Proliferation profile of TIL isolated from rat osteosarcoma. These data are representative of three independent tumors. TIL isolated from rat osteosarcoma biopsies by enzymatic treatment were cultured at 5 × 105 TIL per well (6-multiwell plate) for 28 days in X-VIVO 15 supplemented with 900 UI/ml IL-2. At day 23 (arrow), 20 × 103 irradiated (75 grays) autologous osteosarcoma cells were added in each well. TIL were manually numbered using the trypan blue staining.