Human ferritin: effects of antigen source and fixation on leucocyte staining by immunoperoxidase technique

The localization of ferritin was studied in peripheral blood cells and variously fixed tissues with the antibodies against ferritins isolated from human heart and spleen. The unlabelled antibody enzyme method (PAP) was used to detect the binding sites of antibodies. In peripheral blood cell smears both antisera gave rise to strong staining of polymorphonuclear (PMN) cell cytoplasm, whereas the monocytes stained relatively weakly. There were no staining differences between the two antisera. In human spleen sections the spleen ferritin antiserum stained the PMN cells and sinusoidal lining cells, whereas the heart ferritin antiserum stained only PMN cells. Neither of the two antisera stained monocytes in the spleen sections. This finding was observed in specimens fixed in Bouin's fixative, Baker's fixative and neutral formalin. However, the immunoreactivity of ferritin was totally destroyed by some other fixatives (Carnoy's fixative, formol sucrose and glutaraldehyde). These results suggest that ferritin is more readily released from monocytes than from PMN cells, and that mature spleen macrophages contain antigenic determinants of ferritin that are recognized only by anti-spleen ferritin antiserum.