Thin-section electron micrographs of BCBL-1 cells induced with TPA (20 ng/ml) for 48 h in the absence (A and B) or presence (C and D) of anti-IFN-α Ab (100 IU/ml). Cells in various stages of particle maturation and cytopathic effects are shown. (A) Cell induced with TPA in the absence of anti-IFN-α Ab, showing intranuclear aggregation of virus-specific electron-opaque material (arrows). (B) Cell induced with TPA in the absence of anti-IFN-α Ab, showing HHV-8 particles in different stages of maturation (nucleocapsids [arrowheads] and complete virions [arrows]). (C) Cell induced with TPA in the presence of anti-IFN-α Ab, revealing capsids in various stages of packaging of viral DNA (arrowheads) and numerous complete virions at the cell surface. (D) Extensively lysed cell induced with TPA in the presence of anti-IFN-α Ab, in which nucleocapsids with typical hexagonal outlines and variable DNA cores in the nucleus and in the cytoplasm can still be observed. Bars, 1 μm.