Effect of IFNbeta and anti-IFNbeta antibodies on NK cells in multiple sclerosis patients.

We analysed longitudinally the numbers of CD3-CD16+ (natural killer cells, NK) and CD3-CD57+ cells (a subset of NK) in 15 IFNbeta1b- and 12 IFNbeta1a-treated relapsing-remitting multiple sclerosis (RRMS) patients. IFNbeta1b (Betaferon)-treated RRMS patients showed a rapid and marked reduction in the number of both NK subsets which started 1 month after therapy initiation, and reached highest significance after 3 months (P=0.000); however, figures reverted to pre-treatment values following the appearance of anti-IFNbeta antibodies. In IFNbeta1a (Avonex)-treated RRMS patients, the decrease in both CD3-CD16+ and CD3-CD57+ cell number was slower but more persistent; anti-IFNbeta antibodies were only rarely detected in these patients, and at lower titers than in IFNbeta1b-treated ones. Our findings suggest that NK cells might be one of the major immunological targets of IFNbeta-based treatments.