PRF1 and neoplasm: Indeed experimental evidence suggests that central (TCM) and effector (TEM) memory T cells can each confer a protective advantage [17-19], with TCM providing a reservoir of antigen-specific T cells, ready to expand and replenish the periphery upon secondary challenge, and TEM displaying a more activated phenotype capable of granzyme B and perforin expression, IFN-γ secretion, and tumor-specific killing in vitro [17].