Although it is well established that epidermal Langerhans cells (LC) originate from bone marrow, little is known about the mechanism of this migration into the epidermis from bone marrow. In order to clarify the mechanism of this migration, we constructed an in vitro model. LC were depleted by daily topical application of clobetazole propionate (CP) solution onto the ear of Balb/c mice. Seven days later, ear skin was cut off, separated and co-cultured dermal-side-up with syngeneic (Balb/c), semisyngeneic ((C3H x Balb/c)F1), or allogeneic (C3H) epidermal cells (EC) for 3 days. We found (1) that a marked migration of donor LC into the recipient epidermis was observed in the LC-depleted skin, (2) that only syngeneic LC actively migrated into the recipient epidermis; however, the migration of semisyngeneic and allogeneic LC was detected at very low levels, (3) that the migratory capacity of donor LC was directly proved by a biolabeling technique using donor EC labeled with PKH-26, and (4) that anti-IL-6 and anti-TNF-alpha antibodies inhibited the migration of donor LC into the recipient epidermis. These data demonstrate that the resident LC have the potential to traffic through the dermis into the epidermis in a highly syngeneic-specific fashion, and that IL-6 and TNF-alpha are partially responsible for promoting this migration.