HC favors the expansion of CD56⁺CD3^– cells. Purified CD56⁺ cells were cultured with IL-15 in the absence or presence of HC, at concentrations ranging from 10^–8 M to 10^–4 M, for 20 days and the percentages of CD3^– (▪) and CD3⁺ (□) cells were monitored at 5-day intervals. The results from one representative donor of 6 tested are presented. The percentage of CD3^– cells within the CD56⁺ population of this donor on day 0 was 64%.