POSITIVE SELECTION OF NK1.1(+) CELLS ON A MAGNETIC CELL SEPARATOR (MACS)

Natural killer (NK) cells are involved not only in resistance to tumor s and infection, but also in some transplantation reactions. A specifi c, inexpensive method for purifying large numbers of NK cells is often required. All NK cells in H-2(b) mice express the surface marker NK1. 1. We report a method for positively selecting NK1.1(+) spleen cells f rom normal and Poly I:C-stimulated C56Bl/6 mice using a magnetic cell separation technique known as MACS. Our results show that cytotoxic ac tivity directed at YAC-1 target cells by normal and Poly I:C-stimulate d spleen cells could be increased five-fold using this method. We also found that spleen cells from mice given Poly I:C could lyse NK-resist ant, BW1100 target cells, and that this activity could be increased tw o-fold. Flow cytometry analysis of Poly I:C-stimulated, MACS enriched, NK1.1(+) spleen cells revealed the presence of two subpopulations: on e consisting of LGL and the other consisting of smaller, agranular lym phocytes (SAL). After enrichment, the percentage of NK1.1(+) spleen ce lls increased from 69% to 91% in the LGL subpopulation and from 33% to 73% in the SAL subpopulation. These results clearly demonstrate the e ffectiveness of the MACS technique for purifying large numbers of NK1. 1(+) cells for both flow cytometric and functional analyses.