We had similar difficulties detecting CD19 antigens on B cell CLL patients (and even normal fresh controls) using BD's CD19 conjugated with PerCP. Originally, we were staining patient specimens with CD3-FITC / CD19-PE as part of our CLL panel. When we began to incorporate 3-color techniques into our protocols, we attempted to add CD19-PerCP to the BD kappa-FITC/lambda-PE tube. Even though BD markets two CD19 clones conjugated to PerCP, both reagents were dim or even negative in many patients who were CD19-PE positive. Now we make a cocktail of BD's kappa/lambda with CD20-PerCP. Even though B CLL often demonstrates dim CD20, we have had better luck with this combination in attempting to demonstrate light chain restriction than using the CD19-PerCP. In addition, this combination allows us to target the aberrant dim CD20 cells in the presence of normal B cells. Incidently, we run CD5-FITC / CD20-PE / CD45-PerCP in the CLL panel as well. Good Luck! Cathy Fritschi Sentara Norfolk General Hospital Norfolk, VA
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