Absence of Langerhans cells in oral hairy leukoplakia, an AIDS-associated lesion

Oral hairy leukoplakia (HL) is a recently described manifestation of human immunodeficiency virus (HIV) infection in which Epstein-Barr virus (EBV) has been shown to replicate. To seek evidence for a local defect in mucosal immunity, we assessed the presence of epithelial Langerhans cells (LC) in these lesions and in autologous nonlesional mucosa. We used monoclonal antibodies against HLA-DR, HLA-DQ, and T6 antigens to identify LC in biopsy specimens of HL from 23 homosexual men. In all lesion specimens, LC either were not detected or were present only in greatly reduced numbers with at least 1 of the antibodies. In nonlesional oral mucosa from the same patients, LC were detected with all 3 antibodies in 11/12 specimens (92%) and were found in approximately normal numbers with at least 1 antibody. There was close correlation between the absence of LC and positive staining for EBV, human papillomavirus antigens, and candidal hyphae in the epithelium. We conclude that LC are absent or greatly reduced in the lesions of HL. Absence of normal LC function may be important in the pathogenesis of HL and may reflect an event in the pathogenesis of other features of the acquired immune deficiency syndrome.