The median percentages of peripheral blood immunoglobulin-positive (Ig+) lymphocytes (8%, n = 46), CD8+ (12%, n = 49) and CD57+ cell numbers (5%, n = 37) of patients suffering from multiple sclerosis (MS) were significantly (p less than 0.05) lower than the values of age- and sex-matched healthy individuals (Ig+ cells: 13%, n = 46; CD8+ cells: 17%, n = 49; CD57+ cells: 9%, n = 37). Comparison of calculations on decreased peripheral blood cell counts and increased brain cell counts in MS patients revealed that sequestration of blood cells into the MS brain is a possible explanation of these findings.