Immunochemical typing of amyloid deposits after microextraction from biopsies.

A simple procedure for identifying amyloid fibril proteins in biopsies and small tissue fragments is described. Amyloid fibrils from 21 patients with amyloid deposits (including 6 controls) were freed from soluble proteins and concentrated by a microextraction technique. The solubilized amyloid fibril proteins were then examined by immunodiffusion with antisera directed against amyloid fibril proteins (AA, A lambda, A kappa, ASc1, AF), cystatin C and beta 2-microglobulin. 9 out of 11 specimens with inconclusive immunohistochemical results, 5 other specimens, and 6 control specimens could clearly be typed with this method. Microextraction followed by immunochemical identification, therefore, can be considered an additional option for chemical amyloid classification in those cases in which immunohistochemical typing does not yield unequivocal results.