Does HIV disease progression influence epidermal Langerhans cell density?

Langerhans cells (LC) are antigen-presenting CD4+ dendritic cells in the skin which may become infected by the human immunodeficiency virus (HIV). Decreased LC function could account for the cutaneous manifestations seen in HIV disease. Previous studies of epidermal LC density in HIV-infected subjects have produced conflicting results. A definitive, prospective, case-control study was performed to determine whether there is an association between epidermal LC density and HIV clinical disease stage. Skin cryosections were stained with the CD1 monoclonal antibody using a three-step immunoperoxidase method. LC were counted by light microscopy and epidermal dimensions calculated with computer-assisted planimetry. The stage of the HIV clinical disease correlated with epidermal LC densities was quantified by three different methods: mean LC numbers per mm length of basement membrane, mean LC per mm2 of epidermal area, and mean LC population per mm of epidermal surface length. Seventy-one subjects, recruited from a large out-patient HIV clinic in London, comprised 56 HIV-positive men and 15 male HIV-negative controls. Contrary to previous smaller studies, there was no detectable association between epidermal LC density (quantified by any of the three methods) and the stage of the HIV clinical disease. Given that HIV infects large numbers of CD4+ cells, we propose possible hypotheses to account for the apparent preservation of static LC numbers in the skin. Further studies of LC kinetics and function are required to elucidate their role in the natural history of HIV infection.