Reduction of serum IL-10 in As₂O₃-treated MRL/lpr mice. Serum IL-10 levels were quantified by ELISA in the sera of (A) untreated 4-month-old MRL^+/+ and MRL/lpr (B) 2-month-old MRL/lpr mice that had been treated daily for 2 months with 2.5, 5, 7.5, or 10 μg/g As₂O₃ or PBS. Black squares represent data from individual animals and bars correspond to the mean for 3 to 4 mice per group.