CD80 and cancer: T cell activation requires two stimulatory signals – the T cell receptor (TCR) signal formed by the combination of TCR and the antigenic peptide–MHC complex, which is in itself not enough to activate T cells, and the costimulatory signal provided by the combination of CD28 and CD80, required to fully activate T cells.[102, 103] To achieve better anticancer efficacy by fully activating T cells, Zhang and co‐workers engineered cancer cells to express CD80 costimulatory signals, generating a B16–CD80 cell line.