As an initial attempt to gain a better understanding of the basis for the increased incidence of ultraviolet-light-related skin cancer in chronically immunosuppressed human renal allograft recipients, we have compared both morphological and functional characteristics of epidermal Langerhans cell (LC)5 populations present in the forearm skin of nine such patients with those of age, sex, and race-matched controls. The LC surface densities in vacuum-induced blister-derived epidermal sheets taken simultaneously from extensor and flexor forearm skin of the patients were significantly lower than those observed in the controls. The most abnormal LC densities seen were in the patients’ extensor forearm skin. Likewise there were disturbances in LC distribution and morphology that were most marked in the extensor forearm skin of patients. Differences in the alloantigen-presenting capacity of LCs present in epidermal cell suspensions prepared from patient and control forearm skin were also noted—however, these differences were not as great as were the LC density differences. The alloantigen-presenting capacity of patients’ LCs was depressed proportionately more than was the alloantigen presenting capacity of their peripheral blood mononuclear cells. These results demonstrate that the LC population is clearly perturbed in human renal allograft recipients and that this perturbation is greatest in a sun exposed region of skin.
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