A single laser flow cytometry method to evaluate the binding of three antibodies.

Here we describe a flow cytometry method which permits the collection of data regarding three staining parameters of a single cell from a suitable combination of dual parameter stainings using PE- and FITC-labelled mAbs and a single argon laser. The technique neither requires a third dye with non-overlapping emission spectra nor a second light source. In order to test the accuracy of this method, we compared data calculated using this triple parameter analysis with data obtained by double staining a presorted population homogeneously positive for one parameter. In experiments using either resting or in vitro activated T cells, the percentages obtained with both methods were identical (P greater than 0.05). Using this method we tested which T cell sub-subpopulation is responsible for the weak CD25 (IL-2R alpha) expression constantly associated with freshly isolated human T cells and concluded that it is predominantly expressed on the CD4+ CD45RO+ (CD4 positive memory) T cell subpopulation.