Tregs number consistently increased in CSF of patients with MS compared with healthy controls, but a defect was detected in its suppressor function in RRMS patients associated with a very low expression of Foxp3 mRNA; this is not presented in SPMS patients, where the Tregs suppressor function and Foxp3 expression are normal [28, 49]. The gene discussed is FOXP3; the disease is secondary progressive multiple sclerosis.