Role of epidermal Langerhans cells in viral infections

Abstract

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.

Role of Langerhans cells and other dendritic cells in viral diseases

“…An inverse correlation was established between Langerhans cell density at the site of virus inoculation and the severity of HSV-1 disease [102,126,128]. In contrast, activation of Langerhans cells by the immunomodulator, OK-432, was associated with a decrease in morbidity and mortality caused by HSV-1 infection in the skin [129].…”

“…However, prior exposure of the skin to HSV-1 reactivating stimuli somehow enables these microfoci to develop into overt recrudescent lesions [50,51]. It appears that all major HSV-1 reactivating stimuli, including trauma to the skin, hyperthermia, glucocorticoids and UVB irradiation, also impair Langerhans cell function [22,70,102,123,128,152,155]. Thus, inciting stimuli may promote the development of recurrent disease by damaging Langerhans cells which may then be unable to prevent the transformation of subclinical micofoci of infection into recrudescent lesions [102,126,128].…”

“…Viral infections may in fact generate considerable deleterious changes in dendritic Dendritic cells in viral diseases 9 cell structure and function, as illustrated by recent reports on the effects of HIV-1, HPV and molluscum contagiosum virus on dendritic cell state [8,18,27,32,66,83,84,86,111,128,146].…”

“…Similarly, cutaneous infection with HPV was shown to be associated with a marked decrease in Langerhans cell density and with morphological alterations of Langerhans cell ultrastructure at the site of infection [18,128]. Delivery of otherwise immunogenic antigens to a skin area depleted in Langerhans cells is known to be followed by the development of antigen-specific tolerance [23,123].…”

“…Impairment of Langerhans cell and dendritic cell function may contribute to the susceptibility of AIDS patients to opportunistic infections and neoplastic disorders in the skin and elsewhere [128,137]. A correlation has been established between decreased numbers of Langerhans cells in the oral mucosa and the presence of candidal hyphae, Epstein-Barr virus (EBV) and HPV infection in oral hairy leukoplakia (HL), a condition that often heralds full.-blown AIDS [27].…”