Staining of a cytospin preparation of peripheral blood mononuclear cells isolated from buffycoat. Cells were left to air dry and then fixed with cold acetone (90 seconds) and blocked with PBS containing 1% FCS and 0.1% saponin (blocking buffer) for 20 minutes. Cells were then washed twice in PBS and incubated with ab72012, diluted 50µg/ml: in blocking buffer, for 1 hour at room temperature. Cells were washed twice in PBS followed by incubation for 30 minutes with the FITC-labeled secondary antibody. Finally, cells were washed and nuclear counterstained with DAPI. The antibody selectively recognizes polymorphonuclear cells.