Relapsing-remitting multiple sclerosis patients exhibit differential natural killer functional subpopulations

Background Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) and has been known as T-cell mediated. However, the contribution of multiple cell types, notably natural killer (NK) cells, has also been reported. Aim To quantify circulating total NK cells and its subpopulations, CD56 dim and bright, and to characterize the functional phenotype and IFN-gamma and TNF-alpha production in relapsing-remitting patients treated with IFN-beta and in apparently healthy controls. Results CD56(bright) NK cells were found to be the least represented subpopulation. In relapse patients, the frequencies of IFN-gamma-producing NK cells and their subpopulations were significantly decreased. In remission patients, CD56(dim) NK cells expressed high levels of HLA-DR and CD54. Conclusion These results suggest that remission RRMS patients, although in an inactive stage of MS, present circulating NK cells with an activation phenotype, supporting the idea that NK cells may be relevant mediators in the MS pathophysiology.