As the T2 cell line and cultured human melanoma cell lines do not express spontaneously PD-L1, we previously established these PD-L1 expressing cell lines through stable transfection of a PD-L1 expression plasmid.36 The reactivity of T cell clones was tested on the PD-L1-positive cell lines and their non-transfected counterparts by IFN-γ and IL-2 specific ELISA tests after a 12 hours activation period (figure 5A, B). Here, CD274 is linked to melanoma.