THE PROLIFERATION AND FUNCTION OF HUMAN MONONUCLEAR LEUKOCYTES AND NATURAL-KILLER CELLS IN SERUM-FREE MEDIUM

A serum-free (SF) culture medium that supports the growth of several established lymphoid cell lines was developed. In an effort to develop a standardized medium for assay of human natural killer (NK) cell activity, the cytotoxic activity of peripheral blood mononuclear leukocytes (PBL) and purified large granular lymphocytes (LGL) cultured in SF medium containing interleukin 2 (IL-2) or medium containing 10% fetal bovine serum (FBS) plus IL-2 were compared. PBL had a 30% increase in cumulative net cell growth and had as high or higher cytotoxic activity after growth in SF medium than in medium containing FBS. Purified LGL had a 50% increase in cumulative net cell growth and persisted approximatley 2 wk longer in culture in medium containing FBS than in SF medium. The cytotoxic activity of cells grown in SF medium persisted during the initial 3 wk of culture. Purified LGL that were maintained and were subcultured at cell densities of 106 cells or greater per ml of either SF or FBS-containing medium had equivalent levels of cytotoxicity over a 44-day period in either medium compared with cells subcultured at a density of 5 .times. 105 cells per ml of medium. NK cells produced a cytotoxic factor (NKCF) in SF medium, and its cytotoxic activity was blocked by 10% FBS. The SF medium supplemented with IL-2 can be used as an alternative to FBS-containing medium with IL-2 for the growth of NK cells and is advantageous for the production of NKCF.