Effect of Radioactive Iodine Therapy on Cytokine Production in Graves’ Disease: Transient Increases in Interleukin-4 (IL-4), IL-6, IL-10, and Tumor Necrosis Factor-α, with Longer Term Increases in Interferon-γ Production1

Spontaneous and mitogen-stimulated production of interleukin-4 (IL-4), IL-6, IL-10, IL-12, interferon-γ (IFNγ), and tumor necrosis factor-α were evaluated by enzyme-linked immunospot assay of peripheral blood mononuclear cells from patients with Graves’ disease immediately before and at 4, 17, and 59 days after treatment with radioactive iodine. Patients had significantly reduced IL-4 and IFNγ production before treatment compared with healthy controls. Both cytokines were increased to normal levels by day 17 after treatment, and IFNγ remained at normal levels on day 59, whereas IL-4 returned to subnormal levels at this time. IL-12 production was initially normal and was not significantly altered by therapy. IL-6, IL-10, and tumor necrosis factor-α were also normal before radiotherapy, but increased significantly on day 17, returning to pretreatment levels by day 59. Thus, radioiodine treatment induced a transient increase in both proinflammatory and antiinflammatory cytokines and a more prolonged increase in IFNγ production, the latter representing a definite shift toward a type 1 cytokine profile.