MONOCLONAL-ANTIBODIES TO HUMAN SPLEEN FERRITIN .1. ISOLATION AND CHARACTERIZATION OF INTERACTIONS WITH ISOFERRITINS AND APOFERRITIN

Three monoclonal antibodies raised against human spleen ferritin were tested for interactions with soluble and immobilized ferritin. Direct enzyme immunoassay was developed to study binding of soluble biotinyla ted ferritin to the antibodies with subsequent isolation of immune com plexes on streptavidin-cellulose. Of all ferritins tested (from human liver, spleen, and heart, and from horse spleen) the monoclonal antibo dies interacted only with L-ferritins (from human spleen or liver), ev idence of their high species and tissue specificity. The monoclonal an tibodies do not bind to subunits of dissociated ferritin suggesting th eir specificity to conformation-dependent epitopes of ferritin. The an tibodies showed greater affinity for iron-deprived (apoferritin) than to native ferritin because of greater conformational mobility of the f ormer. This property causes apoferritin to lose all of its immunoreact ivity when absorbed on polystyrene due to conformational changes on ab sorption These data provide further evidence for conformational nature of the ferritin epitopes specific to the three monoclonal antibodies.