Etretinate suppresses ICAM-1 expression by lesional keratinocytes in healing cutaneous lichen planus

Update on oral lichen planus: etiopathogenesis and management

Lichen planus (LP) is a relatively common disorder of the stratified squamous epithelia, which is, in many ways, an enigma. This paper is the consensus outcome of a workshop held in Switzerland in 1995, involving a selection of clinicians and scientists with an interest in the condition and its management. The oral (OLP) eruptions usually have a distinct clinical morphology and characteristic distribution, but OLP may also present a confusing array of patterns and forms, and other disorders may clinically simulate OLP. Lesions may affect other mucosae and/or skin. Lichen planus is probably of multifactorial origin, sometimes induced by drugs or dental materials, often idiopathic, and with an immunopathogenesis involving T-cells in particular. The etiopathogenesis appears to be complex, with interactions between and among genetic, environmental, and lifestyle factors, but much has now been clarified about the mechanisms involved, and interesting new associations, such as with liver disease, have emerged. The management of lichen planus is still not totally satisfactory, and there is as yet no definitive treatment, but there have been advances in the control of the condition. There is no curative treatment available; immunomodulation, however, can control the condition. Based on the observed increased risk of malignant development, OLP patients should be offered regular follow-up examination from two to four times annually and asked to report any changes in their lesions and/or symptoms. Follow-up may be particularly important in patients with atrophic/ulcerative/erosive affections of the tongue, the gingiva, or the buccal mucosa. Much more research is required into the genetic and environmental aspects of lichen planus, into the premalignant potential, and into the possible associations with chronic liver, and other disorders. More clinical studies are required into the possible efficacy of immunomodulatory drugs such as pentoxifylline and thalidomide.

Immunologic aspects of dermal and oral lichen planus: a review

There have been many investigations, both experimental and epidemiologic, of the forms of LP affecting the skin and oral mucosae. These studies have provided a varied range of hypotheses to explain not only the factors determining susceptibility to and onset of this disease, but also the immunologic mechanisms leading to the pathosis with which LP is associated. Much progress has been made, especially through in vitro studies, regarding detailed aspects of the immunology of LP. However, data is often conflicting or incomplete. In this review we attempt to bring together the currently available data regarding the immunologic basis of LP.

Expression of monocyte/macrophage markers (CD13, CD14, CD68) on human keratinocytes in healthy and diseased skin

The results of several investigations proved that, in special circumstances, human keratinocytes (HKs) synthesize and express cell surface moieties characteristic of effector and/or accessory cells of the immune system, such as CD16, CD36, HLA-DR, and intercellular adhesion molecule-1 (CD54), which are all detectable on the surfaces of macrophages. In the present study, skin biopsies from healthy volunteers, from positive tuberculin skin tests, and from patients with acute urticaria (AU), lichen planus (LP), psoriasis vulgaris (PV), mycosis fungoides (MF), and purpura pigmentosa chronica (PPC) were investigated by means of a multistep immunoperoxidase method to examine the reactivity of the HKs with a panel of monoclonal antibodies (MABs) characteristic of monocyte/macrophage cell lines. In biopsies obtained from positive tuberculin tests and from clinically involved skin of patients with LP, PV, MF, or PPC, a multifocal, positive peroxidase reaction was observed on the membranes of HKs of the basal and suprabasal cell layers when the MABs OKM13 (CD13), OKM14 (CD14), and Dako-Macrophage (CD68) were used. In contrast, specific staining of the HKs was not observed with the same antibodies in the biopsies of healthy volunteers or of patients with AU or in the uninvolved skin specimens obtained from the other patients. The HKs of PV, LP, MF, PPC, and AU patients and those of the healthy subjects all failed to give positive reactions when MABs against CD11b, CD15, or CD33 were used. The published data supplement the known surface characteristics of HKs, reflecting their stage of activation and differentiation.

Electron microscopic study on cell-to-cell interactions in oral lichen planus

Ultrastructural analysis of oral lichen planus was performed in 18 cases, focusing on cell-to-cell interactions. In the peripheral portion of the lesion, the most consistent findings were a widening of intercellular spaces, separation of the basement membrane (BM) from basal cells and scarce inflammatory cells. In the central portion of the lesions basal cells and BM showed severe damage and numerous inflammatory cells infiltrated into both the epithelium and subepithelial stroma. The infiltrates predominantly consisted of T-lymphocytes, a few Langerhans cells (LC) and macrophages. Most lymphocytes were large and positive for CD45RO. Dendritic LC and macrophages with cytoplasm containing abundant organelles were seen in the epithelium and subepithelial stroma, respectively. Close contacts of lymphocytes with LCs, macrophages and also with keratinocytes were sometimes observed in the central portion. In the subepithelial stroma, some lymphocytes contacted an HLA-DR+ dendritic cell, which was possibly a macrophage, forming a rosette-like arrangement. Conjugations between CD4 cells and dendritic cells (possibly LC) and also between CD8 cells and basal cells were observed in the epithelium. These T cells were large in size, and the CD8 cells which made contact with degenerated keratinocytes possessed cytoplasm containing numerous polarized organelles and a nucleus toward and contrary to the contact side, respectively. These lymphocytes expressed LFA-1 on the cell surface, and many basal cells exhibited ICAM-1. These findings indicate that T cells may receive information from LC and macrophages concerning degenerative keratinocytes, and that informed T cells attack perhaps the keratinocytes.

Immune-associated surface markers of human keratinocytes

The results of a number of investigations have proved that human keratinocytes (HKs) possess the ability to synthesize and express cell surface moieties characteristic of effector and/or accessory cells of the immune system. The present paper summarizes the known immune cell surface features of HKs, reflecting their stage of activation and differentiation. The surface and functional characteristics of HKs suggest their monocyte/macrophage behavior, which fits in well with the presumed active involvement of HKs in the skin immune system.