Immunological tolerance of sheep to skin allografts.

A majority of grafts of adult sheep skin placed on fetal lambs at 55 days gestation were retained and increased 50-100-fold in area by the time of birth. Although the original grafts placed in utero survived, second and third grafts from the same donors were rejected. Lambs bearing skin grafts attained full mixed leukocyte reactivity against cells from the skin donors.