After washing in medium 199 (GIBCO-BRL) the livers were aseptically minced into small fragments (about 1mm3) and suspended in fresh medium for 1–2 min. This process was repeated 3–4 times to get rid of most red blood cells. The liver
tissues were incubated in PBS (Ca2+ and Mg2+ free) solution containing 1 mg/mL collagenase (type II, GIBCO-BRL) at 37 °C in a shaking water bath for 10–15 min with frequent pipetting to facilitate cell dissociation.