Elevated CD40 ligand expressing blood T-cell levels in multiple sclerosis are reversed by interferon-beta treatment

Myelin protein reactive CD4(+) T cells are considered to be involved in the proposed immunopathogenesis of multiple sclerosis (MS). One particularly i mportant molecule for T-cell activation is the CD40L (gp39) that is express ed on the surface of T cells. This study focuses on the CD40 and the CD40L expression on mononuclear cells prepared from blood from patients with MS, other neurological diseases (OND) and healthy subjects. Immunostaining foll owed by a three channel flow cytometry was adopted. Patients with MS had hi gher levels of CD3(+)CD40L(+), CD4(+)CD40L(+) and CD8(+)CD40L(+) T cells co mpared to patients with OND and healthy subjects. Cross-sectional compariso ns revealed that the elevation of CD40L(+) T cell subtypes was confined to the patients with untreated MS and not observed in the patients with MS tre ated with interferon-beta (IFN-beta). Follow up studies showed that levels of CD3(+)CD40L(+) and CD4(+)CD40L(+) T cells decreased in individual patien ts after the initiation of the IFN-beta treatment. The enhanced expression of CD40L on CD3(+), CD4(+) and CD8(+) T cells in patients with MS may impli cate a role for this molecule in disease immunopathogenesis.