Detection of mast cells and basophils by immunohistochemistry

Staining cells or tissues with basic dyes was the mainstay of mast cell and basophil detection methods for more than a century following the first identification of these cell types using such methods. These techniques have now been largely supplanted by immunohistochemical procedures with monoclonal antibodies directed against unique constituents of these cell types. Immunohistochemistry with antibodies specific for the granule protease tryptase provides a more sensitive and discriminating means for detecting mast cells than using the classical histochemical procedures; and employing antibodies specific for products of basophils (2D7 antigen and basogranulin) has allowed detection of basophils that infiltrate into tissues. The application of immunohistochemistry to detect more than one marker in the same cell has underpinned concepts of mast cell heterogeneity based on differential expression of chymase and other proteases. The double-labelling procedures employed have also provided a means for investigating the expression of cytokines and a range of other products. Protocols are here set out that have been used for immunohistochemical detection of mast cells and basophils and their subpopulations in human tissues. Consideration is given to pitfalls to avoid and to a range of alternative approaches.