[Monoclonal antibodies to human spleen ferritin. I. Preparation and study of the interaction with isoferritin and apoferritin].
Three monoclonal antibodies to human spleen ferritin were produced and their interaction with soluble and immobilized ferritins studied. An immunoassay was developed to monitor the interaction of soluble biotinylated ferritin and the antibody with subsequent separation of the soluble complexes on streptavidin-cellulose. Analysis of immunoreactivities of a series of isoferritins (human liver, spleen, heart and equine spleen ferritins) revealed that all the three monoclonal antibodies bound to only human L-type ferritins (spleen and liver ferritins), suggesting a high species- and tissue specificity of these antibodies. The monoclonal antibodies were specifically directed against conformation-dependent antigenic determinants as could be evidenced from the lack of their binding to the subunits of the dissociated ferritin. The affinity of the monoclonal antibody for the ferritin deprived of iron (apoferritin) was higher than that for native ferritin due to the greater conformational flexibility of the apoferritin molecule. The latter property may underly a complete loss of immunoreactivity by the apoprotein adsorbed on the polystyrene surface as a result of conformational changes induced in the apoferritin molecule by adsorption. These findings provide additional support for recognition by all of the three antibodies of conformational antigenic epitopes in the ferritin molecule.