Inhibition of acid β-glucosidase activity by sera from cases 1 (×) and 2 (•). Controls sera were from normal individuals (+), and antibody positive (▪) and antibody negative (▴) Gaucher disease patients. Acid β-glucosidase, as alglucerase, was incubated with varying amounts of serum at pH 5.5 in the absence of detergents. The decrease in enzyme activity at greater than 15 μL of nonimmune serum are due to denaturation.