Characterization of ferritin and ferritin-binding proteins in canine serum

Ferritin and ferritin-binding proteins in canine serum were characterized. A certain percentage of ferritin in canine serum, but no tissue ferritin, w as precipitated by centrifugation at 16,000 x g for 30 min. The precipitate d ferritin was found to contain two subunits corresponding to the H and L s ubunits of canine liver ferritin by immunoblotting, the H subunit being pre dominant. More ferritin was precipitated from canine sera which had been in cubated with anti-rat liver ferritin antibody than from untreated sera, and the H chain also predominated. To evaluate the possibility that the autoan tibody was responsible for the precipitation of canine serum ferritin, the ferritin-binding activities of canine antibodies were examined using liver ferritin-coated microtiter plates and alkaline phosphatase-labeled antibodi es specific for canine IgM, IgA, and IgG heavy chains. The results showed t hat IgM and IgA, but not IgG, had considerable ferritin-binding activities. Given these results, we suggest that there is H-chain-rich isoferritin in canine serum, and that ferritin exists as an immune complex.