Determination of interferon-gamma in the peripheral blood of multiple sclerosis patients in remission, using a chemiluminescence technique.

The plasma from eight patients with multiple sclerosis (MS) whose disease was in remission, was investigated by a chemiluminescence technique for its ability to stimulate the oxidative metabolism of peripheral blood monocytes (PBM). The active fraction identified had a molecular weight between 13,700 and 43,000 Da. Its activity was reduced by incubation at pH 2, pH 4 or pH 6, or by treatment at 56 degrees C for 1-3 h. The activity was also decreased, 58-100%, by prior incubation with antibodies to human interferon-gamma (IFN-gamma). We suggest that these results indicate that the increased chemiluminescence activity (CL-A) of PBM in MS patients in remission is due mainly to the presence of circulating IFN-gamma.