Double-staining of cortical keratin 8 (red) and medullary keratin 5 (green) in the thymus of WT and Foxn1Tg mice (line 60). Acetone-fixed frozen sections of thymi from 2-month-old (A) and 26-month-old (B-C) WT mice and 2-month-old (D) and 31-month-old (E-F) Tg mice were stained with a rabbit-anti–mouse keratin 5 (green) and rat-anti–mouse keratin 8 (red). Sections were analyzed with a Zeiss LSM 510 confocal microscope. Images were obtained with CApo 40×/1.2 W with a 2 × 2 matrix and digitally stitched using the LSM 510 software. Scale bar represents 200 μm.