Immunohistochemical profiles of 30 monoclonal antibodies against cytokeratins 8, 18 and 19 - Second report of the TD5 workshop

In the first report of the TD5 workshop (TD5-1), the epitope specificities of 30 different monoclonal antibodies against cytokeratins 8, 18 and 19 wer e determined. This second report presents the immunohistochemical profiles of these antibodies using human appendix and normal skin for evaluation. Ea ch antibody was tested by one or two different laboratories recruited from the Dutch Working Group on Immunohistochemistry and Cytochemistry. Eight di fferent laboratories participated. The histological specimens were pretreat ed by the participants in three different ways for immunohistochemistry: mi crowave antigen retrieval in citrate buffer, enzymatic digestion to restore epitope exposure, no specific treatment (untreated paraffin-embedded sampl es), and tested blind ly without knowledge of cytokeratin or epitope specif icity of the antibodies at three different concentrations of 50, 10 and 1 m ug/ml. Most of the tested antibodies (29/ 30) were useful in at least one p retreatment method, with microwave antigen retrieval being the most sensiti ve approach. For some antibodies, very high backgrounds were observed. Furt hermore, it can be concluded that 11 MAbs performed well using all three st aining protocols, including untreated paraffin-embedded sections. Interesti ngly, all the antibodies with documented selected specificity towards cytok eratin 8 (i.e. 178, 191, 199, 202 and 206) are reactive with an immunodomin ant region corresponding to amino acids 340-365 on cytokeratin 8, which evi dently is well-suited as target for immunohistochemical interactions. Simil arly, three antibodies with the same capacity to react with untreated sampl es had specificity against cytokeratin 19 (i.e. 179, 197 and 204) in the co rresponding region in this filament, i.e. amino acids 311-335, or the KS 19 .1 epitope. None of the six antibodies against the other major cytokeratin 19 epitope (BM 19.21) were found useful for immunohistochemistry on untreat ed samples. The overall conclusions from the present investigation are that all cytokeratin-8-specific antibodies with defined epitope specificities w ere very useful. Only one of the major two epitopes on cytokeratin 19 seems to be available for efficient immunohistochemistry. Cytokeratin 18 exposes some epitopes outside the immunodominant region reactive with the antibodi es 190, 203 and 205 which can be used for untreated samples. The implicatio ns of these findings are of significance both for diagnostic histopathology and for the biology of tumor marker epitope expression in tissues, Copyrig ht (C) 2000 S. Karger AG, Basel.