In vitro cytotoxic activity of interleukin 2-dependent murine Thy-1⁺ dendritic epidermal cell lines

Thy-1⁺ dendritic epidermal cells (Tdec) are bone marrow-derived cells of T-cell lineage. In order to investigate the function of these cells, two interleukin 2-dependent Tdec lines (AU4 and AU16) were established from ear skin of C3H/HeN (MTV^-) mice and examined for cytotoxicity against various murine tumor cells. The original phenotype of the Tdec, Thy-1⁺, AsGM1⁺, T3⁺, Lyt-1^-, Lyt-2^-, Lyt-5⁺, and L3T4^-, was maintained in the cell lines. The Tdec cell lines (AU4 and AU16) lysed a wide spectrum of tumor cell lines in a 4-hr ⁵¹Cr-release assay. AU16 was more effective in killing a syngeneic UV-induced skin tumor (UV-2240) and an allogenic, natural killer cell-resistant tumor (EL-4) than the YAC-1 cell line, which is highly sensitive to natural killer cells. Neither syngeneic nor allogeneic lymphoblasts were killed by AU16. Cytotoxicity was blocked by fixation of AU16 with paraformaldehyde but not by pretreatment of the cells with puromycin or mitomycin C. The finding that two Thy-1⁺ cell lines derived independently from murine epidermis have unique cytotoxic activity against murine tumor cells suggests that Tdec could play a role in local immune surveillance against skin cancers.