Using monoclonal antibodies the subpopulations of mononuclear cells were studied in peripheral blood in patients with multiple sclerosis in active phase of the disease. The results suggested the following

Conclusions: 1. In the active phase of multiple sclerosis (during exacerbations and slowly progressive course) a rise occurs in the proportions of Ia-positive and M1-positive cells without changes in the proportions of T4 and T8 lymphocytes and in their mutual ratio. 2. No differences were observed in the percent of peripheral blood mononuclear cells between all patients in the active phase of the disease and those with slowly progressing disease. 3. During immunomodulatory treatment (alternating administration of prednisone and levamisole) a rise was observed in the percent of suppressor cells T8/Ia-positive, and a fall in the T4/T8 suppressor cell ratio.