Multiple sclerosis patients show an increased spontaneous activity of their peripheral blood monocytes as measured by chemiluminescence.

I has been reported that myelin basic protein (BP) reacts extremely sensitively to peroxide, which is formed when monocytes/macrophages are stimulated to produce a "respiratory burst" (RB). We measured the RB activity by means of chemiluminescence in peripheral blood monocytes/macrophages (MO) of 17 MS patients, 5 patients with a viral infection of the CNS, and 14 control persons. The median of the spontaneous RB activity of MS patients compared with the median of our control group showed a highly significant increase (P = 0.0002). All MS patients examined possessed a clearly increased MO activity. The highest values, however, were found in MS patients in a bout (means = 315%, means = 296%). Since a viral infection is discussed as being involved in the pathogenesis of MS, we also examined patients with a viral infection of the CNS, but this group of patients did not show a significant increase (P = 0.34). Our data indicate that MO in MS patients generate and/or secrete an increased amount of unspecific mediators of inflammation. The possibility is discussed that this altered MO function might be caused by an altered reaction of MO in MS patients to a viral infection or superinfection.