Killing of skin-derived tumor cells by mouse dendritic epidermal T-cells

Dendritic epidermal T-cells (DETC) are a unique population of T-cells that reside normally in mouse epidermis and express a gamma delta T-cell receptor. We have reported previously that DETC acquire in culture the capacity to lyse the YAC-1 lymphoma, a conventional target for natural killer cells. The aim of the present study was to characterize this cytotoxic potential, using a spectrum of skin-derived mouse tumors. Cytotoxicity was measured by a 51Cr release assay and by the visual assessment of target cell lysis. Long-term DETC lines, established from CBA, AKR, and BALB/c mice by mitogenic stimulation and repeated feeding with interleukin 2 (5 units/ml), were used as effectors. Skin-derived tumor targets included 5 melanoma lines and the transformed keratinocyte line Pam 212. Each DETC line lysed skin-derived tumors as well as YAC-1 targets effectively in the 18-h 51Cr release assay, and target lysis occurred in a non-major histocompatibility complex-restricted manner. By contrast, freshly isolated spleen cells lysed YAC-1 but not skin tumor targets. Moreover, confluent monolayers of melanoma or Pam 212 targets were disrupted completely by added DETC lines but not by spleen cells. The cytolytic activity of DETC appeared to be specific for tumor cells, since normal mouse keratinocyte monolayers remained intact under the same conditions. Finally, DETC freshly isolated from skin failed to exhibit significant cytotoxicity but acquired this capacity 10-14 days after mitogenic stimulation and feeding with interleukin 2 (5 units/ml). We conclude that DETC possess the potential to recognize, bind, and lyse tumor cells that originate in skin.