Immuno electron microscopy – tracking the sub‐cellular localization of antigens in high resolution

Abstract Purpose Any antigen to which an antibody can be generated can be localized, at sub‐cellular level and viewed under very high magnification by immuno‐electron microscopy (immune‐EM). The applications of EM immunocytochemistry are very wide ranging. Methods A particular antigen is localized by primary antibody (monoclonal or polyclonal) within a tissue. The primary antibody is visualized using a secondary antibody, the gold conjugates of 5 or 10nm size. The gold particles are opaque and can be seen under an electron microscope. The antibody can be used on pre‐embedded or post embedded tissue. In the pre‐embedding method, a fresh thin piece of tissue is treated with primary and secondary antibodies. In the post‐embedding method, primary and secondary antibodies are used on ultrathin sections. The immunocytochemistry is also carried out on cryosection. Double immune labeling is also carried out by some authors. Results A number of extracellular matrix proteins and non‐collagenous glycoproteins, such as collagen, elastin, fibronectin, laminin, keratan sulphate proteoglycan, BKS1, chondroitin sulphate, keratoepithilin have been demonstrated by the immuno‐EM procedure. A number of cellular proteins such as keratoepithelin and actin were also shown by immuno‐EM. Conclusion Immuno‐EM is a very powerful technique since it combines the specificity and flexibility of immunocytochemistry with the resolution at high magnification of electron microscopy. Acknowledgement: Supported by National Plan for Science and Technology, KSU, Riyadh.