Although RD3 and RD4 were originally reported to label human brain sections efficiently following a standard antigen retrieval protocol (heat-induced epitope retrieval (HIER) in citrate buffer pH 6.0) [134], very few subsequent studies appear to have obtained immunolabelling with this protocol, e.g. [61], and others have specified that neither antibody labels human tauopathy brain sections in the absence of pre-treatment with formic acid and autoclaving [42]. Here, RD3 is linked to tauopathy.