Characterization of the T cell response in allergic contact dermatitis caused by corticosteroids

Gamma/Delta Phenotype in Primary Cutaneous T-cell Lymphomas and Lymphoid Proliferations: Challenges for Diagnosis and Classification

Primary cutaneous T-cell lymphomas pose a diagnostic challenge for dermatopathologists, hematopathologists, and general surgical pathologists. Recognition of gamma/delta phenotype in cutaneous T proliferations has been enhanced by the availability of antibodies against TCRgamma and delta for immunohistochemistry. Thus, reporting gamma/delta phenotype in a cutaneous T-cell lymphoid proliferation may indicate a significant change in therapy and a challenge for dermatologists and oncologists who treat these patients. Herein, we discuss primary cutaneous gamma/delta T-cell lymphoma, its differential diagnosis, and other skin lymphoid proliferations that may show gamma/delta phenotype. Awareness of the occurrence of gamma/delta phenotype in both T-cell lymphomas and benign lymphoid proliferations involving skin is crucial for a better interpretation of histopathologic findings. Integration of clinical presentation, morphology, immunoprofile, and molecular findings is key for a correct diagnosis and appropriate therapy of lesions displaying gamma/delta T-cell phenotype.

Dissecting the complexity of γδ T-cell subsets in skin homeostasis, inflammation, and malignancy

γδ T cells are much less common than αβ T cells, accounting for 0.5% to 5% of all T lymphocytes in the peripheral blood and lymphoid tissues in mice and humans. However, they are the most abundant T-lymphocyte subset in some epithelial barriers such as mouse skin. γδ T cells are considered innate lymphocytes because of their non-MHC restricted antigen recognition, as well as because of their rapid response to cytokines, invading pathogens, and malignant cells. Exacerbated expansion and activation of γδ T cells in the skin is a common feature of acute and chronic skin inflammation such as psoriasis and contact or atopic dermatitis. Different γδ T-cell subsets showing differential developmental and functional features are found in mouse and human skin. This review discusses the state of the art of research and future perspectives about the role of the different subsets of γδ T-cells detected in the skin in steady-state, psoriasis, dermatitis, infection, and malignant skin diseases. Also, we highlight the differences between human and mouse γδ T cells in skin homeostasis and inflammation, as understanding the differential role of each subtype of skin γδ T cells will improve the discovery of new therapies.

Effect of trichloroacetaldehyde on the activation of CD4+T cells in occupational medicamentosa-like dermatitis: An in vivo and in vitro study

Occupational medicamentosa-like dermatitis induced by trichloroethylene (OMLDT) is a hypersensitivity disease with autoimmune liver injury, which has increasingly become a serious occupational health problem in China. However, the pathogenesis of OMLDT remained undefined. In this study, 30 TCE-induced OMLDT patients, 58 exposure controls, and 40 non-exposure controls were recruited. We showed that the ratio of activated CD4⁺ T cells (downregulation of CD62 L) was dramatically increased in OMLDT patients compared to exposure and non-exposure control, suggesting that CD4⁺ T cells activation was a key cellular event in the development of OMLDT. In parallel, the expression of cytokine including IL-2, IFN-γ, TNF-α and IL-17A were increased obviously and IL-4 decreased in CD4⁺ T cells from OMLDT patients. in vitro assay, we found that trichloroethylene metabolites trichloroacetaldehyde (TCAH), not trichloroacetic acid (TCA) or Trichloroethanol (TCOH) could activate the naïve CD4⁺ T cells characterized by a rise in intracellular calcium, down-regulated CD62 L and subsequently trigger the secretion of IL-2, IFN-γ and TNF-α. Notably, the phosphorylation status of NF-κB and p38MAPK were elevated in OMLDT patients. Moreover, TCAH also could activate the p38MAPK and NF-κB, suggesting the role of p38MAPK and NF-κB pathways in the activation of CD4⁺ T cells. In addition, we found that the inhibition of Schiff base formation decreased the ability of TCAH to induce the activation of naïve CD4⁺ T cells and p38MAPK and NF-κB pathway. In conclusion, we revealed that the CD4⁺ T activation and increased the cytokines including IL-2, IFN-γ and TNF-α but decreased IL-4 in CD4⁺ T cells were associated with OMLDT. TCAH could activate naïve CD4⁺ T cells through NF-κB and p38MAPK activation induced by Schiff base formation, which might contribute to the development of OMLDT. These findings provide a new insight into the pathogenesis of OMLDT.

Anti-human Interleukin(IL)-4 Clone 8D4-8 Cross-Reacts With Myosin-9 Associated With Apoptotic Cells and Should Not Be Used for Flow Cytometry Applications Querying IL-4 Expression

Interleukin(IL)-4 is produced by T cells and other leukocytes and is a critical mediator of monocyte and B cell responses. During routine flow cytometry panel validation for the investigation of intracellular cytokines, we observed unique IL-4 expression patterns associated with the widely available monoclonal antibody 8D4-8. Namely, IL-4 (8D4-8) expression was observed in the absence of cellular activation and enhanced following staurosporine exposure. Mass spectrometry analysis of immunoprecipitates from peripheral blood lymphocytes (PBL) revealed that 8D4-8 cross-reacts with the ubiquitous cytoskeletal protein myosin-9. We confirmed these results by western blotting immunoprecipitates, using immunofluorescence among staurosporine-treated Caco-2 cells, and by surface-labeling PBL for 8D4-8 and myosin-9 and analyzing by flow cytometry. Although previously reported from several independent groups, we found no evidence to support the hypothesis that IL-4 is produced by apoptotic cells. Rather, this appears to have been myosin-9. Our data indicate clone 8D4-8 should not be used in the flow cytometric study of IL-4. Furthermore, our work calls for a reevaluation of previous flow cytometric studies that have used this clone for IL-4 analysis and highlights the importance of validation in antibody-based assays.

Novel cutaneous mediators of chemical allergy

Chemical allergy can manifest into allergic contact dermatitis and asthma and the importance of skin sensitization in both of these diseases is increasingly being recognized. Given the unique characteristics of chemical allergy, coupled with the distinct immunological microenvironment of the skin research is still unraveling the mechanisms through which sensitization and elicitation occur. This review first describes the features of chemical sensitization and the known steps that must occur to develop a chemical allergy. Next, the unique immunological properties of the skin - which may influence chemical sensitization - are highlighted. Additionally, mediators involved with the development of allergy are reviewed, starting with early ones - including the properties of haptens, skin integrity, the microbiome, the inflammasome, and toll-like receptors (TLR). Novel cellular mediators of chemical sensitization are highlighted, including innate lymphoid cells, mast cells, T-helper (T_H) cell subsets, and skin intrinsic populations including γδ T-cells and resident memory T-cells. Finally, this review discusses two epigenetic mechanisms that can influence chemical sensitization, microRNAs and DNA methylation. Overall, this review highlights recent research investigating novel mediators of chemical allergy that are present in the skin. It also emphasizes the need to further explore these mediators to gain a better understanding of what makes a chemical an allergen, and how best to prevent the development of chemical-induced allergic diseases.

Allergic Contact Dermatitis Evaluation: Strategies for the Preschooler

PURPOSE OF REVIEW

The environment for the developing children is complex as they are exposed to a variety of activities and settings where potential environmental allergens may be encountered. Recent evidence supports the clinical benefit of patch testing young children suffering from recalcitrant dermatitis. While patch testing has been recently approved by the Food and Drug Administration in children ages 6-18 years old, patch testing strategies for young children of preschool age (between 2 and 6 years old) have yet to be defined.

RECENT FINDINGS

Allergic contact dermatitis is underdiagnosed among pediatric patients, particularly those suffering from concomitant atopic dermatitis as the interplay between the two diseases is complex. Recent reports in literature supported the clinical value, safety, and efficacy of patch testing pediatric patients. This review provides an overview of specific pediatric allergens, special considerations, practical modifications, and systematic exposure-driven guidance approaches toward patch testing preschoolers.

Mechanisms of carcinogenesis in human skin against the background of papillomavirus infection

The cells in the skin tumor developing under conditions of persisting papillomavirus infection are morphologically identical to blast cells in a blood smear from a leukemia patient. The cells filling the lesion focus are morphologically and immunohistochemically related to blood stem cells. A mechanism of epithelial layer modification under conditions of papillomavirus infection leading to carcinogenesis is proposed. The dynamics of structural changes in the skin is characterized by disturbed interactions between the epithelium and adjacent connective tissue, destruction of the basal membrane, disorders in the cambial keratinocyte differentiation, and absence of the spinous and granular layers. We conclude that detection of blast leukocytes in the human skin lesion can be explained by disorders in the cell-cell interactions in the epithelium-mesenchymal tissue system. High proliferative activity followed by death of cambial keratinocytes, migration of effector antigen-presenting CD68 cells to the adjacent connective tissue are the factors inducing migration of blast leukocytic forms to the focus. Not only keratinocyte restitution capacity, but also epithelium-dependent differentiation of young leukocytes disappeared. Undifferentiated cells are migrated from the blood to the epithelium alteration zone, but not in the reverse direction. The insufficiency or the absence of blood blast cell differentiation of the in the focus of epidermal injury and adjacent tissue triggers carcinogenesis. The authors suggest their model of carcinogenesis. The conclusions offer a new concept of cancer pathogenesis and suggest a new strategy in the search for methods for early diagnosis of carcinogenesis.

Improvement of psoriasis during glucagon-like peptide-1 analogue therapy in type 2 diabetes is associated with decreasing dermal γδ T-cell number: a prospective case-series study

BACKGROUND

A few case reports suggest that incretin-based therapies could improve psoriasis in patients with type 2 diabetes, the mechanism(s) of which remain unclear.

OBJECTIVES

To determine the effects after 16-20 weeks of treatment with a glucagon-like peptide (GLP)-1 analogue on clinical severity and histopathological aspects of psoriasis in patients with type 2 diabetes, and to examine the presence of γδ T cells and the expression of interleukin (IL)-17 in psoriasis before and after treatment.

METHODS

Seven patients with type 2 diabetes and psoriasis were followed. Psoriasis Area and Severity Index (PASI) was measured at baseline (T0) and after 7 ± 1 (T1) and 18 ± 2 (T2) weeks' treatment with exenatide/liraglutide. The histopathological pattern of psoriasis, and flow cytometry and immunological data (γδ T-cell percentage and IL-17 expression) were obtained from psoriatic and control sites.

RESULTS

The mean PASI decreased from 12·0 ± 5·9 to 9·2 ± 6·4 (P = 0·04). Histological analysis showed a reduction in epidermal thickness after treatment. The dermal γδ T-cell percentage was higher in psoriatic lesions than in control specimens (P = 0·03), as was IL-17 expression (P = 0·018). A reduction of γδ T cells from 6·7 ± 4·5% to 2·7 ± 3·8% (P = 0·05) was demonstrated in the six patients with improved/unchanged PASI. A correlation between PASI and γδ T-cell percentage evolution during therapy (T2-T0) was noted (r = 0·894, P = 0·007). IL-17 was reduced in the four patients with the highest PASI reductions.

CONCLUSIONS

The administration of a GLP-1 analogue improved clinical psoriasis severity in patients with type 2 diabetes. This favourable outcome was associated with a decrease of dermal γδ T-cell number and IL-17 expression. Further studies are needed to establish long-term efficacy in (diabetic) patients with psoriasis.

Distribution of antigen-presenting cells CD68 in papillomavirus infection in the skin

We analyzed local reactions of immune homeostasis in the human skin, in particular, effector immune cells CD68 responsible for antigen presentation, during human papillomavirus infection. Under conditions of long-term papillomavirus infection, CD68 markers were identifi ed only in the connective tissue of the skin (derma) and were completely absent in the epidermis, where they were found during physiological and reparative regeneration after thermal injury. We concluded that hypertrophy of the epidermis and connective tissue of the dermal papillary layer in human papillomavirus infection is related to the absence of CD68 immune cells in the epithelial plate and their accumulation in the connective tissue adjacent to the basement membrane of the epidermis. The possibility of epithelium contamination with the virus depends on local immune homeostasis. Therefore, induction of proper CD68 distribution in appropriate structures can contribute to normalization of epithelial-connective tissue interactions.