Long-term survival and immunological tolerance of human epidermal allografts produced in culture.

Human epidermal cells from a small skin specimen can be grown in culture into multilayered sheets suitable for the permanent coverage of large burn wounds when used as epidermal autografts. We report here on the long-term survival of such cultured epidermal sheets used as epidermal allografts (EAG) across a major histocompatibility barrier in three nonimmunosuppressed adult patients, suffering from large chronic grafted leg ulcers, where the EAG have been placed to cover the conventional split-thickness skin autograft donor site. The absence of rejection was based upon clinical, histological, and immunopathological observation of the allografted sites at various intervals after grafting of the EAG. The identity of the epidermal cells on the grafted area with cultured cells from allogeneic donor was then established after blood substance typing by indirect immunofluorescence. Furthermore, epidermal cells from cultured sheets, but not control human cells from freshly excised normal epidermis, failed to stimulate the recipient peripheral blood cells in the mixed epidermal cell lymphocyte culture reaction, a finding that is related to the complete absence of class-II-antigen-bearing cells in cultured epidermis. This absence of T cell stimulation was noted not only on the day of grafting but throughout the follow-up. Altogether, these findings show that Langerhans cell and other class-II-antigen-bearing cell-depleted cultured epidermal allografts, are tolerated in unrelated recipients. EAG may serve as a skin substitute in patients with large wounds or burns. Since EAG may be grown continuously, the coverage of burns may not then be limited by the availability of the donor site, or by the time necessary to produce epidermal tissue in cultures.