections in patients with Stevens–Johnson syndrome/toxic epidermal necrolysis

Elevated serum procalcitonin (PCT) level has been reported to be a diagnostic index in systemic bacterial infections, but it can also increase in some non‐infectious inflammatory diseases. Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) is a rare immune‐mediated cutaneous mucosal reaction which is susceptible to bacterial infections and may have elevated PCT levels. The value of serum PCT has not been assessed in series of SJS/TEN patients. We aimed to investigate the PCT levels in SJS/TEN patients with systemic bacterial infections (systemic infected group), with skin surface bacterial infections (skin surface infected group) and without infections (non‐infected group), to assess whether PCT was a valuable indicator for systemic bacterial infections in SJS/TEN patients. The PCT and C‐reactive protein (CRP) levels of 42 inpatients with SJS/TEN were retrospectively analysis. The receiver–operator curve (ROC) was used to determine the diagnostic efficacy of PCT for systemic bacterial infections in SJS/TEN patients. The results demonstrated that PCT levels in the systemic infected group were significantly higher than those in the other two groups (P < 0.05). There was no significant difference in CRP between the three groups. The cut‐off PCT level of 0.65 ng/mL calculated by ROC had optimal diagnostic efficacy, with sensitivity and specificity of 84.6% and 89.7%, respectively. PCT and severity‐of‐illness score for toxic epidermal necrolysis were positively correlated (P < 0.05). In conclusion, PCT is a valuable index and superior to CRP in detecting systemic bacterial infections in SJS/TEN patients. The level of PCT can partially reflect the severity of the disease.     

Death ligand TRAIL, secreted by CD1a+ and CD14+ cells in blister fluids, is involved in killing keratinocytes in toxic epidermal necrolysis

Toxic epidermal necrolysis (TEN) is characterized by an acute detachment and destruction of keratinocytes, affecting large areas of the skin. It is often related to adverse drug reactions. Previous studies have shown that effector CD8+ T cells, which accumulate in the blister fluid, are functionally cytotoxic and act through a classical perforin/granzyme B pathway. It has recently been shown that these cytotoxic T cells also secrete granulysin peptide, which is lethal to keratinocytes. These cytotoxic T cells exert their killer activity against autologous keratinocytes in the presence of the drug. However, they are unlikely to be the only effectors of TEN. We therefore searched for soluble death factors in the blister fluids that might kill keratinocytes. We found that the amounts of interferon-γ, TRAIL and TNF-α proteins were significantly greater in TEN blister fluids than in all controls (normal sera, TEN sera, burns and Eosinophilic pustular folliculitis blister fluids) and TNF-like weak inducer of apoptosis (TWEAK) amounts are also greater in all controls except burns. We showed that these proteins acted in synergy to induce the death of keratinocytes in vitro. We also found that TRAIL and TWEAK were secreted by CD1a+ and CD14+ cells present in the blister fluids. Thus, in addition to MHC class I-restricted cytotoxic T lymphocytes (CTLs), which lyse keratinocytes, ligands secreted by non-lymphoid cells capable of inducing keratinocyte death in an MHC class I-independent manner, also seem to be present in the blister fluids of patients with TEN.     

The CD40/CD40 ligand system is expressed in the cutaneous lesions of erythema multiforme and Stevens-Johnson syndrome/toxic epidermal necrolysis spectrum

Background Erythema multiforme (EM) and Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) are determined by a dysregulation of cellular immunity. Objectives To evaluate the effector role of cellular immunity and the involvement of the CD40/CD40 ligand (CD40L) system in the pathogenesis of EM and SJS/TEN. Methods Biopsy specimens from eight patients with EM and six with SJS/TEN were stained for immunohistochemical examination using the alkaline phosphatase/antialkaline phosphatase method. The monoclonal antibodies used included those to CD1a, CD4, CD8, CD40, CD40L, CD68, Fas, Fas ligand (FasL) and myeloperoxidase. Results The cellular infiltrate in both EM and SJS/TEN lesions was composed mainly of T lymphocytes and CD68+ macrophages. We also detected large amounts of neutrophils. Fas and FasL were very highly expressed in SJS and TEN, but weakly in EM. CD40 staining was strong in all tissue sections; there were numerous CD40L+ cells in SJS/TEN but much fewer in EM. Conclusions Activated T lymphocytes and macrophages, but also neutrophils, are presumably the main triggers of mucocutaneous damage in the SJS/TEN disease spectrum. The Fas/FasL system is significantly expressed in SJS/TEN lesions, but not in EM, where this apoptotic pathway presumably does not play a pivotal role in the epidermal damage. We suggest that the CD40/CD40L system may represent an important pathway of induction of SJS/TEN lesions, while in EM it would contribute to the immunoinflammation only as a second‐line mechanism.     

A novel mouse model of atopic dermatitis with epicutaneous allergen sensitization and the effect of Lactobacillus rhamnosus

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease, and the pathogenesis is not completely understood. Although there are some mouse models of AD, it is not easy to establish model to represent the natural AD development in human. In this study, we developed an AD model based on outside–inside theory and investigated the effect of Lactobacillus rhamnosus (Lcr35), which have known as an immune modulator in allergic diseases. SKH‐1 hairless mice underwent three 1‐week exposures (separated by 2‐week intervals) to an ovalbumin (OVA) or saline (control) patch at the same site to develop the mouse model of AD. Lcr35 (1 × 10⁹ CFU) was administered orally every day from 1 week before the first sensitization until the end of the study. The AD model induced erythematous and itchy skin, increasing TEWL and increasing skin inflammation as assessed by histology in the mice. Oral Lcr35 attenuated all disease parameters previously mentioned. OVA‐specific IgE and skin expression of interleukin‐4 (IL‐4) and thymic stromal lymphopoietin (TSLP) increased in AD mice, but were reduced in AD mice treated with Lcr35. Moreover, Lcr35 treatment led to an increase in CD4⁺CD25⁺ Foxp3⁺ Treg cells in the mesenteric lymph nodes of AD mice. In conclusions, based on the ‘outside–inside’ theory, topical allergen may induce AD without skin injury. Oral application of Lcr35 prevented the development of AD in this model by suppressing production of the inflammatory cytokines, IL‐4 and TSLP in the skin via a mechanism that may involve CD4⁺CD25⁺Foxp3⁺Treg cells.