HLA-DR expression on keratinocytes is a common feature of diseased skin

Spatial Mass Cytometry-Based Single-Cell Imaging Reveals a Disrupted Epithelial-Immune Axis in Prurigo Nodularis

Prurigo nodularis (PN) is a chronic, inflammatory skin condition that disproportionately affects African Americans and features intensely pruritic, hyperkeratotic nodules on the extremities and trunk. PN is understudied compared with other inflammatory skin diseases, with the spatial organization of the cutaneous infiltrate in PN yet to be characterized. In this work, we employ spatial imaging mass cytometry to visualize PN lesional skin inflammation and architecture with single-cell resolution through an unbiased machine learning approach. PN lesional skin has increased expression of caspase 3, NF-kB, and phosphorylated signal transducer and activator of transcription 3 compared with healthy skin. Keratinocytes in lesional skin are subdivided into CD14+CD33+, CD11c+, CD63+, and caspase 3-positive innate subpopulations. CD14+ macrophage populations expressing phosphorylated extracellular signal-regulated kinase 1/2 correlate positively with patient-reported itch (P = .006). Hierarchical clustering reveals a cluster of patients with PN with greater atopy, increased NF-kB+ signal transducer and activator of transcription 3-positive phosphorylated extracellular signal-regulated kinase 1/2-positive monocyte-derived myeloid dendritic cells, and increased vimentin expression (P < .05). Neighborhood analysis finds interactions between CD14+ macrophages, CD3+ T cells, monocyte-derived myeloid dendritic cells, and keratinocytes expressing innate immune markers. These findings highlight phosphorylated extracellular signal-regulated kinase-positive CD14+ macrophages as contributors to itch and suggest an epithelial-immune axis in PN pathogenesis.

Human erythroid progenitors express antigen presentation machinery

Early-life immune exposures can profoundly impact lifelong health. However, functional mechanisms underlying fetal immune development remain incomplete. Erythrocytes are not typically considered active immune mediators, primarily because erythroid precursors discard their organelles as they mature, thus losing the ability to alter gene expression in response to stimuli. Erythroid progenitors and precursors circulate in human fetuses and neonates. Although there is limited evidence that erythroid precursors are immunomodulatory, our understanding of the underlying mechanisms remains inadequate. To define the immunobiological role of fetal and perinatal erythroid progenitors and precursors, we analyzed single cell RNA-sequencing data and found that transcriptomics support erythroid progenitors as putative immune mediators. Unexpectedly, we discovered that human erythroid progenitors constitutively express Major Histocompatibility Complex (MHC) class II antigen processing and presentation machinery, which are hallmarks of specialized antigen presenting immune cells. Furthermore, we demonstrate that erythroid progenitors internalize and cleave foreign proteins into peptide antigens. Unlike conventional antigen presenting cells, erythroid progenitors express atypical costimulatory molecules and immunoregulatory cytokines that direct the development of regulatory T cells, which are critical for establishing maternal-fetal tolerance. Expression of MHC II in definitive erythroid progenitors begins during the second trimester, coinciding with the appearance of mature T cells in the fetus, and is absent in primitive progenitors. Lastly, we demonstrate physical and molecular interaction potential of erythroid progenitors and T cells in the fetal liver. Our findings shed light on a unique orchestrator of fetal immunity and provide insight into the mechanisms by which erythroid cells contribute to host defense.

Keratinocytes Present Staphylococcus aureus Enterotoxins and Promote Malignant and Nonmalignant T Cell Proliferation in Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma is characterized by malignant T cells proliferating in a unique tumor microenvironment dominated by keratinocytes (KCs). Skin colonization and infection by Staphylococcus aureus are a common cause of morbidity and are suspected of fueling disease activity. In this study, we show that expression of HLA-DRs, high-affinity receptors for staphylococcal enterotoxins (SEs), by KCs correlates with IFN-γ expression in the tumor microenvironment. Importantly, IFN-γ induces HLA-DR, SE binding, and SE presentation by KCs to malignant T cells from patients with Sézary syndrome and malignant and nonmalignant T-cell lines derived from patients with Sézary syndrome and mycosis fungoides. Likewise, preincubation of KCs with supernatant from patient-derived SE-producing S aureus triggers proliferation in malignant T cells and cytokine release (including IL-2), when cultured with nonmalignant T cells. This is inhibited by pretreatment with engineered bacteriophage S aureus-specific endolysins. Furthermore, alteration in the HLA-DR-binding sites of SE type A and small interfering RNA-mediated knockdown of Jak3 and IL-2Rγ block induction of malignant T-cell proliferation. In conclusion, we show that upon exposure to patient-derived S aureus and SE, KCs stimulate IL-2Rγ/Jak3-dependent proliferation of malignant and nonmalignant T cells in an environment with nonmalignant T cells. These findings suggest that KCs in the tumor microenvironment play a key role in S aureus-mediated disease activity in cutaneous T-cell lymphoma.

Lichen Sclerosus-Incidence and Comorbidity: A Nationwide Swedish Register Study

Background: Data on the incidence and comorbidity of Lichen sclerosus (LS), based on validated nationwide population-based registries, remains scarce. Objective: To explore the incidence and association of comorbidities with LS in Sweden, emphasizing its potential links to malignancies and autoimmune disorders. Methods: A population-based retrospective open cohort study was conducted using the National Patient Register to identify all individuals diagnosed with LS (ICD-10 code L90.0) from 1 January 2001 to 1 January 2021. The study included 154,424 LS patients and a sex and age matched control group of 463,273 individuals to assess the incidence and odds ratios for various cancers and premalignant conditions. Results: The incidence of LS in Sweden was 80.9 per 100,000 person per year, with higher incidence in females (114.4) than in males (47.2). LS patients showed an increased odds ratio for vulvar cancer (OR = 8.3; 95% CI = 7.5-9.0), penile cancer (OR = 8.9; 95% CI = 7.3-11.0), prostate cancer (OR = 1.2; 95% CI = 1.1-1.2), testicular cancer (OR = 1.4; 95% CI = 1.1-1.7), bladder cancer (OR = 1.1; 95% CI = 1.1-1.2), breast cancer (OR = 1.4; 95% CI = 1.3-1.4), leukoplakia of the vulva (OR = 253.5; 95% CI = 221.9-289.6), and leukoplakia of the penis (OR = 5.1; 95% CI = 4.9-5.4). Conclusions: This study underscores the significantly increased association of various cancers and premalignant conditions in LS patients, highlighting the critical need for efficacious treatment and diligent follow-up. The association between LS and autoimmune diseases further necessitates comprehensive investigation to understand the underlying mechanisms and clinical management implications. Future research is essential to confirm these findings and elucidate the role of LS in cancer development.

Comorbidity in patients with Lichen sclerosus: a retrospective cohort study

Lichen sclerosus (LS) is a chronic lymphocyte mediated inflammatory mucocutaneous disease of unknown aetiology with a predilection for the anogenital region, and affecting both sexes. The disease is characterized by pain, intolerable itching and scarring. In late stages of LS, disfiguring scarring can drastically alter the structural anatomical architecture of the genitals. The association between genital LS and different malignant tumours is a concern that needs to be further investigated. An association between LS and several autoimmune diseases has been confirmed in recent studies. All registered citizens of Region Jönköping, Sweden were included in the present study. Patients diagnosed with LS (n = 5680) between 2001 and 2021 were identified using ICD-10 code L90.0 and selected as cases. All other individuals (n = 362 568) served as controls. Odds ratios (ORs) for the selected comorbidity were calculated and adjusted for age and sex. The cumulative incidence of LS for the entire population over a 20-year period was 1.54% (15.4 per 1000 people). The cumulative incidences over a 20-year period for females and males were 2.13% and 0.97%, respectively. This study confirmed the association between LS and vulvar cancer (OR = 17.4; 95% CI 12.1-25.3), penis cancer (OR = 9.1; 95% CI 4.3-18.9), prostate cancer (OR = 2.0; 95% CI 1.6-2.4) and breast cancer (OR = 1.6; 95% CI 1.4-1.8). LS was also associated with Crohn´s disease (OR = 2.0; 95% CI 1.6-2.6) and diabetes mellitus type 1 (OR = 1.9; 95% CI 1.6-2.1). The present study revealed novel important data regarding the association of LS with cancer and autoimmune diseases, emphasising the importance of sufficient treatment and follow-up of patients with LS. However, future studies are needed to confirm these results and the potential role of LS in the development of cancer.

Immunogenic self-peptides - the great unknowns in autoimmunity: Identifying T-cell epitopes driving the autoimmune response in autoimmune diseases

HLA-associated autoimmune diseases likely arise from T-cell-mediated autoimmune responses against certain self-peptides from the broad HLA-presented immunopeptidomes. The limited knowledge of the autoimmune target peptides has so far compromised the basic understanding of autoimmune pathogenesis. This is due to the complexity of antigen processing and presentation as well as the polyspecificity of T-cell receptors (TCRs), which pose high methodological challenges on the discovery of immunogenic self-peptides. HLA-class I molecules present peptides to CD8⁺ T cells primarily derived from cytoplasmic proteins. Therefore, HLA-class I-restricted autoimmune responses should be directed against target cells expressing the corresponding parental protein. In HLA-class II-associated diseases, the origin of immunogenic peptides is not pre-specified, because peptides presented by HLA-class II molecules to CD4⁺ T cells may originate from both extracellular and cellular self-proteins. The different origins of HLA-class I and class II presented peptides determine the respective strategy for the discovery of immunogenic self-peptides in approaches based on the TCRs isolated from clonally expanded pathogenic T cells. Both involve identifying the respective restricting HLA allele as well as determining the recognition motif of the TCR under investigation by peptide library screening, which is required to search for homologous immunogenic self-peptides. In HLA-class I-associated autoimmune diseases, identification of the target cells allows for defining the restricting HLA allotype from the 6 different HLA-class I alleles of the individual HLA haplotype. It furthermore limits the search for immunogenic self-peptides to the transcriptome or immunopeptidome of the target cells, although neoepitopes generated by peptide splicing or translational errors may complicate identification. In HLA class II-associated autoimmune diseases, the lack of a defined target cell and differential antigen processing in different antigen-presenting cells complicate identification of the HLA restriction of autoreactive TCRs from CD4⁺ T cells. To avoid that all corresponding HLA-class II allotypes have to be included in the peptide discovery, autoantigens defined by autoantibodies can guide the search for immunogenic self-peptides presented by the respective HLA-class II risk allele. The objective of this article is to highlight important aspects to be considered in the discovery of immunogenic self-peptides in autoimmune diseases.

Reduced cutaneous CD200:CD200R1 signaling in psoriasis enhances neutrophil recruitment to skin

INTRODUCTION

The skin immune system is tightly regulated to prevent inappropriate inflammation in response to harmless environmental substances. This regulation is actively maintained by mechanisms including cytokines and cell surface receptors and its loss results in inflammatory disease. In the case of psoriasis, inappropriate immune activation leads to IL-17-driven chronic inflammation, but molecular mechanisms underlying this loss of regulation are not well understood. Immunoglobulin family member CD200 and its receptor, CD200R1, are important regulators of inflammation. Therefore, we determined if this pathway is dysregulated in psoriasis, and how this affects immune cell activity.

METHODS

Human skin biopsies were examined by quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. The role of CD200R1 in regulating psoriasis-like skin inflammation was examined using CD200R1 blocking antibodies in mouse psoriasis models. CD200R1 blocking antibodies were also used in an in vivo neutrophil recruitment assay and in vitro assays to examine macrophage, innate lymphoid cell, γδ T cell, and neutrophil activity.

RESULTS

We reveal that CD200 and signaling via CD200R1 are reduced in non-lesional psoriasis skin. In mouse models of psoriasis CD200R1 was shown to limit psoriasis-like inflammation by enhancing acanthosis, CCL20 production and neutrophil recruitment, but surprisingly, macrophage function and IL-17 production were not affected, and neutrophil reactive oxygen species production was reduced.

CONCLUSION

Collectively, these data show that CD200R1 affects neutrophil function and limits inflammatory responses in healthy skin by restricting neutrophil recruitment. However, the CD200 pathway is reduced in psoriasis, resulting in a loss of immune control, and increased neutrophil recruitment in mouse models. In conclusion, we highlight CD200R1:CD200 as a pathway that might be targeted to dampen inflammation in patients with psoriasis.

Antigen Processing, Presentation, and Tolerance: Role in Autoimmune Skin Diseases

Autoreactive T cells pose a constant risk for the emergence of autoimmune skin diseases in genetically predisposed individuals carrying certain HLA risk alleles. Immune tolerance mechanisms are opposed by broad HLA-presented self-immunopeptidomes, a predefined repertoire of polyspecific TCRs, the continuous generation of new antibody specificities by somatic recombination of Ig genes in B cells, and heightened proinflammatory reactivity. Increased autoantigen presentation by HLA molecules, cross-activation of pathogen-induced T cells against autologous structures, altered metabolism of self-proteins, and excessive production of proinflammatory signals may all contribute to the breakdown of immune tolerance and the development of autoimmune skin diseases.

Infection-provoked psoriasis: Induced or aggravated (Review)

Psoriasis is a common chronic, immune-mediated, inflammatory skin disorder, with a reported prevalence of 0.0-2.1% among children and 0.91-8.50% among adults, worldwide. Psoriasis is induced by several environmental factors, including infection, alcohol consumption, drugs, trauma, acute withdrawal of systemic or potent topical corticosteroids, body mass index and endocrine disorders. Increasing evidence suggest that a variety of microorganisms play key roles in the induction and exacerbation of psoriasis. Pathogens, such as streptococci and staphylococci are considered causal factors, presumably via superantigen activation of skin-seeking T cells. In addition, fungal pathogens, such as Candida and Malassezia, and viral agents, such as human immunodeficiency virus, hepatitis C virus infection and human papillomavirus, are also closely associated with psoriasis. Recently, several types of pathogens, such as Helicobacter pylori infection, Zika virus and scabies, have been reported to potentially trigger psoriasis. The present review discusses the underlying molecular mechanisms by which these infections influence psoriasis to provide a better understanding of the pathogenesis of psoriasis.

Nod-Like Receptors in Host Defence and Disease at the Epidermal Barrier

The nucleotide-binding domain and leucine-rich-repeat-containing family (NLRs) (sometimes called the NOD-like receptors, though the family contains few bona fide receptors) are a superfamily of multidomain-containing proteins that detect cellular stress and microbial infection. They constitute a critical arm of the innate immune response, though their functions are not restricted to pathogen recognition and members engage in controlling inflammasome activation, antigen-presentation, transcriptional regulation, cell death and also embryogenesis. NLRs are found from basal metazoans to plants, to zebrafish, mice and humans though functions of individual members can vary from species to species. NLRs also display highly wide-ranging tissue expression. Here, we discuss the importance of NLRs to the immune response at the epidermal barrier and summarise the known role of individual family members in the pathogenesis of skin disease.

The Immune Functions of Keratinocytes in Skin Wound Healing

As the most dominant cell type in the skin, keratinocytes play critical roles in wound repair not only as structural cells but also exerting important immune functions. This review focuses on the communications between keratinocytes and immune cells in wound healing, which are mediated by various cytokines, chemokines, and extracellular vesicles. Keratinocytes can also directly interact with T cells via antigen presentation. Moreover, keratinocytes produce antimicrobial peptides that can directly kill the invading pathogens and contribute to wound repair in many aspects. We also reviewed the epigenetic mechanisms known to regulate keratinocyte immune functions, including histone modifications, non-protein-coding RNAs (e.g., microRNAs, and long noncoding RNAs), and chromatin dynamics. Lastly, we summarized the current evidence on the dysregulated immune functions of keratinocytes in chronic nonhealing wounds. Based on their crucial immune functions in skin wound healing, we propose that keratinocytes significantly contribute to the pathogenesis of chronic wound inflammation. We hope this review will trigger an interest in investigating the immune roles of keratinocytes in chronic wound pathology, which may open up new avenues for developing innovative wound treatments.

Therapeutic applications of the selective high affinity ligand drug SH7139 extend beyond non-Hodgkin's lymphoma to many other types of solid cancers

SH7139, the first of a series of selective high affinity ligand (SHAL) oncology drug candidates designed to target and bind to the HLA-DR proteins overexpressed by B-cell lymphomas, has demonstrated exceptional efficacy in the treatment of Burkitt lymphoma xenografts in mice and a safety profile that may prove to be unprecedented for an oncology drug. The aim of this study was to determine how frequently the HLA-DRs targeted by SH7139 are expressed by different subtypes of non-Hodgkin’s lymphoma and by other solid cancers that have been reported to express HLA-DR. Binding studies conducted with SH7129, a biotinylated analog of SH7139, reveal that more than half of the biopsy sections obtained from patients with different types of non-Hodgkin’s lymphoma express the HLA-DRs targeted by SH7139. Similar analyses of tumor biopsy tissue obtained from patients diagnosed with eighteen other solid cancers show the majority of these tumors also express the HLA-DRs targeted by SH7139. Cervical, ovarian, colorectal and prostate cancers expressed the most HLA-DR. Only a few esophageal and head and neck tumors bound the diagnostic. Within an individual’s tumor, cell to cell differences in HLA-DR target expression varied by only 2 to 3-fold while the expression levels in tumors obtained from different patients varied as much as 10 to 100-fold. The high frequency with which SH7129 was observed to bind to these cancers suggests that many patients diagnosed with B-cell lymphomas, myelomas, and other non-hematological cancers should be considered potential candidates for new therapies such as SH7139 that target HLA-DR-expressing tumors.

Psoriasis in HIV infection: an update

Psoriasis is a prevalent systemic immune-mediated disease with cutaneous manifestations. In HIV-infected patients, psoriasis may have a higher incidence, present atypical and more exuberant clinical features, and is frequently recalcitrant to treatment. Despite this aggravated severity, treatment options for psoriasis in HIV-infected individuals remain limited due to the risk of fatal immunosuppression associated with both classical immunosuppressants and new biological drugs. Notwithstanding, drug therapy in psoriasis has been undergoing major advances for the last few years, with novel drugs approved, which could significantly add to the management of HIV-infected patients. It is therefore our aim to present a review of the available literature to highlight the updated evidence on psoriasis in HIV-infected individuals, particularly in regards to its epidemiology, proposed pathophysiology, clinical presentation, currently available therapeutic options, and future perspectives.

Epidermal Overexpression of Xenobiotic Receptor PXR Impairs the Epidermal Barrier and Triggers Th2 Immune Response

The skin is in daily contact with environmental pollutants, but the long-term effects of such exposure remain underinvestigated. Many of these toxins bind and activate the pregnane X receptor (PXR), a ligand-activated transcription factor that regulates genes central to xenobiotic metabolism. The objective of this work was to investigate the effect of constitutive activation of PXR in the basal layer of the skin to mimic repeated skin exposure to noxious molecules. We designed a transgenic mouse model that overexpresses the human PXR gene linked to the herpes simplex VP16 domain under the control of the keratin 14 promoter. We show that transgenic mice display increased transepidermal water loss and elevated skin pH, abnormal stratum corneum lipids, focal epidermal hyperplasia, activated keratinocytes expressing more thymic stromal lymphopoietin, a T helper type 2/T helper type 17 skin immune response, and increased serum IgE. Furthermore, the cutaneous barrier dysfunction precedes development of the T helper type 2/T helper type 17 inflammation in transgenic mice, thereby mirroring the time course of atopic dermatitis development in humans. Moreover, further experiments suggest increased PXR signaling in the skin of patients with atopic dermatitis when compared with healthy skin. Thus, PXR activation by environmental pollutants may compromise epidermal barrier function and favor an immune response resembling atopic dermatitis.

Gamma-interferon-inducible lysosomal thiol reductase is upregulated in human melanoma

T-cell-mediated immunity has the ability to produce durable antimelanoma responses, resulting in improved survival of patients with advanced melanoma. Antigen presentation is a key determinant of T-cell responses. Gamma-interferon-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of multiple melanoma antigens to CD4+ T cells. However, GILT expression in melanoma has not been defined. We evaluated GILT and MHC class II expression in human primary and metastatic melanomas and nevi using immunohistochemical analysis. GILT staining in melanocytes was observed in 70% of primary and 58% of metastatic melanomas versus 0% of nevi. When present, the GILT staining intensity in melanocytes was typically faint. Both GILT and MHC class II expression were increased in melanocytes of primary and metastatic melanomas compared with nevi. GILT staining in antigen-presenting cells (APCs) was detected in 100% of primary and metastatic melanomas versus 31% of nevi, and it was typically intense. GILT expression was increased in APCs of primary and metastatic melanomas compared with nevi, whereas MHC class II had equivalent high expression in APCs of all melanocytic lesions. GILT staining in keratinocytes was detected in 67% of primary melanomas versus 14% of nevi and 6% of metastatic melanomas. GILT, but not MHC class II, expression was increased in keratinocytes of primary melanomas compared with nevi and metastases. GILT expression is anticipated to result in improved presentation of melanoma antigens and more effective antimelanoma T-cell responses. GILT expression may be a biomarker of immune recognition of melanoma.

Major histocompatibility complex class I and class II alleles may confer susceptibility to or protection against morphea: findings from the Morphea in Adults and Children cohort

OBJECTIVE

To determine the HLA class I and class II alleles of the human major histocompatibility complex showing an association with morphea (localized scleroderma) in the Morphea in Adults and Children (MAC) cohort, using a nested case-control association study.

METHODS

Patients with morphea were identified from the MAC cohort, and matched controls were obtained from the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases Scleroderma Family Registry and DNA Repository and from the Division of Rheumatology at the University of Texas Health Science Center at Houston. HLA class II genotyping and single-strand conformational polymorphism typing were performed to identify HLA-A, B, and C alleles. Associations between HLA class I and class II alleles and morphea, as well as its subphenotypes, were determined.

RESULTS

Two hundred eleven patients with morphea and 726 matched controls were available for HLA class I typing, and 158 patients with morphea and 1,008 matched controls were available for HLA class II typing. The strongest associations were found with DRB1*04:04 (odds ratio [OR] 2.3, 95% confidence interval [95% CI] 1.4-4.0, P = 0.002), and HLA-B*37 conferred the highest OR among the class I alleles (OR 3.2, 95% CI 1.5-6.5, P = 0.001). Comparison of the risk allele profile in this cohort with the risk alleles previously identified in patients with systemic sclerosis, determined using the same methods and same control population, revealed one allele in common, DRB*04:04.

CONCLUSION

These results demonstrate that specific HLA class I and class II alleles are associated with morphea and are also likely to be associated with generalized and linear subtypes of morphea. The morphea-associated alleles are different from those found in scleroderma, suggesting that morphea is immunogenetically distinct. Risk alleles in morphea are also associated with conditions such as rheumatoid arthritis (RA) and other autoimmune conditions. Population-based studies have indicated that patients with RA have an increased risk of morphea, and therefore a common susceptibility allele may be implicated.

Immunohistochemical characterization of non-epithelial cells in spiradenoma

Spiradenoma is unique with respect to the presence of a large number of non-epithelial cells, including S100 protein(+) cells, most of which are presumably Langerhans cells, in the parenchyma as shown in the published work. However, the characterization of these non-epithelial cells to date is insufficient. Immunohistochemistry of CD1a, CD3, CD4, CD8, CD56, CD68, intercellular adhesion molecule-1 (ICAM-1), and HLA-DR, as well as double-immunofluorescence labeling of S100 protein/CD1a and CD1a/CD3, was performed using paraffin-embedded specimens from five cases of spiradenoma retrospectively. Non-epithelial cells evenly distributed throughout the parenchyma of spiradenoma primarily consisted of CD1a(+) Langerhans cells and CD3(+) T cells. ICAM-1 was expressed by epithelial cells and non-epithelial cells in the parenchyma. HLA-DR on the epithelial cells was limited to the focal area. In double-immunofluorescence labeling, approximately one-half of Langerhans cells were spatially related to T cells in the parenchyma, suggesting their functional interaction.

Engineering a skin replacement

Major skin loss from trauma or burns cannot always be replaced with the patient's own skin. An engineered skin replacement would restore the barrier function of the skin, remain permanently on the wound, and minimize late functional complications of wound contraction. Cultured epithelial autograft (CEA) sheets reproduce the epidermis' function and have been used in burn patients to close large wounds. There are several promising avenues for dermal replacement, but none has yet had wide clinical application.

StrataGraft skin substitute is well-tolerated and is not acutely immunogenic in patients with traumatic wounds: results from a prospective, randomized, controlled dose escalation trial

OBJECTIVE

The goal of this study was to assess the immunogenicity and antigenicity of StrataGraft skin tissue in a randomized phase I/II clinical trial for the temporary management of full-thickness skin loss.

BACKGROUND

StrataGraft skin tissue consists of a dermal equivalent containing human dermal fibroblasts and a fully stratified, biologically active epidermis derived from Near-diploid Immortalized Keratinocyte S (NIKS) cells, a pathogen-free, long-lived, consistent, human keratinocyte progenitor.

METHODS

Traumatic skin wounds often require temporary allograft coverage to stabilize the wound bed until autografting is possible. StrataGraft and cadaveric allograft were placed side by side on 15 patients with full-thickness skin defects for 1 week before autografting. Allografts were removed from the wound bed and examined for allogeneic immune responses. Immunohistochemistry and indirect immunofluorescence were used to assess tissue structure and cellular composition of allografts. In vitro lymphocyte proliferation assays, chromium-release assays, and development of antibodies were used to examine allogeneic responses.

RESULTS

One week after patient exposure to allografts, there were no differences in the numbers of T or B lymphocytes or Langerhans cells present in StrataGraft skin substitute compared to cadaver allograft, the standard of care. Importantly, exposure to StrataGraft skin substitute did not induce the proliferation of patient peripheral blood mononuclear cells to NIKS keratinocytes or enhance cell-mediated lysis of NIKS keratinocytes in vitro. Similarly, no evidence of antibody generation targeted to the NIKS keratinocytes was seen.

CONCLUSIONS

These findings indicate that StrataGraft tissue is well-tolerated and not acutely immunogenic in patients with traumatic skin wounds. Notably, exposure to StrataGraft did not increase patient sensitivity toward or elicit immune responses against the NIKS keratinocytes. We envision that this novel skin tissue technology will be widely used to facilitate the healing of traumatic cutaneous wounds.This study was registered at www.clinicaltrials.gov (NCT00618839).

Antigen presentation and MHC class II expression by human esophageal epithelial cells: role in eosinophilic esophagitis

Professional antigen-presenting cells (APCs) play a crucial role in initiating immune responses. Under pathological conditions, epithelial cells at mucosal surfaces act as nonprofessional APCs, thereby regulating immune responses at the site of exposure. Epithelial cells in the esophagus may contribute to the pathogenesis of eosinophilic esophagitis (EoE) by presenting antigens on the major histocompatibility complex (MHC) class II. Our goal was to demonstrate the ability of esophageal epithelial cells to process and present antigens on the MHC class II system and to investigate the contribution of epithelial cell antigen presentation to EoE. Immunohistochemistry detected HLA-DR, CD80, and CD86 expression and enzyme-linked immunosorbent assay detected interferon-γ (IFNγ) in esophageal biopsies. Antigen presentation was studied using the human esophageal epithelial cell line HET-1A by reverse transcriptase-PCR, flow cytometry, and confocal microscopy. T helper cell lymphocyte proliferation was assessed by flow cytometry and IL-2 secretion. IFNγ and MHC class II were increased in mucosa of patients with EoE. IFNγ increased mRNA of HLA-DP, HLA-DQ, HLA-DR, and CIITA in HET-1A cells. HET-1A engulfed cell debris and processed ovalbumin. HET-1A cells expressed HLA-DR after IFNγ treatment. HET-1A stimulated T helper cell activation. In this study, we demonstrated the ability of esophageal epithelial cells to act as nonprofessional APCs in the presence of IFNγ. Esophageal epithelial cell antigen presentation may contribute to the pathophysiology of eosinophilic esophagitis.

MHC class II expression by follicular keratinocytes in canine demodicosis—An immunohistochemical study

MHC class II proteins present fragments of extra cellular antigen to stimulate CD4(+) T lymphocytes. Aim of this study was the detection of MHC class II antigens on different cutaneous cells in canine demodicosis. Histopathological and immunohistochemical examination of skin biopsies from 44 dogs with demodicosis is reported. The control group consisted of skin biopsies taken from 10 necropsied dogs without obvious skin lesions. The immunohistological assessment of the MHC class II expression revealed MHC class II proteins on different cell types of infiltrating inflammatory cells, i.e. APCs (antigen-presenting cells), macrophages, T lymphocytes and B lymphocytes. The plasma cells, however, only showed expression in 32 (73%) of 44 cases. Generally it was noticeable that most plasma cells but never all of them expressed MHC class II. Neutrophils, mast cells and eosinophils were MHC class II negative. Furthermore, in 39 biopsies (89%) from dogs with demodicosis MHC class II positive follicular keratinocytes were found. The control group did not show MHC class II expression on epithelial cells. Concerning the endothelial cells, a total of 25 biopsies (57%) showed MHC class II expression in which different vascular plexuses were affected by staining. This examination shows that MHC class II expression in the skin of dogs suffering form demodicosis is elevated. Especially the MHC class II expression by follicular keratinocytes seems to be conspicuous. We hypothesize that this is in association with the development and the maintenance of follicular inflammation.

Cytokine alterations in lichen sclerosus: an immunohistochemical study

BACKGROUND

Although the histology of lichen sclerosus is characteristic, the precise nature of the inflammatory changes and the signals provoking them is uncertain.

OBJECTIVES

To delineate the inflammatory changes in lichen sclerosus more accurately by studying cytokine changes.

METHODS

An immunohistochemical study of 12 specimens of genital lichen sclerosus and one specimen of extragenital lichen sclerosus was undertaken using monoclonal antibodies to interferon (IFN)-gamma, IFN-gamma receptor, tumour necrosis factor (TNF)-alpha, interleukin (IL)-1alpha, IL-2 receptor (CD25), intercellular adhesion molecule-1 (ICAM-1) and its ligand CD11a. Control specimens were seven specimens of normal vulva obtained during gynaecological procedures, three specimens of normal skin, adjacent uninvolved thigh from three of the patients with lichen sclerosus, five specimens of nonvulval psoriasis, four specimens of nonvulval lichen planus and two specimens from chronic wounds.

RESULTS

The lichen sclerosus specimens demonstrated slightly increased staining for IFN-gamma within the epidermis compared with the normal vulva and nonvulval skin. There was increased dermal staining for IFN-gamma both within the pale zone of the upper dermis and within the inflammatory zone below this. We confirmed our previous demonstration that in lichen sclerosus HLA-DR immunostaining is increased in association with vascular endothelium, the inflammatory cell infiltrate and around the keratinocytes. The areas of the epidermis with the strongest immunostaining for HLA-DR generally also had the strongest staining for IFN-gamma. In the lichen sclerosus specimens the zone of inflammation also demonstrated increased immunostaining for TNF-alpha, IL-1alpha, IFN-gamma receptor, CD25, CD11a and ICAM-1 while the zone of sclerosus demonstrated a smaller increase in immunostaining for IFN-gamma receptor, TNF-alpha, CD11a and ICAM-1, and the epidermis demonstrated increased staining for ICAM-1.

CONCLUSIONS

The increased staining for IFN-gamma, TNF-alpha, IL-1alpha, IFN-gamma receptor, CD25, CD11a and ICAM-1 suggest that the cytokine response in lichen sclerosus shares characteristics of the cytokine response in lichen planus and chronic wounds.

Pityriasis lichenoides and its subtypes

Pityriasis lichenoides represents a unique group of inflammatory skin disorders that include pityriasis lichenoides et varioliformis acuta (PLEVA), febrile ulceronecrotic Mucha-Habermann disease (a subtype of PLEVA), and pityriasis lichenoides chronica. The history, epidemiology, clinical features, pathophysiology, and treatment of this group of conditions are reviewed in this manuscript.

Microbeads and anchorage-dependent eukaryotic cells: the beginning of a new era in biotechnology

Modern methods for the mass cultivation of anchorage-dependent mammalian cells started with the advent of microcarrier technology. Largely for reasons pertaining to their mode of preparation and ease of cultivation, 150-230 microns microbeads have been overwhelmingly adopted and the technology around them developed. To meet high biomass, macroporous microbeads have been developed. Also, the chemistry of the microsupport has been adapted in order to afford better protection of fragile cells to mechanical wear while simultaneously reorienting their differentiation towards the sought aims (production of cytokines, enzymes etc. ...). Future progress depends upon solutions being brought to problems inherent to this new technology (maintenance of steady state conditions of growth etc. ...) as well as to requirements arising from animal cell culture in general (biosensors, bioreactor's design etc. ...). Besides such technical implementations, biology at large is also expected to benefit from the advent of microcarriers in fields as diverse as the preparation of metaphasic chromosomes in bulk, toxicity testing, organ reconstitution following cell transplantation etc.

Prolonged MHC class II expression and CIITA transcription in human keratinocytes

A transcriptional cofactor, the MHC class II transactivator (CIITA), is a master regulator of MHC class II gene expression. CIITA expression is restricted in MHC class II-positive cells and is regulated by 4 (human) or 3 (mouse) promoters. To clarify the usage of human CIITA promoters in keratinocytes, we analyzed CIITA mRNA levels in IFN-gamma-stimulated normal human keratinocytes (NHK) by real-time PCR using promoter-specific primers. When the amount of total CIITA mRNA in NHK was quantified at 6h after IFN-gamma-stimulation, the amount of CIITA mRNA detected in NHK did not differ from that seen in the B cell line Raji or the IFN-gamma-stimulated macrophage cell line THP-1. Quantitative real-time PCR using promoter-specific primers showed that type IV CIITA mRNA was strongly transcribed and that type III CIITA mRNA was weakly transcribed in stimulated NHK, while no transcripts from pI and pII were detected. Although type IV mRNA in THP-1 was transiently transcribed by IFN-gamma-stimulation, transcription of type IV in IFN-gamma-stimulated keratinocytes was prolonged. This difference subsequently caused significantly higher expression at 72 h of MHC class II on NHK, compared with THP-1. This is the first report to quantitatively analyze each type of CIITA transcript in NHK.

Life-threatening graft-vs-host disease

Hematopoietic stem cell transplant (SCT) is considered standard therapy for a variety of malignant and nonmalignant diseases. Graft-versus-host disease (GVHD) still represents today a major complication of hematopoietic SCT. Two types of GVHD have traditionally been recognized on the basis of the time of onset following transplantation, distinct pathobiological pathways, and different clinical presentations. The acute form commonly breaks out 2 to 6 weeks after transplantation, affecting up to 60% of patients receiving allogeneic transplants from HLA identical donors. Transfer of immunocompetent donor T cells contained in the graft may undergo alloreactivity against recipient cells because of major or minor histocompatibility antigens disparities between the donor and the immunosuppressed host. Target specificity in acute GVHD involves preferential injury to epithelial surfaces of the skin and mucous membranes, biliary ducts of the liver, and crypts of the intestinal tract. Chronic GVHD affects approximately 30% to 80% of patients surviving 6 months or longer after stem cell transplantation and is the leading cause of nonrelapse deaths occurring more than 2 years after transplantation. Chronic GVHD is a multiorgan syndrome with clinical features suggesting some autoimmune diseases, and possibly both alloreactive and autoreactive T cell clones are involved in its pathophysiology. Although GVHD may convey beneficial graft-versus-leukemia/lymphoma effects, it also entails a significant risk of morbidity and mortality. Patients with mild GVHD need only minimal, if any, immunosuppressive treatment, whereas prognosis of patients with extensive disease or resistant to standard immunosuppressive treatment may be dismal. Early recognition of GVHD followed by prompt therapeutic intervention may prevent the progression to higher-grade disease and improve the outcome for patients receiving hematopoietic SCT.

Expression of C‐type lectin receptors by subsets of dendritic cells in human skin

C-type lectins are cell surface receptors that recognize carbohydrate structures which are often part of microbial pathogens. Several of these molecules are expressed on dendritic cells and are involved in antigen uptake. Expression of C-type lectins on dendritic cells of the human skin, i.e. Langerhans cells of the epidermis and dermal dendritic cells, has been incompletely studied to date. We therefore investigated C-type lectins in situ and on dendritic cells obtained by migration from skin explants by immunofluorescence and flow cytometry. Emphasis was laid on expression patterns of DEC-205/CD205 and BDCA-2, a marker for plasmacytoid dendritic cells. Langerhans cells in situ expressed low levels of DEC-205. Expression was upregulated upon maturation in skin explant organ culture. Most dermal dendritic cells were found to be positive for DEC-205 and DC-SIGN/CD209. Few BDCA-2-expressing cells were found in most skin samples. They were located in small groups in the dermis close beneath the basement membrane. The vast majority of all types of dendritic cells in normal human skin was of immature phenotype, i.e. did not express DC-LAMP/CD208. It is concluded that normal appearing human skin harbors different subsets of dendritic cells including few scattered BDCA-2-expressing cells, presumably plasmacytoid dendritic cells, expressing variable sets of C-type lectin receptors. This may critically contribute to the capacity of the skin immune system to flexibly respond to the world of microbial pathogens.

The E5 protein of human papillomavirus type 16 perturbs MHC class II antigen maturation in human foreskin keratinocytes treated with interferon-gamma

Major histocompatibility complex (MHC) class II antigens are expressed on human foreskin keratinocytes (HFKs) following exposure to interferon gamma. The expression of MHC class II proteins on the cell surface may allow keratinocytes to function as antigen-presenting cells and induce a subsequent immune response to virus infection. Invariant chain (Ii) is a chaperone protein which plays an important role in the maturation of MHC class II molecules. The sequential degradation of Ii within acidic endocytic compartments is a key process required for the successful loading of antigenic peptide onto MHC class II molecules. Since human papillomavirus (HPV) 16 E5 can inhibit the acidification of late endosomes in HFKs, the E5 protein may be able to affect proper peptide loading onto the MHC class II molecule. To test this hypothesis, HFKs were infected with either control virus or a recombinant virus expressing HPV16 E5 and the infected cells were subsequently treated with interferon-gamma. ELISAs revealed a decrease of MHC class II expression on the surface of E5-expressing cells compared with control virus-infected cells after interferon treatment. Western blot analysis showed that, in cells treated with interferon gamma, E5 could prevent the breakdown of Ii and block the formation of peptide-loaded, SDS-stable mature MHC class II dimers, correlating with diminished surface MHC class II expression. These data suggest that HPV16 E5 may be able to decrease immune recognition of infected keratinocytes via disruption of MHC class II protein function.

Immune-mediated loss of transgene expression in skin: implications for cutaneous gene therapy

A clearer understanding of the immune-mediated loss of transgene from cutaneous epithelium is necessary for development of effective clinical gene therapy protocols for patients who carry null mutations in the target gene. We have used retrovirus-mediated transfer of lacZ to mouse skin as a model to investigate the mechanism of immune-mediated transgene loss in skin. Transduction of C57Bl/6 mouse skin resulted in elicitation of both humoral and cellular immune responses. Antibody responses did not play a major role in the loss of transgene. Infiltration of the transduced skin with CD4(+) and CD8(+) cells and induction of transgene-specific cytotoxic T lymphocytes implied a role for T-cell-mediated responses. Transduction of mice deficient in either major histocompatibility complex (MHC) class I or class II molecules resulted in transient transgene expression. Only in MHC(-/-) mice lacking expression of both class I and class II MHC molecules was persistent transgene expression seen. These data indicate a primary role for T-cell-mediated responses in the immune-mediated loss of transgene expression. Furthermore, CD4 and CD8 T cells have overlapping roles and either population can effectively eliminate transduced cells. Therefore, long-term cutaneous gene therapy may require development of strategies to interfere with activation or function of both T cell populations.

Possible mechanisms of hypopigmentation in lichen sclerosus

Lichen sclerosus (LS) shares with vitiligo a milky-white appearance. By biopsy, pathognomonic dermal sclerosis readily distinguishes LS from vitiligo and other causes of leukoderma. To determine what the mechanism of hypopigmentation is in LS, we examined samples from LS cases for alterations in melanin content (Fontana-Masson stain) and melanocyte number (HMB-45 [PMEL-17/gp100], Mel-5 [TRP-1], Mart-1 [Melan A]) and compared these findings with those in controls of normal skin, acute scars, vitiligo, and lichen planus (LP; a common inflammatory cause of hyperpigmentation). The degree and extent of melanization found in LS overlapped with that in acute scars showing predominantly hypomelanized keratinocytes, with that in LP containing regions with numerous melanophages, and with that in vitiligo exhibiting focal regions of keratinocytes devoid of melanin pigment. By hematoxylin-eosin staining and immunocytochemistry for Mel-5 and Mart-1, LS had a lower mean count of melanocytes than acute scars, LP, and normal skin per 200 basal keratinocytes. In addition, a few LS cases had a significant loss of melanocytes comparable to that of vitiligo. Surprisingly, Mart-1 identified rare melanocytes in 67% of vitiligo cases and a significantly larger pool of melanocytes in LS and controls other than those labeled by Mel-5. Furthermore, LP and evolving lesions of LS contained the highest Mart-1 counts. HMB-45-immunoreactive melanocytes were found in the majority of acute scars and in LP and late-stage LS lesions at significantly lower levels than Mel-5- and Mart-1- labeled melanocytes, but they were not found in vitiligo or normal skin. We propose that several mechanisms may play a role in the production of leucoderma in LS: 1) decreased melanin production; 2) block in transfer of melanosomes to keratinocytes; and 3) melanocyte loss. The latter finding may be the pathogenic connection (lichenoid dermatitis of LS triggering an autoimmune reaction to melanocytes) that underlies the documented association of LS with vitiligo.

Calprotectin expression by gingival epithelial cells

Calprotectin, a heterodimer of MRP8 and MRP14 with antimicrobial properties, is found in the cytosol of neutrophils, monocytes, and human gingival keratinocytes. During inflammation of the oral mucosa, the expression of immunoreactive calprotectin appears upregulated. Given the possible cell sources, we sought to learn if epithelial cells upregulate calprotectin in response to proinflammmatory agents. First, human gingival keratinocytes were maintained in primary culture until senescence. At each passage, cells were harvested and analyzed for quantitative expression of MRP8 and MRP14 subunit mRNA by RNase protection assays and calprotectin complex by enzyme-linked immunosorbent assay. Calprotectin expression was constitutive in the primary gingival keratinocytes, but calprotectin-specific mRNA and protein tended to increase as the cells neared senescence. To test whether calprotectin expression was inducible, immortalized gingival keratinocyte cultures were treated for 2 to 4 h with lipopolysaccharide (LPS) or interleukin-1 beta (IL-1 beta). As a positive control for inducible expression, immortalized keratinocytes were incubated with phorbol myristate acetate (PMA) (50 ng/ml) for 24 h. Incubation with PMA stimulated increased expression of MRP8 and MRP14 mRNA within 2 h, peaking within 5 h. MRP8- and MRP14-specific mRNA expression by immortalized keratinocytes appeared to be unaffected by LPS or IL-1 beta. In contrast, LPS, IL-1 beta, and PMA each upregulated IL-8. These data show that calprotectin mRNA is expressed constitutively in cultured keratinocytes, while expression by immortalized cells appears to be independent of the exogenous proinflammatory agents LPS and IL-1 beta.

Blockade of T lymphocyte costimulation with cytotoxic T lymphocyte-associated antigen 4-immunoglobulin (CTLA4Ig) reverses the cellular pathology of psoriatic plaques, including the activation of keratinocytes, dendritic cells, and endothelial cells

Efficient T cell activation is dependent on the intimate contact between antigen-presenting cells (APCs) and T cells. The engagement of the B7 family of molecules on APCs with CD28 and CD152 (cytotoxic T lymphocyte-associated antigen 4 [CTLA-4]) receptors on T cells delivers costimulatory signal(s) important in T cell activation. We investigated the dependence of pathologic cellular activation in psoriatic plaques on B7-mediated T cell costimulation. Patients with psoriasis vulgaris received four intravenous infusions of the soluble chimeric protein CTLA4Ig (BMS-188667) in a 26-wk, phase I, open label dose escalation study. Clinical improvement was associated with reduced cellular activation of lesional T cells, keratinocytes, dendritic cells (DCs), and vascular endothelium. Expression of CD40, CD54, and major histocompatibility complex (MHC) class II HLA-DR antigens by lesional keratinocytes was markedly reduced in serial biopsy specimens. Concurrent reductions in B7-1 (CD80), B7-2 (CD86), CD40, MHC class II, CD83, DC-lysosomal-associated membrane glycoprotein (DC-LAMP), and CD11c expression were detected on lesional DCs, which also decreased in number within lesional biopsies. Skin explant experiments suggested that these alterations in activated or mature DCs were not the result of direct toxicity of CTLA4Ig for DCs. Decreased lesional vascular ectasia and tortuosity were also observed and were accompanied by reduced presence of E-selectin, P-selectin, and CD54 on vascular endothelium. This study highlights the critical and proximal role of T cell activation through the B7-CD28/CD152 costimulatory pathway in maintaining the pathology of psoriasis, including the newly recognized accumulation of mature DCs in the epidermis.

Comparative immunophenotypic study of lichen sclerosus: epidermotropic CD57+ lymphocytes are numerous--implications for pathogenesis

To characterize the immunophenotype of inflammatory cells in lichen sclerosus (LS), we performed a comparative case control study using one- and two-color immunohistochemistry and the nitro blue tetrazolium (NBT) reaction. Study material consisted of 100 biopsies from patients with LS or from 12 control groups consisting of inflammatory, scarring, and depigmenting cutaneous disorders. In addition, fresh tissue was sampled from four vulvectomy specimens for NBT testing. The typical inflammatory infiltrate of LS contained numerous epidermotropic CD3+, CD8+, CD57+ cells, increased intraepidermal HLA-DR+ cells, and a dermal infiltrate rich in CD8+, CD57+, HLA-DR+, and CD68+ inflammatory cells. Comparing LS to the 12 control groups, epidermotropic CD57+ lymphocytes independently predicted LS (P = 0.006, logistic regression, multivariate analysis). Among the 12 control groups, only specimens of the inflammatory stage of morphea exhibited numerous dermal CD57+ lymphocytes. Two-color immunohistochemistry confirmed the CD3+/CD8+CD57+ and CD3+/ CD8+/CD57+HLA-DR+ epidermotropic and dermal lymphocytic phenotypes and the dermal macrophage CD68+HLA-DR+ phenotype. In LS, the NBT reaction revealed evidence of superoxide production associated with CD68+HLA-DR+ cells. Expansion of CD8+CD57+lymphocytes is associated with viral infections, autoimmune disease, malignancies, and transplantation and is suspected to be the result of chronic excessive antigen challenge. In these pathologic states, CD8+CD57+ lymphocytes (as terminally differentiated, antigen-specific T cells) participate in the suppression of cytolytic activity to limit tissue damage. In LS, activated macrophages and lymphocytes indicate persistent antigen-driven inflammation. LS's numerous CD8+CD57+ lymphocytes may be either the mediators or the consequence of its hallmark sclerosis.

Interleukins 18 and 12 synergistically upregulate interferon-gamma production by murine dendritic epidermal T cells

A unique subset of gammadelta T cells, termed dendritic epidermal T cells, reside in murine epidermis. It was previously reported that freshly isolated dendritic epidermal T cells and dendritic epidermal T cell lines expressed mRNA for interferon-gamma. Recent studies indicated that interleukin-18, a novel cytokine which strongly induces interferon-gamma production by T cells, was produced by murine keratinocytes and Langerhans cells. Interleukin-12, which is regarded as a key cytokine for Th1 type helper clone responses, has also been reported to be produced by these cells in murine skin. In this study, we demonstrated by enzyme-linked immunosorbent assay that interleukin-18 and interleukin-12 synergistically upregulated interferon-gamma production by dendritic epidermal T cells in short-term cultures. This was the case in both C57/BL6 mice and BALB/C mice, although the quantity of interferon-gamma produced was different in the two mouse strains. Interleukin-18 or interleukin-12 alone did not induce interferon-gamma production by dendritic epidermal T cells. Interferon-gamma mRNA was only weakly detected by the semiquantitative reverse transcriptase-polymerase chain reaction method in freshly isolated dendritic epidermal T cells, and the mRNA expression was much increased 12 h after stimulation with interleukin-18 and interleukin-12. We also confirmed biologic activity of interferon-gamma produced by dendritic epidermal T cells by showing upregulation of major histocompatibility complex class II expression on Pam 212, murine keratinocyte cell line. Thus, this study suggests that interleukin-18 and interleukin-12 produced by keratinocytes and Langerhans cells regulate interferon-gamma production by dendritic epidermal T cells and thus may play important parts in the regulation of immune responses in skin-associated lymphoid tissues.

Immunocompetent cells in amalgam-associated oral lichenoid contact lesions

Inflammatory cells in amalgam-associated, oral lichenoid contact lesions (OLL) were studied in 19 patients by immunocytochemistry using monoclonal antibodies. Ten of the patients displayed allergic patch test (PT) reactions to several mercury compounds and nine were negative. The immunocytochemical quantification showed a uniform composition of the inflammatory mononuclear cells in the two study groups. The number of HLA-D/DR-positive dendritic cells (P<0.001) and CD1a-positive Langerhans cells (P=0.035) was significantly lower in the PT-negative than PT-positive patients. HLA-D/DR expression on keratinocytes varied from negative to full thickness staining of the epithelium. HLA-D/DR expression in the full thickness of epithelium (3) or through the basal and spinous cell layers (2) was seen in 5 of 8 PT-positive patients, whereas none of the PT-negative patients had this staining pattern (P=0.045). These patients also showed a good clinical response after amalgam removal. Consequently, OLL may represent a true delayed hypersensitivity reaction with a trans-epithelial route of entrance of the metal haptens released from dental restorative materials.

Oral and epicutaneous desensitization in urushiol contact dermatitis in guinea pigs sensitized by 2 methods of different sensitizing potency

This investigation was conducted to study the relationship between the different intensities of sensitization to urushiol induced by the maximization test method (MT) or by the ear-flank method (EF) in guinea pigs, and hyposensitization induced by repeated oral and/or epicutaneous administration of the allergen, and to compare the immune tolerance achieved between these routes of dosing. During the observation period of 10 weeks, both oral and epicutaneous administration produced hyposensitization to urushiol after weak sensitization by EF; however, only combined administrations via the oral and epicutaneous routes achieved hyposensitization after potent sensitization, while inadequate tolerance was induced by oral dosing and none by epicutaneous dosing. Thus, it is indicated that difficulty in establishing immune tolerance may increase with increasing intensity of primary sensitization, and that hyposensitizing potency tends to increase in the order epicutaneous, oral and combined (e.p.+p.o.) administrations of urushiol.

Interferon-gamma-stimulated human keratinocytes express the genes necessary for the production of peptide-loaded MHC class II molecules

Keratinocytes exposed to interferon (IFN)-gamma synthesize major histocompatibility complex class II antigens both in vivo and in vitro; however, the expression of class II accessory genes has not yet been investigated. In this study, we examined the capacity of normal human keratinocytes activated with IFN-gamma to express HLA-DR, HLA-DM, and invariant chain genes as well as two major transcription regulatory genes, class II transactivator and RFX5. Cultured keratinocytes were shown to synthesize low levels of DM alpha, invariant chain p33, and RFX5 transcription factor. Upon treatment with IFN-gamma, expression of RFX5, DM alpha, and invariant chain p33 mRNA increased, whereas class II transactivator mRNA appeared de novo, followed by the expression of DR alpha, DMbeta, and invariant chain p41 genes. Western blot analysis showed that both p33 and p41 invariant chain forms and DM became detectable in keratinocytes after stimulation with IFN-gamma, with a higher p41/p33 ratio compared with Raji B cells. Finally, HLA-DR molecules present on IFN-alpha-treated keratinocytes were shown to be remarkably resistant to sodium dodecyl sulfate denaturation at room temperature, a feature that class II molecules acquire when their groove is properly loaded with peptide. These results suggest that human keratinocytes activated with IFN-gamma possess the biochemical requirements for the generation of functional class II peptide complexes.

Transgenic mice expressing IFN-gamma in the epidermis have eczema, hair hypopigmentation, and hair loss

To study the role of IFN-gamma in the pathogenesis of inflammatory skin diseases, we used the involucrin promoter to overexpress IFN-gamma in the suprabasal layers of transgenic mouse epidermis. IFN-gamma mRNA and protein were readily detectable in the skin but not in the blood. Mice exhibited striking hypopigmentation of the hair due to a reduced abundance of DOPA-positive melanocytes. Severely affected mice had reddened skin, growth retardation, hair loss, and flaky skin lesions. Keratinocyte proliferation was increased, and there was epidermal thickening with spongiosis and parakeratosis. Suprabasal beta1 integrin expression and induction of keratin 17 in interfollicular epidermis provided evidence of perturbed differentiation. IFN-gamma receptor expression was reduced, and there was induction of ICAM-1 and MHC class II molecules on the surface of transgenic keratinocytes. The skin of severely affected mice was characterized by a dermal infiltrate of T lymphocytes and macrophages/monocytes, but the epidermis was almost devoid of Langerhans cells and T lymphocytes. The number of Langerhans cells in the lymph nodes was increased in the transgenics, and autoantibodies to keratinocytes were produced. Transgenic mice showed an increased contact hypersensitivity reaction to topical application of DNFB. We conclude that constitutive IFN-gamma expression in the epidermis results in a form of eczema resembling contact dermatitis and in a profound contact hypersensitivity reaction.

Fixed drug eruption caused by iopamidol, a contrast medium

We report a patient who developed a fixed drug eruption caused by the contrast medium, Iopamidol. We diagnosed it by her episode pattern and the results of patch tests. This substance has not been previously implicated as a cause of fixed drug eruption. Immunohistochemical studies showed Fas expression in keratinocytes of the lesion, but not in the uninvolved skin. This finding may explain the preferential localization of fixed drug eruption.

Characterization of verruciform xanthoma by in situ hybridization and immunohistochemistry

Verruciform xanthoma (VX) is a rare, benign lesion, mainly found in the oral mucosa. Histologically and ultrastructurally, the lesion is characteristic and well defined. However, the etiology of the lesion remains unclear. The purpose of the present study was to elaborate upon the pathogenesis of VX by evaluation of an additional series of oral examples for human papillomaviruses (HPV), using immunohistochemistry and in situ hybridization, and to further characterize the cellular components of VX immunohistochemically. Twelve specimens diagnosed as VX were retrospectively collected. One of the twelve specimens was positive for HPV types 6/11 by in situ hybridization. None of the twelve specimens demonstrated the presence of HPV antigen by immunohistochemistry. By immunohistochemical studies, the predominant cells in the inflammatory infiltrate were T cells. The foam cells were of monocyte/macrophage lineage. S-100-positive (Langerhans) cells were occasionally found in the suprabasal layer of the epithelium. HLA-DR-positive keratinocytes were noted at the intense inflammatory sites. Taken together, these findings suggest that an immune response may play a role, at least in part, in VX pathogenesis.