Ultrastructural appearance of SIV particles in DCs after 24 hours. Mature and immature DCs were pulsed with AT-2 SIV CP-mac for 2 hours, washed, and cultured for an additional 24 hours (immature DCs in GM-CSF and IL-4 and mature DCs in regular medium). At the 24-hour time point, cells were fixed and processed for electron microscopy as previously described.22 In mature DCs (A-C) large vacuoles (large white arrowheads) containing intact particles (black arrowheads) and cellular debris or possible degraded virions (asterisks) were observed. Similar virions (as well as debris or degraded viral particles) were observed in immature DCs (D-F), although at a markedly lower frequency. Magnifications and scale bars: (A) × 9000, 2 μm; (B) × 31 000, 100 nm; (C) × 81 000, 10 nm; (D) × 23 000, 0.5 μm; (E) × 60 000, 100 nm; (F) × 51 000, 100 nm. These images represent observations from 2 donors for the immature DCs and 4 donors for the mature DCs.
