Kinetics of human DC-mediated cross-presentation of antigens derived from apoptotic or necrotic cells infected with Vac-MP. Vaccinia-infected apoptotic or necrotic HLA-mismatched monocytes were cocultured with IDCs at a ratio of 0.6 (A-B) or 2 (C-D) per DC, with or without maturation stimuli. The monocytes had previously been infected with Vac-ctr or Vac-MP for 12 hours, prior to undergoing apoptosis or necrosis. DCs were harvested at different time points between 0 and 48 hours, washed, and fixed in glutaraldehyde. The ability of immature (A,C) or mature (B,D) DCs to cross-present MP was assessed with the clone Flu16 in an IFN-γ ELISPOT assay. Controls consisted of dead cells and Flu16 alone or together, which did not yield IFN-γ production (unpublished data). Panels A-D show 1 representative experiment of 4, respectively.