Amyloids are unsoluble fibrils formed by aggregated proteins. The common structural feature of amyloid fibrils is the β sheet structure. Many proteins with essential functions in our body can become misfolded and start to form amyloid fibrils. These fibrils become visible in the tissue as plaques or deposits, since they are unsoluble and cannot be broken down by the cells. The most widely known Amyloid disease is Alzheimer's disease. Here, two types of plaques are usually found, the extracellular Aβ fibrils and the intracellular aggregates of τ protein, which form the so-called neurofibrillar tangles. Both are related to mutations in the Amyloid precursor protein.
A rare and serious Amyloid disease is systemic amyloidosis, where amyloid plaques form in the whole body. Another Amyloid disease, inclusion body myositis, is mainly characterized by intracellular plaques (inclusion bodies) in muscle fibres.
Protein misfolding is also a problem in Prion diseases like Creutzfeldt Jakob's disease. Prions are misfolded proteins that can induce misfolding in other proteins. All known prions induce the formation of amyloid fibrils in the tissue.
Today, crystal violet or thioflavin stains are used to detect Amyloid fibrils in tissue sections. But these dyes are not very sensitive and interpretation of those stainings is usually done by a pathology expert. To use antibodies against the fibrillated proteins, the amyloid fibrils have to be dissolved so that the antibody can get to its epitope. None of those stainings is suited for use in living tissue. A new type of Amyloid staining is provided by our Amytracker™ dyes.