Low T8 antigen density on lymphocytes in active multiple sclerosis.

The median fluorescence intensity of peripheral blood T8+ (T-suppressor/cytotoxic) cells in patients with active (relapsing or progressive) or stable multiple sclerosis (MS) and in control subjects was determined with a fluorescence-activated cell sorter using an indirect immunofluorescence assay. Median fluorescence intensity was significantly lower in patients with active MS than in controls. No differences in median fluorescence intensity were found between patients with stable MS and controls. Analysis of T8+ cells that had been modulated in vitro with OKT8 indicated that the resultant reduction in the median T8 antigen density per cell resulted in fewer T8+ cells being enumerated when the fluorescence-activated cell sorter was used than when a fluorescence microscope was used. Reduced median T8 antigen density on cells as found in active MS may contribute to the apparent underrepresentation of circulating T-suppressor cells in such patients and may be associated with reduced suppressor cell function.