The thymus is expanded in rag2-EGFP-bcl-2 transgenic fish. Fluorescent microscopic analysis of 52-day-old rag2-EGFP-bcl-2 transgenic fish having enlarged thymi (B) when compared with age- and sex-matched rag2-GFP fish (A). Bar denotes length of the ventral-most portion of the thymus in rag2-EGFP-bcl-2 fish. Fish oriented with anterior to the left and dorsal to the top.