Immunoelectronmicroscopy: Immunogold and immunoperoxidase compared using a new post-embedding system

Immunogold and immunoperoxidase methods have been compared on ultra-thin sections of the same tissue prepared by a new system of fixation and embedding. Surgically removed human pituitary was fixed in buffered glutaraldehyde/picric acid and, without osmium post-fixation, embedded in a new acrylic plastic, LR White, in order to preserve both antigenicity and ultrastructure. Ultra-thin sections, without any pre-treatment such as etching or trypsin digestion, were than exposed to dinitrophenyl (DNA)-labelled anti-'Synacthen', an antibody to human ACTH. Some of these sections were then stained with colloidal gold using the indirect immunogold staining method and others using a DNP-hapten bridge antibody immunoperoxidase technique. The merits and demerits of the two immunotechniques are discussed.