Isolation of human splenic macrophages and lymphocytes by countercurrent centrifugal elutriation

Certain tissues, such as the spleen, are rich sources of mononuclear phagocytes (MP); however, separating the phagocytes from tissues and removing the contaminating cells have been difficult. We report here a method for the extraction and purification of human splenic MP that employs gentle homogenization of splenic fragments with a Tenbroeck tissue homogenizer, controlled digestion with purified collagenase to free MP from splenic stroma, incubation with DNase to dissociate cell clumps and purification by countercurrent centrifugal elutriation (CCE). With homogenization and enzymatic digestion most of the splenic nonspecific-esterase-positive cells are freed into suspension as determined by morphometric analysis of 2 micron sections from plastic embedded spleen stained for alpha-naphthyl butyrate esterase (ANB). Overall cell recovery after homogenization and enzyme treatment is 56 +/- 7%; no selective cell loss occurs as determined by differential cell counts at each purification step. CCE of up to 3 X 10(9) treated spleen cells results in recovery of 63 +/- 6% of the elutriated cells and separates nearly 50% of the recovered MP into enriched fractions. These MP are morphologically intact as determined by light and electron microscopy and are actively phagocytic. Highly purified (96%) autologous splenic lymphocytes are a useful by-product of this separation technique.