Population dynamics of human activated natural killer cells in culture

The growth kinetics and population dynamics of recombinent interleukin‐2 (rlL‐2) stimulated human natural killer (NK) cell–enriched populations were studied in vitro. The NK‐enriched populations was obtained from normal peripheral blood mononuclear cells (PBMNC) by immunomagnetic bead depletion of CD3⁺ and CD5⁺ T cells. The growth kinetics of NK cells, T cells, monocytes, and total cells are shown. In the absence of PBMNC accessory cells, the NK‐enriched population showed limited expansion. In the presence of PBMNC accessory cells, the NK‐enriched population expanded threefold more than in the absence of accessory cells due to increased NK cell growth rate and increased duration of exponential growth. Using a Transwell system, which separates two cell population by a polycarbonate membrane, the accessory cells were shown to act on the NK‐enriched population via a diffusible factor. Accessory cell conditioned media was able to replace the accessory cell population to stimulate NK cell expansion. A monocyte‐enriched population prepared by sheep red blood cell rosetting of T cells was extensively phenotyped and compared with the NK‐enriched populations. Although the final cultured cells were phenotypically homogeneous for CD56⁺/CD3⁻ NK cells, the initial NK precusor populations appear to be different. Namely, the NK cell precursors in the monocyte‐enriched population were predominantly CD56⁺/CD2⁻. Kinetic equations were formulated for this culture system and the effects of major culture variables are investigated.