Fig. 4. Sub-cellular localization of mature IL-1. (A) Wide-field fluorescence images of LPS-treated (1 µg/ml, 2 hours) murine macrophages in the absence or presence of ATP (5 mM, 5 minutes). Cells were immunostained for IL-1 (green) and cathepsin D (CD, red), before (non-permeabilized), and after digitonin treatment. Bar, 10 µm. (B) Immunoblot for IL-1 in supernatants isolated from the experiment described in A. C, control; T, supernatants isolated from macrophages permeabilized with Triton X-100. Images and blots are representative of three independent experiments.