DIFFERENTIATION OF AMYLOID FIBRIL PROTEINS IN TISSUE SECTIONS Two Simple and Reliable Histological Methods Applied to Fifty‐one Cases of Systemic Amyloidosis

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Abstract
The potassium permanganate method and the unlabeled immunoperoxidase (PAP) method were applied for distingushing different types of amyloid fibril proteins in conventionally fixed, paraffin-embedded tissue sections obtained from 51 autopsied cases of systemic amyloidosis and 3 control cases of well-analyzed fibril proteins. All of the 18 cases sensitive to permanganate treamtent, whose amyloid deposits lost completely their affinty to Congo red and birefringence under polarized light, had AA antigenic determinants by the PAP method. All of the remaining 33 resistant cases, where Congo red affinity and birefringence were retained to various degrees if only in minimal areas), were negative for AA antigenicity. This indicated the feasibility of potassium permanganate method for the identification of AA protein based on this criterion of sensitivity. Twenty-eight cases were classified as AA, A.lambda., A.kappa. or AA+[A.kappa.], the remaining 23 cases were unclassified, and there were some discrepancies between the preliminary clinicopathological classification and the protein nature of the amyloid. It is important to differentiate the types of amyloid fibril protein of individual patients because the expedience of selective therapeutic approaches had been suggested. The 2 methods applied herein are handy and useful for this purpose.