DIFFERENTIAL EFFECT OF CRYOPRESERVATION ON NATURAL-KILLER-CELL AND LYMPHOKINE-ACTIVATED KILLER-CELL ACTIVITIES

The use of lymphokine-activated killer (LAK) cell therapy in delayed t reatment requires the use of cryopreserved effector cells. The purpose of this study was to determine the optimal cryopreservation protocol for the maintaince of cytotoxic activity in mononuclear cells (MNCs). MNCs were cryopreserved with dimethyl sulfoxide or 1,2-propanediol bef ore and after 3 days of culture with recombinant interleukin 2. The ef fects of cryopreservation on cell recovery, LAK cell and natural kille r (NK) cell cytotoxic activities, and surface antigen markers were stu died. Recovery of nonactivated MNCs was higher with 1,2-propanediol th an with dimethyl sulfoxide (p<0.05). Cytotoxic activities, measured wi th a Cr-51 release assay, significantly decreased after thawing, on bo th activated cells (76.3%; range, 35.8-92.2%) and fresh cells (54.6%; range, 17.5-75.4%). A 6-day kinetic test was used to compare the cytot oxic activity of cryopreserved and fresh cells. The results showed dif ferent patterns for NK cells (cryopreserved cells had lower levels of activity than fresh cells) and LAK cells (cryopreserved cells had high er levels of activity than fresh cells). Phenotype changes of effector cells in culture, with and without cryopreservation, were monitored b y flow cytometry using monoclonal antibodies. These results were compa red with changes in the cytotoxicity of cells with and without cryopre servation. After thawing, there was a decrease in MNCs expressing CD14 and CD56. Recovery of the CD56 marker correlates with increased cytot oxic activity. Despite some loss of NK cell activity, it is concluded that MNCs may be successfully cryopreserved before their use in immuno therapeutic treatment.