A novel multicolor immunofluorescence method using heat treatment.

We describe a novel method for immunofluorescent detection of multiple antigens in a single paraffin-embedded tissue section. We hypothesized that if fluorescent dyes are resistant to heat treatment, then thermal inactivation of immunoglobulins during antigen detection procedures might make it possible to use multicolor immunofluorescence detection even if the primary antibodies are from the same species. We found that several fluorescent dyes, including fluorescein isothiocyanate (FITC), Cy3 and Cy5, were resistant to heating at 90 degrees Celsius for 15 min, whereas the antigenicities of the primary antibodies were lost completely. This novel method, which uses heat treatment between staining steps, has great advantages for multicolor immunofluorescence because unlabeled primary antibodies from the same species can be used. Therefore, by using this method not only 3 unlabeled mouse monoclonal antibodies but also 3 unlabeled rabbit antisera can be used as primary antibodies for multicolor immunofluorescence.