In this study Kastrukoff et al. examined the role of natural killer (NK) cells in multiple sclerosis, the effect of IFN-b treatment on NK cell activity and this activity's relationship to disease progression in relapsing-remitting multiple sclerosis (RRMS) patients.

Researchers found, in patients treated with high-dose (8 MIU) IFN-b, an inverse relationship between the total number of active lesions and mean NK cell functional activity (FA). Specifically, they reported "A 10-U (percent specific release) increase in NK FA is associated with a decrease of approximately 22% in the number of active lesions per unit time."⁹ This relationship was "significantly different from the positive relationship identified among placebo patients. ... [W]e interpreted the positive relationship to indicate that RRMS patients with high mean NK cell FA were at greater risk for the development of active lesions."⁹