Ferritin colocalizes with the late endolysosomal marker cathepsin D, but not with Golgi or early endosomal markers. (A-C) Representative confocal images of ferritin (red) and subcellular compartments (green) in the Golgi apparatus (A), stained for GM-130; early endosomes (B), stained for EEA1, and late endolysosomes (C), stained for cathepsin D (CatD), in murine BMDMs grown in the presence of 100 µg/mL FAC for 24 hours. Scale bars represent 10 µm. (D) Enlargement of ferritin-CatD co-staining, with red arrows indicating ferritin, green arrows indicating late endolysosomes, and yellow arrows indicating colocalization. Negative controls were treated with secondary antibodies only and with 1 primary antibody followed by both secondary antibodies (not depicted). Sample visualization was performed with a LSM 700 (Zeiss) laser scanning inverted confocal microscope equipped with a Plan-Apochromat ×63/1.4 numerical aperture oil differential interference contrast objective.