Extremely high serum level of IgE during immunosuppressive therapy: paradoxical effect of cyclosporine A and tacrolimus.

A case of X-linked autoimmune enteropathy was successfully treated with cyclosporine A (CsA) or tacrolimus (FK506) and developed extremely high serum levels of IgE during the immunosuppressive therapy. Serum IgE levels increased from 190 to 1,000-2,500 IU/ml with CsA therapy and as high as 80,000 IU/ml with subsequent FK506 therapy. Serum IgG2 and IgG4 levels were slightly elevated compared to serum IgE levels. Thereafter, serum IgE levels progressively decreased in parallel with a reduced dosage of FK506. Total serum IgG levels and peripheral eosinophil counts, however, showed no significant changes during the course. These observations suggest that both CsA and FK506, potent immunosuppressants, could paradoxically enhance some immune responses, possibly through the action of CsA-/FK506-resistant immune systems.