Fatigue is a common side effect of interferon (IFN) therapy, reported in 70–100% of patients treated with IFN. The etiology of IFN‐mediated fatigue (IMF) is multifactorial, with endocrine failure, neuropsychiatric disturbance, autoimmunity, and cytokine dysregulation potentially being contributors. Thyroid dysfunction, associated with the development of autoantibodies, is seen in 8–20% of patients receiving IFN‐α. IFN‐α also suppresses the hypothalamic‐pituitary‐adrenal axis. In addition, IFN‐α therapy leads to depression and cognitive slowing, and depressed patients are predisposed to develop fatigue. Clinical management of IMF is challenging because the syndrome is variable in onset and severity and the pathophysiology is poorly understood. Current management typically centers on dose reduction, but ancillary nonpharmacologic measures may help improve symptoms. Other strategies include antidepressant or anxiolytic therapy and treatment of coexisting hypothyroidism. Future studies utilizing IFN should include quantitative guidelines for grading and managing IMF. Cancer 2001;92:1664–68. © 2001 American Cancer Society.

In this study, we preincubated the sera of 3 patients with neuropathies associated with elevated titers of IgM anti-GM1 antibodies, with increasing concentrations of intravenous Ig (IVIg) and assayed the inhibitory effect of this mixture on antibody binding to immobilized GM1 by an enzyme-linked immunosorbent assay. Pharmacologic concentrations of IVIg, ranging from 0.1 microgram/ml to 100 mg/ml, inhibited anti-GM1 binding to its target antigen from 26 +/- 3 to 71 +/- 7%, respectively, in a dose-dependent manner. A similar inhibition of binding was also observed with IVIg F(ab')2 fragments. These findings provide a possible mechanism for the clinical efficacy of IVIg in motor neuropathies.

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