CD4+CD25+FoxP3+ T lymphocytes fail to suppress myelin basic protein-induced proliferation in patients with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disorder directed against self antigens of the central nervous system. CD4⁺CD25⁺FoxP3⁺ regulatory T cell (T_reg) mediated suppression is an essential mechanism of self-tolerance. We studied whether changes in the suppressive function of a mixture of CD25^high and CD25^intemediate expressing T_reg cells in myelin basic protein (MBP)-induced proliferation occurred in untreated MS patients. Suppression of MBP-induced proliferation was observed in 13 out of 29 (45%) MS patients; this was significantly (p < 0.05) less compared with 17 out of 19 (89%) healthy individuals. Relative T_reg counts was significantly increased in MS patients (mean ± S.D.; 20 ± 8%) compared with healthy individuals (15 ± 5%). These findings suggest that impaired T_reg function may be involved in pathogenesis of MS.