Migration of Thy-1⁺ dendritic epidermal cells (Thy-1⁺DEC): Ly48 and TNF-α are responsible for the migration of Thy-1⁺DEC to the epidermis

Thy-1⁺ dendritic epidermal cells (Thy-1⁺DEC) are mainly T cells that express T-cell receptor γ and δ chains with limited diversity of γδ, mainly γ3δ1; such γ3δ1 TCR-bearing Thy-1⁺DEC originate from day 16 fetal thymic cells. To understand the migratory capability of Thy-1⁺DEC, we developed an in vitro model, using skin organ culture. First, emigration of Thy1⁺DEC from the epidermis was examined. Ear skin from C3H/He mice was separated into two parts and incubated for 3 d with dermal side down. Thy-1⁺DEC emigrated from the epidermis into the dermis and then migrated out of the skin into the culture medium. Next, immigration of Thy-1⁺DEC into the epidermis was examined. Thy-1⁺DEC were depleted in vivo by daily application of clobetazole propionate solution topically onto the ears of C3H/He mice. Seven days later, ear skin was harvested, separated, and cultured with the dermal side up with syngeneic epidermal cell suspensions with a migration chamber for 3 d. It was found that 1) Thy-1⁺DEC immigrated into the Thy-1⁺DEC depleted epidermis as well as into untreated epidermis, and 2) the migratory capability of Thy-1⁺DEC was directly proved by a biolabeling technique with PKH-26. Blocking studies with various antibodies revealed that leukosialin (S11 monoclonal antibodies) and TNFα were important for Thy-1⁺DEC migration. Thus, Thy-1⁺DEC retain the potential for migration in vitro, and leukosialin and TNFα are partially responsible for the migration of Thy-1⁺DEC into the epidermis.