Immunohistochemical Detection of Amyloid AA in Formaline-Fixed Paraffine-Embedded Rectal Biopsies with the Monoclonal Anti-Human Saa Antibody Reu.86.2

Abstract

The present study addresses the reliability of a monoclonal anti-human SAA antibody (Reu. 86.2) to detect amyloid AA in formaline-fixed paraffine-embedded rectal biopsies. A total of 34 rectal biopsies obtained from amyloidotic patients from 1986 until februari 1990 were positive for amyloid in the Congo red (CR) stain. Pretreatment with KMnO4 eliminated CR staining in 30 specimens (AA-amyloid) whereas in 4 biopsies CR staining was resistent to KMnO4 (non-AA). A murine monoclonal antibody (Reu.86.2) was raised against apo-SAA coupled to Helix Pomatia Haemocyanin. After pretreatment with 0.1% protease routine paraffine sections were incubated with Reu.86.2 as the first layer and peroxidase-conjugated Rabbit anti-Mouse antibody as the second. All 30 KMnO4 sensitive specimens showed moderate or strong reactivity in immunostaining with the monoclonal antibody (in these biopsies the intensity of CR staining was moderate or strong in 18 and weak in 12). Twenty CR-negative controls and all 4 KMnO4-resistent biopsies were negative in immunohistochemistry with Reu.86.2. In conclusion, immunohistochemistry with monoclonal anti-SAA antibody Reu.86.2 is an easy and highly reliable method to detect amyloid AA in rectal biopsies.