Serum viral antibody titers against 21 viruses were studied in 19 of 23 same-sex twin pairs with
multiple sclerosis derived from the Finnish Twin Cohort. Thorough neurologic examinations showed two monozygotic pairs to be concordant, whereas all dizygotic pairs were discordant. Special attention was given to
measles,
mumps, and
rubella viruses, against which the antibody levels were determined with the
complement fixation, hemagglutination inhibition,
hemolysis-ingel, and
enzyme immunoassay methods. Epstein-Barr virus antibody levels were determined by
enzyme assay. In pairwise comparisons, the
measles,
mumps, and Epstein-Barr virus-
IgG antibody levels were more often elevated in the patients with
multiple sclerosis, compared with the healthy co-twins. The same antibody levels were more often above the median in the diseased twin, compared with the healthy twin, but the difference was not significant. No human T-cell lymphotropic virus type I
antibodies were found in any of the individuals examined. The total
IgG,
IgA, and
IgM levels did not differ between the diseased and healthy subjects. The HLA types, severity of the disease, and cell-mediated immunity parameters did not influence antibody levels.