[8] Purification and cryopreservation of phagocytes from human blood

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Three types of phagocytic cell are found in human blood: monocytes, neutrophilic granulocytes, and eosinophilic granulocytes. For their separation, both biological and physical properties of the cells can be used. The positive selection of phagocytes can be achieved by utilizing the adhesive or phagocytic properties of the cells. However, most methods utilize differences in specific gravity or size of the cells. Thus, either isopycnic centrifugation or velocity sedimentation can be used. Differences in electrophoretic mobility of blood cells have also been employed for their separation. Mostly, blood cells are first separated by isopycnic centrifugation into a light fraction containing mononuclear leukocytes (monocytes + lymphocytes), basophils and a few early precursor cells, and a heavy fraction containing erythrocytes and granulocytes. Separation of monocytes from lymphocytes and basophils and of neutrophils and eosinophils from each other can also be performed by isopycnic centrifugation, owing to the differences in specific gravity among the various types of blood cell. As neutrophils and eosinophils (together called “granulocytes”) have a higher specific gravity than other leukocytes, the common method of neutrophil purification is separation over a medium of 1.077 g/cm³ and removal of the centrifugation has also been reported.