UPDATE ON IMMUNOELECTRON MICROSCOPY IN DIAGNOSTIC DERMATOPATHOLOGY AND CUTANEOUS BIOLOGY - 08/09/11

Doi : 10.1016/S0733-8635(05)70116-9

Gundula Schaumburg-Lever, MD ^{^{*
Department of Dermatology, Eberhard Karls University, Tuebingen, Germany}}

Résumé

Not many dermatology departments still have an electron microscope because it is usually not necessary to work up tissue by electron microscopy (EM) to arrive at a histologic diagnosis. Immunohistochemistry (IHC) and molecular biology have replaced diagnostic electron microscopy in most instances (i.e., for the diagnosis of histiocytosis X). The diagnosis of histiocytosis used to require diagnostic electron microscopy until a specific antibody against the CD Ia antigen of Langerhans cells was developed, first for cryostat sections only, but recently for formalin-fixed paraffin-embedded tissue.

In order to evaluate tissue embedded for immunoelectron microscopy (IEM) profound knowledge of routine EM is necessary. For routine EM, the tissue is usually fixed in Karnovsky's fixative containing paraformaldehyde and glutaraldehyde, and the tissue is postfixed in osmium tetroxide and then embedded in Epon or Araldite (Serva, Heidelberg). Therefore, cell membranes, nuclei, and organelles are well preserved, have a nice contrast, and are easy to recognize. Tissue processed for IEM, however, should not be fixed with glutaraldehyde or only fixed with a small amount of glutaraldehyde, and should not be fixed with osmium because both destroy antigen binding sites. The tissue is usually fixed in 3% paraformaldehyde and 0.01% glutaraldehyde or in periodate-lysine-paraformaldehyde (PLP). The preservation of the morphology is acceptable, but the contrast is low; therefore, it is more difficult to recognize morphologic details.

For best results concerning tissue preservation and reliable labeling with antibodies, the tissue should be fixed in PLP, embedded in Lowicryl, KYM (Serva, Heidelberg) at −40°C, and the dehydration of the tissue should be performed by cryosubstitution or cryofixation.^{20Schaumburg-Lever G., Fehrenbacher B., Möller H., et al. Techniques in immuno-electron microscopy: I. Cryosubstitution J Cutan Pathol 1994 ; 21 : 330-338 [cross-ref]

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For which purposes are we using IEM today?

1	Case studies can be complimented by either routine EM or IEM.
2	Results obtained with IHC can be studied further by IEM.
3	Molecular biology techniques and IEM can be very useful to study the pathogenesis of genetic diseases or autoimmune bullous diseases, or for basic science research in general.

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