CTLA4 and cancer: The fact that patients with some cancer histologies/molecular profiles respond to immune checkpoint inhibitors (ICI), such as anti-PD-1, anti-CTLA-4, and anti-PD-L1 allows the study their impact on non-target T-cell populations (those not directed specifically against cancer-associated mutations or neoantigens), i.e., on CMV or EBV-reactive T cells.