Quantification of the relative fluorescence intensity of CD44 on cells and protein-coated microspheres by flow cytometry.

<p>LS174T colon carcinoma cells or HL60 human myeloid cells were treated with either PDGF (100 ng/ml) or PBS diluent for 48–72 h. LS174T CD44 (A) or HL60 CD44s (B) was immunoprecipitated using the anti-CD44 mAbs 2C5 and 515, respectively, and adsorbed on polystyrene microspheres. CD44 expression on cells or microspheres coated with immunopurified CD44 from the corresponding cell type was quantified by single-color immunofluorescence and flow cytometry using the PE-conjugated anti-CD44 mAb 515. Background levels were determined by incubating cell or microsphere suspensions with the properly matched PE-conjugated mouse IgG isotype control antibody. Flow cytometry histograms are representative of >4 independent experiments. A minimum of 3000 events (i.e., CD44-coated microspheres or CD44-expressing cells) was analyzed on a given experiment.