HUMAN NATURAL-KILLER-CELLS - A CONVENIENT PURIFICATION PROCEDURE AND THE INFLUENCE OF CRYOPRESERVATION ON CYTOTOXIC ACTIVITY

The recognition of natural killer cells as a lymphoid subpopulation wi th a distinct set of surface markers has led to the development of a v ariety of antibody-based purification methods. In this paper we descri be a rapid, three-step negative selection protocol for the purificatio n of human natural killer (NK) cells from the mononuclear cell fractio n, which is obtained by the centrifugation of peripheral blood on Fico ll-Paque. Subsequently, monocytes and B lymphocytes are removed by adh erence to nylon wool and T lymphocytes by panning with anti-CD3. With this procedure, CD3-, CD16/56+ NK cells are purified about five-fold, from 12 +/- 3% in the starting population to a final purity of 61 +/- 11 %. A further increase to greater-than-or-equal-to 70% is obtained, if an extra Ficoll centrifugation step is included. The recovery of NK cells (50%) is significantly higher than is usually achieved by previ ously described procedures. Furthermore, we show that activation of cy totoxicity, with concomitant changes in target specificity, occurs whe n frozen/thawed NK effector cells are kept in culture in order to rega in their pre-freezing cytotoxicity levels.