Immunotherapies targeting CD4+ T cell responses are showing promise, with clinical activity of cancer vaccines and of adoptive T cell therapies for melanoma and other cancers.3 4 48 Our prior work has demonstrated that vaccines using 6MHP emulsified in IFA have clinical activity10 and can induce CD4+ T cell responses in most participants, while also supporting induction of peptide-specific Ab responses.6 However, some T cell responses with IFA are transient, and not all participants develop strong responses. This evidence concerns the gene CD4 and cancer.