Biological activity of glatiramer acetate on Treg and anti-inflammatory monocytes persists for more than 10years in responder multiple sclerosis patients.

Glatiramer acetate (GA) is a widely used treatment for multiple sclerosis (MS), with incompletely defined mechanism of action. Short-term studies suggested its involvement in the modulation of anti-inflammatory cytokines and regulatory T cells (Treg), while long-term effect is still unknown. To investigate this aspect, we analyzed by flow-cytometry peripheral-blood Treg, natural killer (NK), CD4 and CD8 T-cells and anti-inflammatory CD14+ CD163+ monocytes from 37 healthy donor and 90 RRMS patients divided in untreated, treated with GA for 12months and from 34 to 192months. While NK, CD4 and CD8 T-cells did not show any significant differences among groups over time, we demonstrated that GA increased the anti-inflammatory monocytes and restored the Treg level in both GA-treated groups. Both these effects are a characteristic of responder patients and are observed not just in short-term but even after as long as a decade of GA treatment.