CD4 and neoplasm: Cytotoxic CD4+ T cells also express GNLY, which has a documented role in anti-microbial immunity (reviewed in Krensky and Clayberger, 2009); although a proven role in anti-tumor responses has not been documented, profiling of single-cell clones with cytotoxic activity pointed to an enrichment of GNLY expression in this population (Cachot et al., 2021).