CD4 and neoplasm: To experimentally investigate how CD4+ T cell effector functions could be therapeutically directed against MHC-deficient tumours that evade CD8+ T cell immunity, we used enhanced green fluorescent protein (eGFP+) TRP-1 CD4+ TCRtg T cells and Venus+ Pmel-1 CD8+ TCRtg T cells for ACT immunotherapies21,22.