Experimental study on secondary amyloidosis associated with chronic arthritis

Various organs from rabbits immunized with heat-killed E. coli 0:14 to induce chronic polyarthritis resembling rheumatoid arthritis (RA) were examined for amyloid deposition since amyloidosis is a frequent feature of long-standing RA. Amyloids were confirmed mainly by polarizing as well as nonpolarizing light microscopy after Congo red staining and partly by electron microscopy and immunoperoxidase technique. Amyloid deposits after an additional 2 months from the first appearance of arthritis were most frequently found in the spleen and kidneys suggesting secondary amyloidosis. Amyloidosis was observed in 36% of 75 arthritic rabbits. The incidence of amyloidosis was significantly higher in the arthritic rabbits than in the non-arthritic rabbits (p less than 0.05). This suggests that prolonged sensitization with heat-killed E. coli 0:14 containing endotoxic substance participates in the formation of both arthritis and amyloidosis.