Interferon gamma producing blood lymphocytes are decreased by interferon beta therapy in patients with multiple sclerosis

Objective: We studied the individual course of interferon gamma producing blood lymphocyte count (IFGC) of 15 multiple sclerosis patients started on 8 MIU beta interferon administered subcutaneously each other day Methods: Mononuclear blood cells were prepared before treatment and on day 3, 9, 15, as well as after month 1, 2, 3 and 4 of therapy. After stimulation intracellular interferon gamma was detected with monoclonal fluorescent antibodies and measured by flowcytometry. IFGC is given as percentage of oil gated lymphocytes. Results: forty-eight hours after first interferon beta application the mean IFGC dropped significantly from 11.37 to 7.09 (P < 0.05) and to 4.22 within 4 months. Whereas the majority of patients showed a decrease of IFGC from the beginning of therapy in three of the 15 patients a transient increase of IFGC was seen suggesting a different response to immunomodulatory therapy. Conclusions: Interferon gamma producing lymphocyte count might be a useful tool to determine the biological effect of interferon beta therapy in multiple sclerosis patients.