The cryopreservation of leukaemia cells: morphological and functional changes

Stored autologous haemopoietic cells may be used to repopulate the bone marrow of patients in the advanced stages of different leukaemias who have received cytotoxic drugs. We have used a continuous flow blood cell separator to collect peripheral blood leucocytes from patients with chronic granulocytic leukaemia (CGL) before treatment. We also collected bone marrow cells from patients with CGL and from patients with acute myeloid leukaemia in complete remission. The collected cells were frozen at I degree C per minute using dimethyl sulphoxide as cryoprotective agent and stored in liquid nitrogen. For reconstitution of frozen cells we found that the use of dextran II0 inhibited leucoagglutination. The viability and function of the reconstituted leucocytes were assessed by their morphological appearance, their capacity to phagocytose and kill Candida albicans organisms, their ability to reduce the dye nitroblue tetrazolium (NBT) in vitro and to incorporate tritiated thymidine into DNA and by the growth of colony forming units (CFUc) in agar culture. With this method of cryopreservation the phagocytic function of mature neutrophils is retained to some extent but their capacity to reduce NBT and their microbicidal activity are completely lost. In contrast CFUc may remain after storage for periods of at least 2 years.