TALL-104/GFP cells are derived from the human leukemic T cell line TALL-104 by stably integration of a constitutive GFP stably expression construct. The TALL-104 cells are CD8+ cytotoxic T lymphocytes (CTLs), are involved in immune signaling, especially in the context of T cell receptor (TCR) signaling. The TALL-104 cells are widely used in the development and testing of immunotherapies and anti-cancer drug screening. TALL-104/GFP cells stably stably express GFP, can be used for in vitro assays and in vivo imaging.