Measurement of intracellular cytokines in MS patients treated with β-interferon and association of a β-interferon induced exacerbation with increased expression of γ-interferon by monocytes

The effects that immunomodulatory agents such as β-Interferon (IFN-β) exert upon cytokine production in autoimmune disease such as multiple sclerosis remain incompletely understood. The recent development of techniques to directly assess cytokine production within peripheral blood leucocytes promises to advance this field. β-Interferon treatment occasionally causes short-lived exacerbations of neurological dysfunction, often associated with systemic flu-like symptoms. Whereas these side effects usually occur and remit within the first few months of therapy, we have identifi ed several patients who have developed symptoms many months after the onset of treatment. To begin to investigate the cause of these late onset exacerbations, we assessed the intracellular cytokine profiles of two patients, one stable on IFN-β treatment and another experiencing side effects. The latter patient exhibited an increase in the percentage of monocytes that expressed g-Interferon after IFN-β administration, whereas no such modulation was seen in the patient without side effects.