In a prophylactic vaccination setting a TE/TEM phenotype is thought to be less effective compared to a predominant central memory CD8+ T cell (TCM) phenotype due to their limited proliferation potential [43], however in a therapeutic setting with the continued persistence of OVA antigen in the tumor it is not unexpected that they express an activated effector phenotype and others have shown this to correlate with a higher level of PD-1 expression [44]. This evidence concerns the gene PDCD1 and neoplasm.