Aggregates of hyperphosphorylated tau protein are found in a group of diseases 
called tauopathies, which includes Alzheimer's disease. The causes and 
consequences of tau hyperphosphorylation are routinely investigated in 
laboratory animals. Mice are the models of choice as they are easily amenable to 
transgenic technology; consequently, their tau phosphorylation levels are 
frequently monitored by Western blotting using a panel of monoclonal/polyclonal 
anti-tau antibodies. Given that mouse secondary antibodies can recognize 
endogenous mouse immunoglobulins (Igs) and the possible lack of specificity with 
some polyclonal antibodies, non-specific signals are commonly observed. Here, we 
characterized the profiles of commonly used anti-tau antibodies in four 
different mouse models: non-transgenic mice, tau knock-out (TKO) mice, 3xTg-AD 
mice, and hypothermic mice, the latter a positive control for tau 
hyperphosphorylation. We identified 3 tau monoclonal antibody categories: type 
1, characterized by high non-specificity (AT8, AT180, MC1, MC6, TG-3), type 2, 
demonstrating low non-specificity (AT270, CP13, CP27, Tau12, TG5), and type 3, 
with no non-specific signal (DA9, PHF-1, Tau1, Tau46). For polyclonal anti-tau 
antibodies, some displayed non-specificity (pS262, pS409) while others did not 
(pS199, pT205, pS396, pS404, pS422, A0024). With monoclonal antibodies, most of 
the interfering signal was due to endogenous Igs and could be eliminated by 
different techniques: i) using secondary antibodies designed to bind only 
non-denatured Igs, ii) preparation of a heat-stable fraction, iii) clearing Igs 
from the homogenates, and iv) using secondary antibodies that only bind the 
light chain of Igs. All of these techniques removed the non-specific signal; 
however, the first and the last methods were easier and more reliable. Overall, 
our study demonstrates a high risk of artefactual signal when performing Western 
blotting with routinely used anti-tau antibodies, and proposes several solutions 
to avoid non-specific results. We strongly recommend the use of negative (i.e., 
TKO) and positive (i.e., hypothermic) controls in all experiments.