Peripheral blood lymphocyte sub-populations and multiple sclerosis.

Serial studies of lymphocyte sub-populations in patients with multiple sclerosis (MS) show periodic reductions in OKT8 cells (%). This alteration is neither immunologically nor disease-specific and also occurs in some apparently healthy normal individuals. In twice-monthly serial studies of lymphocyte sub-populations carried out over a 6-month period, we have found significant reductions in OKT8 cells on at least 2 occasions in 9/9 patients, 7/7 spouses and 3/11 siblings, but rarely in unrelated controls living in the same city. Abnormalities in these unaffected people occurred at the same time as those seen in their affected relative. Cyclical reduction in OKT8 cells is probably one factor associated with susceptibility to MS, perhaps only abnormal in terms of the frequency and duration with which it occurs, and may be related to environmental conditions affecting patients with MS and their close contacts but not most other unaffected individuals.