Intravenous immunoglobulin (
IVIG) products are prepared from plasma
immunoglobulins from healthy donors. Pilot studies suggest that
IVIG may stabilize cognitive functioning in patients with mild-to-moderate
Alzheimer's disease. This study measured
antibodies to recombinant human
tau protein in the
IVIG products
Gammagard (Baxter),
Gamunex (Talecris), and Flebogamma (Grifols). Anti-tau
antibodies were measured by ELISA, subtracting
IVIG's polyvalent binding from its binding to tau-coated wells to calculate specific anti-tau antibody levels. Because polyvalent binding of
IVIG products may interfere with ELISA measurement of their specific antibody levels, the percentage of binding of each
IVIG product to tau-coated wells that was specific for tau was also determined. Specific anti-tau
antibodies were detected in all three
IVIG products, with significant differences between these products (p<0.001) even when Flebogamma's anti-tau
antibodies were doubled to account for its preparation as a 5%
solution vs. 10% solutions for
Gammagard and
Gamunex (means:
Gammagard, 3.1 μg/ml;
Gamunex, 2.5 μg/ml; Flebogamma, 1.2 μg/ml). The percentages of each
IVIG product's specific binding to tau-coated wells also varied between the various products (p<0.001) and between all pairs of
IVIG products (means:
Gammagard, 73.1%; Flebogamma, 54.5%;
Gamunex, 37.4%; p<0.01 for all pairwise comparisons). These findings indicate that
IVIG products contain specific anti-tau
antibodies. The concentrations of these
antibodies and the percentages of specific binding of
IVIG to tau-coated wells vary between
IVIG products. Further studies are indicated to determine if
IVIG also contains
antibodies to pathologic forms of tau.