Clinical relapses of multiple sclerosis are associated with ‘novel’ valleys in natural killer cell functional activity

Natural killer (NK) cells are implicated in the pathogenesis of multiple sclerosis (MS). Nine relapsing–remitting MS (RRMS) patients along with age, sex, and NK responder status matched controls were studied serially. Although the average NK cell functional activity (FA) was not significantly different between both groups, four clinical relapses in RRMS patients were associated with the development of ‘novel’ valleys in FA. These valleys are of greater depth and duration than cyclical valleys observed in both RRMS and controls, precede the onset of clinical attacks, and are observed in RRMS but not controls.