CD4 and cancer: The core module of cytolytic effector molecules appears largely conserved across murine and human viral, human aging, and human cancer contexts: notably, GZMB+ cytotoxic CD4+ T cells co-express GZMA and often GZMH, PRF1, FGFBP2, and granule-associated proteins NKG7 and (in humans) GNLY (Donnarumma et al., 2016; Patil et al., 2018; Hashimoto et al., 2019; Zhang et al., 2018, 2019; Oh et al., 2020; Cachot et al., 2021).