Effect of therapeutic interventions on plasma CCL18 levels. (A) Plasma CCL18 levels in 2 individuals responding well to enzyme replacement therapy. (B) Plasma CCL18 levels in 2 individuals responding clinically poorly to enzyme replacement therapy. (C) Plasma CCL18 levels in 2 individuals on substrate deprivation therapy. (D) Plasma CCL18 levels in 2 untreated Gaucher patients. Closed symbols represent chitotriosidase wild-type individuals; open symbols, chitotriosidase-deficient individuals. The arrow indicates the initiation of therapy.