Figure 1.

Fas expression and apoptosis of PELA. (a) FACS analysis of Fas expression in PELs, detected by Fas antibody staining. PELs [syngeneic (B/6 anti-EL4) and allogeneic (B/6 anti-L1210)] were compared with Fas positive (LF⁺) and negative (LF⁻) controls. Cells (0·25 × 10⁶) were washed in staining medium (0·5–1% BSA in PBS + 0·02% azide), pelleted, suspended in 30 µl (0·25 µg) of hamster anti-mouse CD95 antibody (Jo2), and incubated on ice for 30 min with occasional shaking. After the cells were washed and pelleted, they were suspended in 30 µl of FITC-goat anti-hamster F(ab)₂ antibody (1:100 dilution) and incubated and washed as above. (b) Flow cytometric analysis of PEL apoptosis by propidium iodide (PI) staining. PEL (AKR anti-L1210) were compared with LF⁺ cells. Upon treatment of LF⁺ cells (but not PEL) with Jo2, a new peak in the cell cycle appeared, defined as A₀ or sub-G₀ (M1-marked area), which represents apoptotic cells. No sub-G₀ was found in PEL. The percentage of cells in apoptosis is indicated in parenthesis. No sub-G₀ peak was found with LF⁻ cells (not shown).