Some recent developments in immunocytochemistry.

Immunocytochemistry has become an indispensable tool both in basic biomedical research and in diagnostic histopathology. Several recent innovations have led to improvements in the sensitivity; specificity and precision of these techniques. Numerous modifications of the original methods have been developed, many with increased sensitivity. In particular, methods using protein A or the avidin-biotin complex as second steps appear to be promising. New methods for the quantitative determination of sensitivity have become available. The introduction of monoclonal antibodies as immunocytochemical reagents appears to be a major improvement. New methods of immunochemical analysis, such as immunoblotting and immunospotting of antigens extracted from tissue specimens, allow the molecular composition of immunoreactive antigenic sites in a tissue to be analysed. The accuracy of localization in immunoelectron microscopy has been improved significantly through the use of ultracryotomy of unfixed tissue in combination with colloidal gold particles as a label. In addition, gold particles can be counted and thus allow relatively simple quantification of the immune reaction. Using flow cytometry, especially in combination with monoclonal antibodies, quantitative immunofluorescence has become feasible.