Thymocytes from 10-week-old rag2-EGFP-bcl-2 transgenic fish are resistant to irradiation-induced apoptosis. Fluorescent microscopic analysis of rag2-GFP transgenic fish without γ-irradiation (A) or 1 day or 4 days after irradiation treatment (20 Gy; B and C, respectively). rag2-EGFP-bcl-2 transgenic fish without γ-irradiation (D) or 1 or 4 days after irradiation treatment (E and F, respectively). Location of the thymus is denoted by arrows and labeled (T). Fish oriented with anterior to the left and dorsal to the top.