ACCUSPIN™ System-HISTOPAQUE®-1077 employs centrifuge tubes specially designed with two chambers separated by a porous high-density polyethylene barrier ("frit"). The lower chamber contains HISTOPAQUE®-1077 which allows the addition of anticoagulated whole blood without risk of mixing with the separation medium. On centrifugation, the whole blood descends through the frit to contact with the HISTOPAQUE®-1077 below the frit, giving a clear separation of the blood components. The erythrocytes aggregate and the granulocytes become slightly hypertonic, increasing their sedimentation rate, resulting in pelleting at the bottom of the ACCUSPIN tube. Lymphocytes and other mononuclear cells, i.e., monocytes, remain at the plasma-HISTOPAQUE®-1077 interface.