Suspend the cells in 1% (w/v) paraformaldehyde in PBS (pH 7.4) at a concentration of 1-2 x 106 cells/ml. Place the cell suspension on ice for 30-60 minutes. Centrifuge cells for 5 min at 300 x g and discard the supernatant. Wash the cells in 5 ml of PBS, then pellet the cells by ...