Association between epidermal interleukin-10 secretion and the ability of cotransplanted skin from neonatal donors to prolong adult allograft survival.

Cotransplantation of skin from neonatal donors prolongs the survival of adult skin allografts on rabbit anti-mouse lymphocyte serum-treated and donor bone marrow cell-treated mice relative to controls (the cotransplant effect). In B6AF1 (H2a/b) recipients, cotransplants of skin from C3HeB/FeJ (C3H; H2k) neonates up to 6-7 days old prolonged the survival of adult C3H skin grafts. Skin from 9- to 10-day-old neonates was inactive. The magnitude of the cotransplant effect declined with increasing cotransplant age. Although few class II+ cells are present in skin from < 24-hr-old mice, the numbers of these cells increase rapidly after birth. On days 3-4, when the cotransplant effect is strong, their numbers in neonatal skin are greater than in adult skin. Development of class II expression continues when neonatal skin is grafted, but with an apparent 2-day lag. Because class II+ cell numbers decline in grafted adult skin, we speculate that this apparent developmental lag may be due to Langerhans cells migrating from the graft as they mature. Epidermal cells from litters of neonates were cultured overnight and supernatants were tested for interleukin (IL)-10. All 11 samples from 0- to 4-day-old neonates and 4 of 9 samples from 4- to 7-day-old neonates were positive. IL-10 was found in 1 of 9 samples from donors 8-16 days old and 1 of 7 samples from individual adult mice. Thus, there is a temporal association between the ability of neonatal skin to produce a cotransplant effect and its ability to secrete IL-10.