FasL levels return to normal in As₂O₃-treated MRL/lpr mice. Level of cell-surface–anchored form of FasL from 4-month-old MRL⁺/+ (white bars) and MRL/lpr (gray bars) mice that had been treated daily with PBS (–) or As₂O₃ (5 μg/g) (+) for 2 months were analyzed by Western blotting of lymphoid-cell lysates from 8 individual mice using anti-FasL mAb. The blot was stripped and reprobed with antiactin mAb. (B) ELISAs were used to determine their serum FasL concentrations. Black squares represent data from individual animals and bars correspond to the mean for 6 to 12 mice per group.