Epidermal allografts.

The epidermis is the sheet of stratified epithelial cells covering the dermal connective tissues. In addition to the epithelial cells (known as keratinocytes) there exist within the epidermis two populations of migratory leukocytes: the class II-positive, dendritic Langerhans' cell, and gamma-delta receptor-positive T lymphocytes. Allografts consisting essentially of epidermis have been in use since the introduction of "pinch" grafts by L. Reverdin in 1872. However, the capacity to culture keratinocytes in vitro to produce sheets of stratified epithelial cells has opened new possibilities. Cultured keratinocyte layers are devoid of passenger leukocytes and were initially widely believed not to be susceptible to rejection. This, however, is clearly not the case, at least in rats and humans. Nevertheless, in spite of severe acute rejection, it is interesting that cultured keratinocyte allografts are very poor at evoking antibody responses in graft recipients. Where permanent survival of the keratinocyte is required, autografts must be used, since the administration of immunosuppression to protect allografts would not be justified. Clinical application of cultured keratinocyte allografts, without immunosuppression, is limited to their use as temporary dressings (e.g., in burns) or to stimulate the recipient's own skin cells to growth (e.g., on leg ulcers). Autografts have been used for patients with extensive burns and in the treatment of chronic mastoiditis.