A new method to improve the discrimination between lymphocytes and contaminating erythrocytes in flow cytometric analytical techniques.

A method is described for the removal of contaminating erythrocytes from immunofluorescence labelled lymphocyte preparations and allowing accurate gating on the lymphocyte population during flow cytometric analysis. The technique involves an improved erythrolytic fixative combined with the DNA stain propidium iodide permitting non-nucleated cells (i.e., red blood cells) to be gated out during analysis. The erythrolytic fixative was shown not to be detrimental to the major T cell markers detected using indirect immunofluorescence. This method will improve the analysis of blood lymphocytes and their subsets in mononuclear cell preparations and more particularly in samples of body fluids and tissue washings or extracts which may contain variable and often large numbers of erythrocytes.