CD4 and neoplasm: Single-cell cytotoxicity assays of cytotoxic CD4+ T cells specific for tumor antigen (NY-ESO-1 and MAGE-A3), which were isolated using MHC class II tetramers, demonstrated their direct killing of tumor cells pre-treated with IFN-γ or stably transduced with CIITA to enhance MHC class II expression (Cachot et al., 2021).