Indeed, previous studies have employed activation, exhaustion, or tissue-resident markers such as 4-1BB (Ye et al., 2014), PD-1 (Inozume et al., 2010; Gros et al., 2014; Zheng et al., 2022), CD39 (Zheng et al., 2022; Simoni et al., 2018), and CD103 (Webb et al., 2010; Duhen et al., 2018), or the specificity of a TCR for a melanoma-associated or melanoma-specific antigen (Yee et al., 2002; Dudley et al., 2002). The gene discussed is PDCD1; the disease is melanoma.