The detection of circulating neoantigen-specific CD8+ T cells in cancer patients has been historically challenging due to many factors, including the rarity of these cells in the circulation (they are likely enriched within tumors but may or may not recirculate), and the limitations of neoepitope candidate prediction algorithms, which may result in identification of epitopes that are not presented by the tumor cells and not immunogenic [20, 21]. The gene discussed is CD8A; the disease is cancer.