Membrane-bound IL-21 promotes sustained ex vivo proliferation of human natural killer cells. oleh Cecele J Denman, Vladimir V Senyukov, Srinivas S Somanchi, Prasad V Phatarpekar, Lisa M Kopp, Jennifer L Johnson, Harjeet Singh, Lenka Hurton, Sourindra N Maiti, M Helen Huls, Richard E Champlin, Laurence J N Cooper, Dean A Lee