A novel pathway of CD8+ T-cell activation by a previously established human Langerhans cell (LC)-like cell line, ELD-1 [Dendritic Cells 9 (1999) 41] is reported. ELD-1 cells possess LC-specific and dendritic cell (DC) lineage-specific markers including Birbeck granules. Intriguingly, ELD-1 cells stimulated interferon (IFN)-gamma production by purified allogeneic CD8+ T cells in an IL-2- but not IL-12-dependent manner, but failed to stimulate CD4+ T cells due to their lack of HLA-DR, CD40, CD80, and CD86 expression. Comparing active and inactive subclones of ELD-1 cells revealed that CD70 was a key molecule determining stimulatory ability. This was confirmed by the ability of transfected CD70-encoding cDNA to confer stimulatory capacity on inactive subclones of ELD-1. Therefore, it is concluded that CD70 expressed on ELD-1 cells has a crucial role in stimulating IFN-gamma production by CD8+ T cells through an alternative pathway which does not require CD4+ T-cell help or CD28-B7 interactions.