Regulatory peptide immunocytochemistry at light- and electron microscopical levels

Summary Immunocytochemical techniques applied at both light- and electron microscopical levels are valuable in the study of regulatory peptide distribution in normal and diseased tissue, whether in the form of sections or whole cell preparations. Successful immunolocalisation depends on 1) adequate preservation of the peptide antigen and the tissue structure in which it resides; 2) a suitably specific and sensitive labelled antibody detecting system. In general, peptides are stable molecules, most of which retain their antigenicity after conventional cross-linking fixation and tissue processing, allowing standard immunocytochemical methods to be used for light- and electron microscopy. Regulatory peptides are derived from precursor molecules and several families of structurally similar peptides are now generally recognised. Region-specific antibodies may be needed to overcome problems of cross-reactivity or to identify a bioactive form in the presence of its precursor. Multiple co-localisation of different related and unrelated peptides in the same cell or even storage granule is now recognised and can be identified by immunocytochemistry.