GAD1 and stiff-person syndrome: The enzymatic activity did not differ when rhGAD65 was incubated with serum from GAD-alum- (median 90 %, range 42-100) and placebo-treated patients (median 91 %, range 65-100), but was significantly higher compared to GAD65 incubated with control serum from a SPS patient (median 20 %, range 19-24; p<0.001; Fig. 5C).