Oral mucosal lesions in experimental graft-versus-host disease: morphological and immunohistochemical characterization of infiltrating cells.

To facilitate recognition of the oral mucosal lesion that develops in rats with graft-versus-host disease (GVHD) induced by injecting spleen cells of parental strain rats (Brown Norway) into non-irradiated (Brown Norway x Lewis) F1 hybrid rats, we followed the development of the tongue lesion histologically and immunohistochemically. This assessment revealed an increase in the number of MHC class II+ cells with dendritic shape in the lamina propria to be the earliest stage of the tongue lesions in GVHD rats. The subsequent mononuclear cell infiltration with epithelial cell destruction, characteristic of GVHD, consisted of CD8+ cells and macrophages. Our findings seem to indicate that MHC class II+ cells with dendritic shape may provide antigen presentation in the induction of local immunological responses, including tissue destruction, by CD8+ cells and macrophages in the tongue of GVHD rats.