Fig. 7. Hck lysosomes fuse with phagosomes containing M. kansasii only when mycobacteria are serum-opsonized. MDMs were infected with non-opsonized or immune-serum-opsonized FITC-M. kansasii under synchronized conditions. Two hours post-infection, cells were fixed and immunolabeled for CD63 or Hck. Secondary Abs were TRITC-conjugated. We focused on phagosomes. Phagosomes containing non-opsonized or serum-opsonized mycobacteria (A,C) were positive for CD63 (B,D) (arrows). Some non-opsonized mycobacteria (A) were also found in CD63-negative phagosomes (B) (arrowheads). Phagosomes containing non-opsonized mycobacteria (E) were negative for Hck (F) (arrows) although phagosomes harboring serum-opsonized mycobateria (G) were positive for Hck (H) (arrows). Data are from one experiment that is representative of three independent experiments. Bar, 5.5 µm.