Immuno-electron microscopic identification and classification of amyloid in tissue sections by the postembedding protein-A gold method.

Amyloid deposits from 3 patients with amyloid of the AA, A lambda, or A kappa type were investigated on ultrathin sections using the protein-A gold method and affinity purified amyloid-type-specific immunoglobulins. Anti-AA, -A lambda, and -A kappa reacted specifically with the corresponding amyloid fibril visualized by the agglomeration of the gold colloid particles. Therefore, this method can identify and classify amyloid fibrils and can distinguish them from other fibrillar proteins at the electron microscopic level.