The ultrastructure of the human epidermis in chronic graft-versus-host disease

The epidermal ultrastructure of 11 allogeneic bone marrow recipients with chronic graft-versus-host disease (GVHD) was compared with that of 4 recipients without chronic GVHD. This electron microscope study revealed three patterns of epidermal injury typical of chronic GVHD. The first type was a nonacantholytic (nondissecting) injury with a prominent cellular infiltrate consisting primarily of lymphocytes accompanied by a few macrophages. The second type was an acantholytic (dissecting) injury with a prominent infiltrate, while the third was a nondissecting injury with a sparse infiltrate. Broad-zone contact was observed between lymphocytes and all epidermal cell types as well as between other lymphocytes and macrophages. Point contact was only observed between lymphocytes and epidermal cells. Lymphocytes appeared to detach desmosomes from adjacent keratinocytes by isolating them with cytoplasmic projections, a phenomenon not previously described. Typical damage to the epidermal cells in the basal and spinous layers consisted of either swelling of the organelles or condensation of the cytoplasm and nucleus. In the keratinocyte, the condensation reaction resulted in the formation of colloid bodies, some of which were phagocytized by macrophages. Besides the cytolytic events, a concurrent stimulatory reaction occurred in the epidermal cells. The number of melanosomes in melanocytes and of Langerhans cell granules and dense bodies in the Langerhans cells all increased. Extensive areas of replication and disruption of the basal lamina were subjacent to areas of necrosis in the basal layer.