Cell death induced by CD86 blockade is only partially caspase dependent and has similarities to death induced by loss of IRF4. (A) Panels showing cell death represented as percentage of pLKO.1-infected controls over time in RPMI8226 cells overexpressing the indicated Bcl-2 family members (left). Representative histograms showing surface expression of CD28 or CD86 in 8226-pCDNA3.1 controls and 8226–Mcl-1 transfectants (right). (B) Cell death levels measured via percentage of annexin V⁺ cells at day 4 postinfection. For Q-VD-Oph–treated cells, the caspase inhibitor was added at day 2 postinfection. All data are from day 4 postinfection. (C) Representative western blots showing caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage with silencing of CD28 or CD86, with or without Q-VD-Oph. (D) Cell death with IRF4 or CD86 silencing was measured via annexin V staining, in the presence or absence of Q-VD-Oph. (E) Representative western blots showing expression of IRF4, caspase 3, and PARP when CD86 or IRF4 are silenced in MM.1s and 8226 cells. Data shown are mean ± SEM or representative of at least 3 independent experiments. *P < .05. UNT, untreated.