Figure 6.

Thiol-dependent proliferation of LP-T. (A) Cystine-deficient RPMI 1640/10% FCS was supplemented with graded amounts of cystine at the indicated final concentrations. Concentration of 2-ME was 10 μM. Irradiated PB-MOs were added at 30% of total cell number. (B) Stimulatory potential of cysteine versus equimolar amounts of cystine on the proliferation of LP-Ts after CD3 (OKT3) or CD2 (M1+M2) stimulation. LP-Ts were plated at 8 × 10⁵/well in an initial volume of 1 ml/well in 24-well plates. Cultures were primarily set up in cystine-deficient medium, and were supplemented with cysteine in 15-μl volumes every 6 h at a final concentration of 30 μM each time. Cysteine had to be added repeatedly because of rapid oxidation to cystine under culture conditions. Alternatively, cultures received equimolar amounts of cystine. After 84 h of culture, wells were pulsed with [³H]-TdR at 5 μCi/ml, and cells were harvested 18 h later.