DTT, but not reduced glutathione, primes MOLT-4 cells for Gal-1–induced apoptosis. (A) MOLT-4 cells were treated with 3 mM DTT or 3 mM reduced glutathione (RG) as indicated with or without 10 μM Gal-1 for 9 hours followed by detection for PS exposure (annexin-V⁺/PI⁻) and membrane integrity loss (annexin-V⁺/PI⁺). Error bars represent the standard deviation of duplicate samples. MOLT-4 cells were treated with PBS (B), 3 mM DTT (C), 3 mM RG (D), 10 μM Gal-1 (E), 10 μM Gal-1 + 3 mM DTT (F), or 10 μM Gal-1 + 3 mM RG (G) for 9 hours followed by detection for changes in the light-scattering properties of the cell. Gate values of cells experiencing no changes in forward- and side-scatter profile are shown.