CFP and neoplasm: To understand the migratory behavior of endogenous TILs in the rechallenged tumors, we used intravital microscopy to observe the dynamic behavior of TILs (GFP+) in the tumor areas 11 days after tumor rechallenge (51 days after the treatment of primary tumors), with 2×105 CFP-B16 tumor cells implanted into a skin-fold window chamber on the back of Cxcr6+/gfp transgenic (CXCR6-GFP) mice.