Effects of tissue fixation conditions and protease pretreatment on immunohistochemical performance of a large series of new anti-keratin monoclonal antibodies: value in oncopathology.

A comparative study with 21 recently raised monoclonal antibodies (3 of which are reported here for the first time) to human keratin polypeptides was performed on a wide range of paraffin-embedded tissues and tumors, aimed at the examination of effects of four different fixatives and protease pretreatment on the immunohistochemical detection of keratins. Our data demonstrated that: (a) formaldehyde-based fixatives modified by acidification and/or addition of methanol gave results superior to those achieved by routinely used formol saline; (b) relatively rare antibodies (4 out of 21) could be identified which gave reliable immunostaining patterns even on routine formalin-fixed material; (c) a proteolytic digestion step preceding the immunostaining was beneficial for the performance of the majority of antibodies in our panel. Additional options which could potentially lead to further improvement of keratin immunohistochemistry in paraffin embedded specimens are also suggested. This work provides the necessary basis for wider application of the anti-keratin antibodies of the C-series in both routine oncopathology and research-oriented retrospective studies.