Ultrastructural studies of spontaneously regressing plane warts. Langerhans cells show marked activation

Diseases associated with human papillomavirus infection

Human papillomaviruses (HPVs) are ubiquitous, well adapted to their host and cleverly sequestered away from immune responses. HPV infections can be productive, subclinical or latent in both skin and mucosa. The causal association of HPV with cervical cancer, and increasingly with rising numbers of squamous cell carcinomas at other sites in both men and women, is increasingly recognised, while the morbidity of cutaneous HPV lesions, particularly in the immunosuppressed population is also significant. This chapter sets out the range of infections and clinical manifestations of the consequences of infection and its persistence and describes why HPVs are both highly effective pathogens and carcinogens, challenging to eliminate.

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.

Clinical, histopathologic, and molecular aspects of cutaneous human papillomavirus infections

Human papillomaviruses comprise a large family of double stranded DNA viruses that are the etiologic agents of benign warts and anogenital cancers. At least 82 different human papillomavirus types have been identified and many remain yet uncharacterized. The development of new molecular techniques in recent years has led to an increased understanding of human papillomaviruses and their roles in carcinogenesis. Several clinicopathologic entities arising from human papillomavirus infection encountered by the dermatologist are the subject of the article. The epidemiology, molecular biology, clinical presentation, histologic findings, and treatment of each disorder, where applicable, is discussed.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.

Role of epidermal Langerhans cells in viral infections

Langerhans cells function as highly potent antigen-presenting cells in the epidermis. In the last few years, their role in viral infections has been studied in various experimental systems. They have been shown to be involved in the pathogenesis of a number of infections of viral origin. These include vaccinia virus, human papilloma virus, herpes simplex virus, foot and mouth disease virus and human retrovirus infections. Studies on the effect of various factors, that are known to modulate the activity and density of Langerhans cell in the epidermis, may lead in the future to the development of new strategies aimed at inhibiting virus infections or even eradicating latent infection.

Epidermal Langerhans cells, dermal dendritic cells, and keratinocytes in viral lesions of skin and mucous membranes: an immunohistochemical study

We wanted to evaluate the eventual expression of viral antigens and MHC class II products by keratinocytes as well as the alterations of epidermal Langerhans cells and dermal dendritic cells in viral lesions of skin and mucous membranes. Therefore we investigated 68 biopsy specimens of protracted viral lesions, such as warts, condylomas, and mollusca contagiosa, and of rapidly resolving viral lesions such as herpes simplex virus infection. For this we used immunohistochemical staining techniques and several monoclonal and polyclonal antisera. In most cases investigated viral antigens (human papilloma virus antigens or herpes simplex virus type 1 antigens) could be demonstrated in keratinocytic nuclei. Except for a few viral lesions in which epidermal Langerhans cells were rather numerous, epidermal Langerhans cells were reduced in number or absent in almost all viral lesions. Moreover, epidermal Langerhans cells and dermal dendritic cells showed changes in morphology, distribution, and immunophenotype. These alterations may be caused by a toxic effect of the virus on dendritic cells. HLA-DR+ keratinocytes could be identified in few viral lesions only; HLA-DQ+ keratinocytes were not seen. Possible explanations for this lack of MHC class II expression by keratinocytes are discussed.

Does radiation-induced abrogation of skin Langerhans cell functions lead to enhanced incidence of skin tumors in patients with genetic disorders of DNA repair?

A hypothesis is presented which states that persons with the genetic disorders xeroderma pigmentosum and ataxia-telangiectasia, manifested by a deficiency of DNA repair, develop cutaneous tumors due to the elimination of reticuloendothelial system cells (Langerhans cells) in the skin, and the subsequent loss of control of epidermal cellular elements.

Primary tissue culture of spontaneously regressing flat warts. In vitro attack by mononuclear cells against wart-derived epidermal cells

Although tumors may be resolved due to host immune response, it is difficult to obtain direct evidence of this in man. Numerous flat warts, human papilloma virus type 3-induced papillomas, disappear systemically and simultaneously after showing inflammatory changes. Histologically, there is a dense cellular infiltration composed of lymphocytes and mononuclear phagocytes as identified by alpha-naphthyl acetate esterase staining in situ, the former being predominant in most cases. The primary tissue culture of such inflamed flat warts from ten cases revealed a proliferation of wart-derived keratinocytes as is the case with ordinary flat warts. However, in nine of the ten cases, massive mononuclear cells, most of which were T-lymphocytes, migrated out of the explants and began to attack these keratinocytes, inducing degenerative changes. These findings indicate that cell-mediated tumor cell destruction rather than antiviral reaction induces systemic spontaneous regression of multiple papillomas in man.

Cervical healing and Langerhans' cells

A study of cervical epithelium healing after laser treatment found the early presence of Langerhans' cells. These cells were demonstrated using a histochemical technique for adenosine triphosphatase. The significance of Langerhans' cells in healing epithelium and their probable immunological role is discussed.

What's new in dermatopathology?

This review emphasizes the important work in dermatopathology reported in the past 3 years. In reviewing the recent contributions in the field, four areas appear to have received particular attention: (1) new information concerning the histogenesis of cutaneous tumors based on the dual functional capacities of cells; (2) the Langerhans cell and its role in inflammatory and neoplastic processes; (3) prognostic factors in stage I malignant melanoma; and (4) the use of new immunofluorescent and immunohistochemical technics as diagnostic tools in cutaneous pathology.

Langerhans' cells in human cervical epithelium: effects of wart virus infection and intraepithelial neoplasia

The distribution of Langerhans' cells and T and B lymphocytes in cervical epithelium affected by wart virus infection (WVI) and intraepithelial neoplasia (CIN) has been studied by immunohistological techniques with a panel of monoclonal antibodies. In comparison with normal tissue epithelium infected by wart virus consistently showed a partial depletion or absence of both Langerhans' cells and T lymphocytes. The few Langerhans' cells which remained showed loss of their normal dendritic processes and were confined to the vicinity of the basement membrane. In contrast, epithelium from patients with CIN showed an increase in spindle-shaped Langerhans' cells associated with increased numbers of stromal and intraepithelial lymphoid cells. These findings suggest that there is a marked difference in host immune responses in these two conditions and may explain why WVI tends to persist in the epithelium while CIN is often associated with a lymphoid reaction.

T-cell subsets and Langerhans cells in wart lesions

The presence of T-lymphocytes and Langerhans cells was assessed on tissue sections of 28 human warts from various localizations and in normal epidermis by indirect immunofluorescence using specific monoclonal antibodies. In most cases, the density of Langerhans cells was dramatically reduced in wart epidermis as compared to normal epidermis and a mild cellular infiltrate could be noted. In some lesions, OKT4 and OKT8 cell populations were present and the number of Langerhans cells was high both in dermis and epidermis. These data are compatible with the role of Langerhans cells and the existence of a local cellular immune reaction in human papilloma virus-infected tissues. No correlation could yet be established with the virus type on the skin localization.

Langerhans cells in granulomatous syphilis

In a case of granulomatous syphilis (transitional state between early and late syphilis), several Langerhans cells (LC) were present in the basal and medial part of the epidermis. Evidence of LC activation was given by the presence of many Langerhans granules, vesicles, a large Golgi apparatus and, sometimes, Golgi complexes. In some LC, signs of degeneration were visible. Langerhans granules surrounded by cytoplasmic material were present in the intercellular space of the epidermis. Apposition of lymphocytes to LC in the dermal space supports the role of LC in immunologic mechanisms. This was further confirmed by signs of phagocytosis in LC. The interaction of LC with intra-epidermal microorganisms (as, for instance, the Treponema pallidum) might be important in the development of the epidermotropic infiltration. This mainly consists of lymphocytes, which sometimes form a pseudolymphoma. A correlation between LC and granuloma formation is suggested.

Ultrastructural studies of spontaneously regressing plane warts. Macrophages attack verruca-epidermal cells

Plane warts were examined at the earliest phase of spontaneous involution using an electron microscopy. Macrophages outnumbered lymphocytes in invading the epidermis. Lymphocytes exhibited pseudopods on the surface which occasionally reached into the epidermal cells. The cell membranes of both macrophages and epidermal cells frequently disappeared on the contacting surface and on occasion part of the cytoplasm and even the nucleus of macrophages invaded the epidermal cells. The macrophages showed an independent partial loss of their cell membranes with a subsequent outpour of their contents. This ultrastructural feature indicates that in spontaneously regressing plane warts the depressed membrane stability of macrophages as observed in BCG and other-induced tumor cell destruction also occurs in the presence of lymphocytes. Therefore, the spontaneous involution may represent a rejection phenomenon.