CD44 and neoplasm: Similarly to influenza virus-specific cells during acute infection, we found that at day 15 tumor-specific (OVA(257−264) MHC-I Tetramer+ OT-I) effector CTL that had migrated into the tumor site displayed an activated phenotype including CD44 upregulation and simultaneous downregulation of CD62L, IL-7R (CD127) expression, and upregulation of CD69 (an early marker of T cell activation) (Supplementary Figures 1A–E).