Cancer-specific mutations have been demonstrated to be viable targets for tumor-infiltrating lymphocytes (TILs) enabled by checkpoint inhibitors that block CTLA4 or PD1/PDL1 or by vaccine-induced immune responses (van Rooij et al., 2013; Carreno et al., 2015; Cohen et al., 2015; Gros et al., 2016; McGranahan et al., 2016; Ott et al., 2017; Zacharakis et al., 2018; Hilf et al., 2019). The gene discussed is CTLA4; the disease is cancer.