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SUMMARYSignal amplification in immunohistochemistry via binding of biotinylated tyramine to proteins near the site of peroxidase-labeled antibodies is a promising new technique, but studies investigating a wide range of markers are lacking. The tyramine amplification technique (TAT) was investigated on 85 antibodies using a simple and fast protocol, and TAT results were compared to those obtained with conventional immunohistochemistry. Using TAT, most of the markers could be 5-to 50-fold further diluted and still showed identical staining results compared with standard stainings (maximal 500-fold). However, the variable reactivity of the different markers with TAT underlines the need for individual testing of every antibody to determine the optimal dilution. Some antibodies against cell adhesion molecules could be demonstrated for the first time in archival, formalin-fixed tissue sections. TAT, if carefully evaluated, offers a revolutionary improvement for modern immunostaining, either to increase sensitivity or primary antibody dilutions (cost reduction). From a methodological point of view, immunohistochemistry has not reached its limits by far and TAT is an important progressive step in this developmental process.(

The proliferative potential of multinucleated Reed-Sternberg-like cells and the process of multinuclear formation were studied on the Hodgkin's-disease-derived cell line HDLM-2. No difference in surface antigen expression was found between mono- and multinucleated cells as determined by immunolabelling with characteristic markers. After sorting and reculture of purified mononucleated cells, polykaryons emerged subsequently in these cultures, indicating that mononucleated cells give rise to multinucleated variants. The morphological observation of mitotic figures and immunostaining with the cell cycle indicators Ki-67 and BrdU provided evidence of DNA synthesis and nuclear division in multinucleated cells. The presence of mitotic figures demonstrated that multinucleated cells are able to undergo synchronous nuclear division. However, while polykaryons were clearly mitotically active and capable of DNA synthesis, the absence of telophases and the failure of active replication suggest a disturbed cytokinesis. Co-cultivation of BrdU-labelled and unlabelled populations did not lead to hybrid polykaryons with negative and positive nuclei. Therefore, multinucleated giant cell formation of HDLM-2 cells appears to involve nuclear endomitosis without cell division rather than cell fusion.

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