OBJECTIVE: The purpose of this study was to elucidate the pathogenesis of oral candidiasis, a common cause of discomfort and social impairment among HIV-infected individuals. STUDY DESIGN, MATERIALS AND METHODS: The oral mucosal immune system cells were analysed by immunohistochemistry and electron microscopy in biopsies from five erythematous and four pseudomem-branous candidiasis cases and were compared with those from seven HIV-positive and 10 HIV-negative controls without candidiasis. RESULTS: The superficial lamina propria and basal epithelial layer was populated by CD1a+ Langerhans cells with infiltration of CD8+ lymphocyteS. Within the submu-cosa are CD36+ dendritic macrophages and lymphocytes, although CD4+ subsets were absent from the infiltrate. The expression of human leukocyte antigen system, DR locus (HLA-DR) and leukocyte specific adhesion molecules was low in erythematous, yet more marked in pseudomembranous candidiasiS. In the pseudomembra-nous form, CD14+ leukocytes were found in the basal epithelial layer. Langerhans cells were significantly more numerous and were richer in dendrites and Birbeck granules in erythematous than in pseudomembranous can-didiasis. CONCLUSIONS: Candidiasis is associated with alterations in the number and differentiation of lymphocytes and dendritic cells, being more severe in the pseudo-membranous than erythematous form. We propose that these alterations play a role in the pathogenesis and evolution of the disease.
