T-Cell-Mediated Injury to Keratinocytes: Insights from Animal Models of the Lichenoid Tissue Reaction

A systematic review of case-control studies of cytokines in blister fluid and skin tissue of patients with Stevens Johnson syndrome and toxic epidermal necrolysis

Stevens Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse reactions characterised by keratinocyte apoptosis, necroptosis and epidermal detachment. Several cytokines and cytotoxic proteins have been shown to be elevated in the blood and skin of SJS/TEN sufferers and biologics such as intravenous immune globulin and tumour necrosis factor (TNF)-alpha inhibitors have demonstrated good therapeutic potential. The exact pathogenic model of SJS/TEN however remains elusive. This systematic review aimed to evaluate the case-control studies of cytokines and cytotoxic proteins in the blister fluid and skin of adults with Stevens Johnson syndrome and/or toxic epidermal necrolysis. This review was registered with INPLASY and conducted in accordance with the PRISMA reporting guidelines. Potential bias was assessed using the NIH criteria. Eleven articles describing results from 96 cases and 170 controls were included. Fas, Fas ligand, Interleukin (IL)-8 and B-cell lymphoma (Bcl)-2 were elevated in SJS/TEN blister fluid and skin tissue, compared with healthy controls. IL-2, IL-6, TNF-alpha, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), interferon-gamma and matrix metalloproteinase-2 were elevated in SJS/TEN blister fluid compared with fluid sampled from lesional controls. Granulysin, IL-33, TGF-beta-1 and IL-13 were elevated in SJS/TEN skin tissue compared with lesional lichen planus tissue, as was IL-13, IFN-gamma, IL-2 and IL-5, when compared with erythema multiforme tissue. A wide array of cytokines and cytotoxic proteins are present at higher concentrations in the blister fluid and skin tissue of SJS/TEN patients compared with healthy and lesional controls. Our findings suggest that these proteins may be pathogenic, as well as possibly markers for diagnosis, disease severity and course. They may also prove to be useful therapeutic targets. More research is needed.

Lichen Planus

Lichen planus (LP) is a T cell-mediated disease affecting the stratified squamous epithelia of the skin and/or mucus membrane. Histologically, the disease is characterized by a lichenoid inflammatory infiltrate and vacuolar degeneration of the basal layer of the epidermis. LP has three major subtypes: Cutaneous, mucosal and appendageal LP. Rarely, it may affect the nails in the absence of skin and/or mucosal changes. LP may also be induced by several drugs, typically anti-hypertensive medication or be associated with infections, particularly viral hepatitis. The diagnosis is based on the clinical presentation and characteristic histological findings. Although the disease is often self-limiting, the intractable pruritus and painful mucosal erosions result in significant morbidity. The current first-line treatment are topical and/or systemic corticosteroids. In addition, immunosuppressants may be used as corticosteroid-sparing agents. These, however are often not sufficient to control disease. Janus kinase inhibitors and biologics (anti-IL-12/23, anti-IL17) have emerged as novel future treatment options. Thus, one may expect a dramatic change of the treatment landscape of LP in the near future.

Keratin 17 is Not Always a Marker of Proliferation of Keratinocytes in Skin Diseases

Purpose

Keratin 17 (K17) is an embryonic keratin and overexpression is seen in psoriasis, which is a hyperproliferation skin disease. Nonetheless, whether it is also highly expressed in other proliferative skin diseases remains unclear. The aim of this study is to explore the expression of K17 in cutaneous lichen planus (CLP), lichen simplex chronicus (LSC), and prurigo nodularis (PN).

Methods

A total of 20 skin samples from CLP lesions, 20 from LSC lesions, 20 from PN lesions, and 10 healthy adult skin tissues were obtained. Then, the expression of K17 was analyzed using immunohistochemistry on paraffin-embedded tissue sections. Furthermore, quantitative and semi-quantitative immunohistochemical scores of K17 were independently evaluated under a microscope by 2 dermatologists.

Results

Immunohistochemical analysis revealed that in normal skin, K17 was minimally expressed. Nevertheless, it was highly expressed in all epidermal layers in CLP lesions (P-value <0.01), and negatively expressed in LSC and PN lesions (all P-value >0.05). The average gray value of K17 in CLP was 151.153±13.985 (P-value <0.001), while the average values of K17 in LSC and PN were 178.720±12.001 and 181.316±8.920, respectively (all P-value >0.05).

Conclusion

K17 is potentially expressed in certain inflammatory skin diseases, including psoriasis and lichen planus. Besides, it is not always a marker of hyperproliferation of keratinocytes in skin diseases.

Plasmacytoid Dendritic Cells and Type I Interferon Signature in Lichen Striatus

BACKGROUND/OBJECTIVES

In addition to several infectious and neoplastic cutaneous entities, plasmacytoid dendritic cells (pDCs) have been shown to be involved in the pathogenesis of multiple cutaneous inflammatory and autoimmune disorders, including those characterized histologically by an "interface dermatitis" pattern such as lupus or lichen planus (LP), but their role in lichen striatus (LS), which is also known to have this histologic inflammatory pattern, has never been studied. The objective of the study was to investigate the role of pDCs in LS.

METHODS

Fifteen LS patients were found in our database and were immunohistochemically tested for pDC occurrence and activity using anti-blood-derived dendritic cell antigen-2 and anti-myxovirus resistance protein A (MxA) antibodies, respectively. These individuals were also compared with 15 individuals with LP.

RESULTS

pDCs were present in all individuals with LS and LP, but they were less abundant in those with LS, although MxA (surrogate marker of local type I interferon production and thus an indirect assessment of pDC activity) was similarly intense and diffuse in all individuals with LS and LP. In addition to being part of the upper dermal inflammatory bandlike infiltrate as in LP, LS cases, unlike LP, also showed perieccrine pDCs.

CONCLUSIONS

pDCs constitute a central component of the inflammatory infiltrate in LS, suggesting a significant role in its pathogenesis. pDC distribution (perieccrine distribution) could also help in microscopically differentiating LS from LP.

Wnt5a is involved in the pathogenesis of cutaneous lichen planus

BACKGROUND

Cutaneous lichen planus (CLP) is a chronic inflammatory and immune-mediated disease. Wnt5a is one of the most extensively studied Wnt proteins, and has important functions in stimulating inflammation, cell proliferation, cell fate determination and cell differentiation. Wnt5a expression in CLP has not been comprehensively studied to date.

AIM

To determine the expression and distribution of Wnt5a in CLP.

METHODS

Skin samples were obtained from patients with CLP and healthy controls (HCs). The WNT5A gene was detected by real-time quantitative PCR, and Wnt5a protein by immunohistochemical analysis and western blotting.

RESULTS

WNT5A mRNA was upregulated in CLP samples compared with the HC skin samples (P < 0.001). Wnt5a protein was overexpressed in all layers of the epidermis and dermis in CLP lesions compared with HC skin (all P < 0.001). These results were confirmed by western blotting.

CONCLUSIONS

The data presented in this study suggest that Wnt5a pathway may play an important role in the pathogenesis of CLP.

Emerging role for the killer-cell immunoglobulin-like receptors genotype, in the susceptibility of skin diseases

NK cells are a major group of immune cells responsible for the phenomenon of natural, innate cytotoxicity. One of the better studied receptors of human NK cells are killer cell immunoglobulin-like receptors (KIR) responsible for checking the presence of MHC class I molecules, which serve as their ligands. Although previously treated as specific for NK cells, nowadays these receptors are known to also occur on T cells. Genetics of KIR molecules is very complicated, what create a great variability of haplotypes in various populations world-wide. In addition, some KIR are known to recognize HLA-C (epitopes C1 or C2), HLA-B (Bw4) or HLA-A (A3 and/or A11) molecules. Therefore, this makes a huge diversity of reactions among individuals, depending on the presence or absence of given KIR and their ligands, hence differential susceptibility to several diseases, including various dermatoses. This paper underlines the important role of both KIR genotypes and HLA class I genes with reference to the various skin diseases.

Immunoregulatory molecule B7-H1 (CD274) contributes to skin carcinogenesis

B7-H1 (CD274), a member of the B7 family of coinhibitory molecules, is often induced in human tumors and its expression is closely correlated with a poor prognosis or higher malignancy grade. Tumor-associated B7-H1 is implicated in mechanisms of immune escape. Under inflammatory conditions, B7-H1 is also inducible in normal epithelial cells, but little is known about its involvement in the conversion of normal cells to tumor cells. We recently found that skin-specific expression of B7-H1 accelerates chemically induced carcinogenesis of squamous cell carcinoma (SCC), despite impaired skin inflammatory responses, in B7-H1 transgenic (B7-H1tg) mice. B7-H1tg-derived keratinocytes (KC) and SCCs exhibited a marked reduction of E-cadherin, and B7-H1tg-originated SCCs showed elevated expression of the transcription factors Slug and Twist, suggesting that B7-H1 overexpression in KCs promotes the epithelial-mesenchymal transition and accelerates carcinogenesis. This review discusses the diverse functions of B7-H1 in carcinogenesis and cancer progression, and considers future directions for developing cancer therapy targeting B7-H1.

Salivary and plasma levels of Toll-like receptor 2 and Toll-like receptor 4 in chronic periodontitis

BACKGROUND

This cross-sectional study was planned to investigate whether patients with chronic periodontitis exhibit different salivary or plasma concentrations of Toll-like receptor (TLR) 2 and TLR4 compared to subjects who are clinically healthy.

METHODS

Whole saliva and plasma samples were obtained and full-mouth clinical periodontal measurements were recorded from 22 otherwise healthy patients with chronic periodontitis and 21 systemically and periodontally healthy control subjects. Salivary and plasma TLR2 and TLR4 levels were determined by enzyme-linked immunoassays. Data were tested statistically using Mann-Whitney U test.

RESULTS

The healthy group exhibited significantly lower values in all clinical measurements (P <0.001). The salivary TLR2 levels were similar in the two study groups (P >0.05). The patients with chronic periodontitis exhibited significantly higher salivary TLR4 (P <0.01) and plasma TLR2 and TLR4 levels (P <0.05).

CONCLUSION

The present findings support a hypothesis that inflammation increases expression of TLRs which leads to an increased detection of TLRs in saliva and plasma, which could be useful as a diagnostic test for periodontal diseases.

Soluble forms of Toll-like receptor 4 are present in human saliva and modulate tumour necrosis factor-alpha secretion by macrophage-like cells

In health, mucosal inflammation is prevented by tightly regulated responses via Toll-like receptors (TLR) that interact with specific microbe associated molecular patterns. Currently, 13 TLRs have been identified. Based on the specificity of ligand recognition, TLR-2 and TLR-4 can recognize most oral commensal microorganisms. Recent identification of some soluble TLRs (sTLRs) suggests additional regulatory roles for these receptors. We report here the presence of sTLR-4 polypeptides in adult human saliva. Functionally, the salivary sTLR-4 suppressed cytokine secretion by activated macrophages. The sTLR-4 levels were elevated significantly in oral lichen planus (OLP), a chronic inflammatory condition of the oral mucosa characterized by clinical persistence. In contrast, the epithelial cells in the saliva of OLP subjects expressed significantly reduced TLR-2 and TLR-4 mRNA that correlated with fewer bacteria/salivary epithelial cells. Investigating the soluble and cellular components of saliva is useful in identifying potential biomarkers for oral mucosal lesions.