Prolonged cryopreservation of human granulocytes.

Normal human granulocytes prepared by dextran sedimentation were cryopreserved in 10 percent dimethyl sulfoxide and 25 percent autologous plasma using controlled-rate freezing at -1 degrees C per minute. Twenty-four samples were stored from 0 to 8 months in the vapor or liquid phase of liquid nitrogen. The mean cell recovery was 58 +/- 4 percent and the mean bactericidal activity using Staphylococcus aureus was 72 +/- 4 percent. Cells stored for approximately 5 months examined with transmission electron microscopy had intact cell membranes and granules although some nuclear changes were observed. No decline in cell recovery or bactericidal activity was observed with prolonged storage and there was no advantage of liquid over vapor phase. Samples stored for over 8 months showed a 73 percent cell recovery and a 77 percent bactericidal activity. Maintenance of granulocyte function after prolonged cryopreservation in these studies suggests the feasibility of cryopreserved granulocyte transfusion therapy.