It is noteworthy that a substantial proportion of adult CD8 T cells lack the CD28 co‐stimulatory molecule, and the gradual expansion of this T cell subset is a hallmark of immune system aging.[56, 57] The loss of CD28, a critical costimulatory molecule, is associated with tumor cell resistance to immunotherapeutic interventions[58] Additionally, heterogeneous populations of CD8+CD28− senescent T cells have been identified in various solid and hematogenous tumors. The gene discussed is CD8A; the disease is neoplasm.