It has been reported that a subset of immune cells known as Tregs (characterized by expression of the protein CD4 and high levels of expression of the protein CD25), which suppresses the function of aggressive immune cells, is defective in individuals with MS, and that this contributes to the progression of the disease.

However, it has recently been shown that if CD4+CD25high cells are divided into cells expressing high and low levels of the protein CD127 only the CD4+CD25highCD127low cells have suppressive capability. Thus, Jean-Paul Soulillou and colleagues, at INSERM U643, France, compared the suppressive capabilities of CD4+CD25highCD127low cells from individuals with MS and healthy individuals.

Surprisingly, they found that these cell populations were equally effective suppressors of aggressive immune cells when analyzed in vitro.

Data therefore indicates that the suppressive function of Tregs (when characterized as CD4+CD25highCD127low) is not defective in individuals with MS, suggesting that this defective Treg function is not a factor that contributes to the development of this debilitating autoimmune disease. 

Full data: http://content.jci.org/articles/view/35365 (if you like math)