Dendritic cell, monocyte and T cell activation and response to glatiramer acetate in multiple sclerosis

Background: Treatment with glatiramer acetate (GA) modestly decreases disease activity in multiple sclerosis (MS). The mechanism of action is incompletely understood and differences in the response to treatment between individuals may exist. Objective: To study the activation of CD4+ T cells, monocytes and dendritic cells (DC) in relation to disease activity in MS patients treated with GA. Methods: Flow cytometry was used to study the activation of CD4+ T cells and T cell subsets (CD25(high) and CD26(high) cells), monocytes and DCs in a cross-sectional study of 39 untreated and 29 GA-treated MS patients, the latter followed prospectively for one year. Gd-enhanced magnetic resonance imaging (MRI) studies were conducted in all patients. Disease activity was assessed as relapses. Results: The median percentage of DCs expressing CD40 was 10% in untreated MS patients and 5.9% in GA-treated patients (Bonferroni-corrected p=0.0005). The hazard ratio of relapse was 1.32 (95% confidence interval 1.05-1.64) per 1% increase in CD40+ DCs. Patients treated with GA had fewer CD4+ T cells expressing surface markers associated with T helper type 1 effector responses and more CD4+ T cells expressing surface markers associated with regulatory, naive or central memory T cell populations, but CD4+ T cell activation was not related with relapse risk. Conclusions: MS patients treated with GA show prominent changes in circulating antigen-presenting cells and CD4+ T cells. Expression of CD40 on DCs is significantly lower and associated with relapse risk in MS patients treated with GA.