GASTROINTESTINAL AAPOAII AND SYSTEMIC AA-AMYLOIDOSIS IN AGED C57BL KAMICE - AMYLOID-TYPE DEPENDENT EFFECT OF LONG-TERM IMMUNOSUPPRESSIVE TREATMENT/

The light microscopic and immunohistochemical features of a novel loca lized senile amyloidosis in the gastrointestinal tract of C57BL/Ka mic e are described. Senile gastrointestinal amyloidosis was predominantly found in the lamina propria of the ileum, cecum and stomach and infre quently in other segments of the gastrointestinal tract. The Congo red affinity of the senile amyloid was sensitive to potassium permanganat e pretreatment. The amyloid did not react with anti-AA and anti-immuno globulin antisera, but stained positively for apoAII, a major apolipop rotein of high density lipoproteins. A similar type of amyloid, termed AApoAII, has recently been described in a systemic form of senile amy loidosis in mice. In the present study, we investigated the effect of long-term immunosuppressive treatment on the incidence of systemic AA- amyloidosis and gastrointestinal AApoAII-amyloidosis in aged C57BL/Ka mice. Gastrointestinal amyloidosis occurred in 60% of the control mice , but significantly less in mice of the immunosuppressed groups. In co ntrast, systemic AA-immunoreactive amyloidosis was only found in mice that were given immunosuppressive treatment. There was no codeposition of AA and AApoAII-amyloid. These findings indicate that immunosuppres sive drugs have a profound effect on the incidence as well as the type of amyloidosis in C57BL/Ka mice.