As research into interferon beta (IFN-b) and neutralizing antibodies (NAbs) continues, two recent studies report additional evidenceof NAbsaffecting IFN-b action in vivo, each from a different perspective. The first looks at the effect of NAb on the bioavailability of IFN-b-1b while the second examines the effect of IFN-b-1b "on NK [natural killer] cell function and phenotype... and their relationship to disease activity assessed both clinically and with serial MRI."⁹ Both studies provide new evidence of NAbs modifying the activity of IFN-b.

Deisenhammer et al. measured MxA blood levels, NAb titers and IFN-b serum binding antibodies (SBA) in patients on IFN-b-1b and in control subjects in order to "investigate the effect of NAb on the bioavailability of IFN-b-1b as well as the relationship between SBA and NAb." ⁷

Results from the study were as follows:

	Number of samples	Median MxA Concentration	% of samples with SBA
From IFN-b-1b treated patients	134
NAb negative	84	4.09 ng/105 PBL	49.0%
NAb positive (titer >20)	21	0.36 ng/105 PBL	10.0%
Detectable NAb (titer 10-20)	29	2.37 ng/105 PBL	79.0%
From control patients	54	0.27 ng/105 PBL	0.0%