Wild-type or Bid-deficient cells (2610 5 ) were grown in 24-well plates and adsorbed with reovirus at room temperature for 1 h. Following removal of the inoculum, cells were washed with PBS and incubated in complete medium at 37uC for 18 h. Monolayers were fixed with methanol, washed twice with PBS, blocked with 2.5% Ig-free bovine serum albumin (Sigma-Aldrich) in PBS, and incubated successively for 1 h with polyclonal rabbit anti-reovirus serum at a 1:1000 dilution and for 1 h with Alexa Fluor 546labeled anti-rabbit IgG at a 1:1000 dilution. Monolayers were washed with PBS, and infected cells were visualized by indirect immunofluorescence using a Zeiss Axiovert 200 fluorescence microscope. Reovirus antigen-positive cells were quantified by counting fluorescent cells in at least two random fields of view in triplicate wells at a magnification of 206.