Page 211 - Veterinary Immunology, 10th Edition

VetBooks.ir Protein Misfolding Diseases

Amyloidosis is the name given to the deposition of insoluble
proteins in body organs. These deposits appear as amorphous,

eosinophilic, hyaline proteins in cells and tissues (Fig. 7.10).
Amyloid proteins are produced as a result of errors in the folding of
newly formed protein chains. These misfolded chains eventually
aggregate to form insoluble fibrils. Amyloid proteins consist of
protein fibrils, formed by peptide chains cross-linked to form β-

pleated sheets (Fig. 7.11). This molecular conformation makes
amyloid proteins extremely insoluble and almost totally resistant to
proteases. Consequently, once deposited in cells or tissues, amyloid

deposits are almost impossible to remove. Amyloid infiltration
eventually leads to gradual cell loss, tissue destruction, and death.
Amyloidosis may be systemic when it involves multiple organs, or
it may be localized, involving only a single organ.

FIG. 7.10 Secondary amyloid deposited in a glomerulus. The red
dye (Congo red) specifically binds to amyloid fibrils. Original
magnification ×400.

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