Recombinant Jurkat cell line expressing firefly luciferase under the control of an IL-2-responsive promoter, and with constitutive expression of human KIR3DL3 (Killer Cell Immunoglobulin Like Receptor, Three Ig Domains and Long Cytoplasmic Tail 3; GenBank accession #BC143802.1 corresponding to KIR3DL3*00402 allele). HHLA2 (B7-H7) mediates an immune-stimulatory signal via TMIGD2 (Transmembrane and immunoglobulin domain containing 2; CD28H) in na?ˉve T cells while it delivers an immune-inhibitory signal through KIR3DL3 in activated T cells and Natural Killer (NK) cells.