PRF1 and neoplasm: The T-box transcription factors (T-bet) and eomesodermin (Eomes) cooperate to promote cytotoxic lymphocyte formation, which correlates with the upregulation of perforin and granzyme B in antigen-specific cells,26 38 39 as well as sustaining memory phenotypes.40 Thus expression of T-bet and Eomes was examined in T cells within the spleen, tdLN and tumor of anti-hOX40-treated mice to better understand the mechanisms involved.