Lack of effects of IVIg on tau pathology in 3xTg-AD mice. (A) Brain sections of 12-month-old mice at sacrifice (n = 3 per group) were stained for tau using anti-human tau antibody (HT-7) after a 3-month treatment with IVIg or vehicle (ctrl) and imaged with fluorescence. Sections shown are from the CA1 region of the hippocampus (bregma approximately −3.5). Scale bar = 100 μm. Green, human tau; blue, DAPI. (B) Immunoblot analyses were performed on protein fractions from the parietotemporal cortex of 3xTg-AD mice. Ratios of phosphorylated tau/human total tau showed the absence of protective effects of IVIg injections. Total human tau and phosphorylated tau were analyzed in the cytosolic (left) and insoluble fractions (right). Representative results are presented for mice treated for 3 months and sacrificed at the age of 12 months and 16 months (n = 10 to 13 animals per group). Values are expressed as the mean ± SEM. Statistical analysis: unpaired Student t-test with Welch’s correction. Examples of immunoblots in both fractions (bottom). The homogeneity of sample loading in cytosolic fraction was determined by protein quantification and actin staining. 3xTg-AD, triple-transgenic mouse model of Alzheimer’s disease; ctrl, control; DAPI, 4′, 6-diamidino-2-phenylindole; IVIg, human intravenous immunoglobulin.