In melanoma and NSCLC, response rates to anti-PD-1 treatment correlate with the presence of existing tumour infiltrating lymphocytes (TILs) and proliferation of cytotoxic CD8+ T cells at the tumour margin and intratumourally (Tumeh et al., 2014) (Maibach et al., 2020). The gene discussed is CD8A; the disease is neoplasm.