Abstract
CD1a+ epidermal Langerhans cells (ELCs) are depleted during graft-versus-host disease (GVHD) in humans. However, the mechanism of CD1a+ cell depletion in GVHD remains obscure. The aim of the present study was to elucidate the sequential evolution of the ultrastructure of ELCs in experimental acute GVHD. The B10.D2→DBA/2 (900 cGy) strain combination was used for studies of CD4+ T-cell-mediated GVHD (n=3), whereas the B10. BR→CBA (800 cGy) strain combination was used for studies of CD8+ T-cell-mediated GVHD (n=3) . In CD4+ T-cell-mediated GVHD, Birbeck granules in ELCs started to decrease at day 7 and were not detectable after day 14. The numbers of Golgi apparatuses and related vesicles were also decreased, while rough endoplasmic reticulum, ribosomes, and vacuolated mitochondria were increased after day 14. In contrast to CD4+ T-cell-mediated GVHD, in which tumor necrosis factor-α is an essential cytokine, CD8+ T-cellmediated GVHD caused only slight changes in ELCs and tumor necrosis f actor-α seemed to be irrelevant. These data suggest that most ELCs do not migrate into the dermis immediately after the onset of GVHD but remain within the epidermis at least until day 14 and presumably beyond.
