Signal amplification in flow cytometry using biotin tyramine.

BACKGROUND: Catalysed reporter deposition (CARD) has been successfully used as a means of signal amplification in solid-phase immunoassays. The procedure relies on the use of horseradish peroxidase (HRP)-conjugated reagents--normally antibodies-in conjunction with substituted phenolic compounds such as biotin tyramine. The HRP catalyses deposition of biotin tyramine around the site of enzyme activity, and streptavidin-HRP can then be added to generate an amplified HRP signal. The possibility of using this technique for solution-phase amplifications has been suggested but not yet demonstrated.
METHODS: This paper describes the application of CARD to signal enhancement in flow cytometry. The specific examples described here are those of anti-human CD4 and anti-human CD36 antibodies binding to either human lymphocytes or mixed mononuclear cells.
RESULTS: Optimum biotin tyramine concentrations were evaluated, and a fivefold increase in signal was observed over standard detection of the anti-human CD4 antibody with anti-mouse-fluorescein isothiocyanate (FITC). In the example using the anti-CD36 antibody, the biotin tyramine treatment was repeated, resulting in an additional 2.5-fold signal amplification.
CONCLUSIONS: The technique described in this report provides a method of amplifying the signals achieved by standard flow cytometry detection reagents.