The half-life of IL-15 mRNA in cord (CB) (A) versus adult (APB) (B) MNCs. Actinomycin D (10 μg/mL) was added for the indicated times to cells from cord (A) and adult (B), stimulated with LPS (10 μg/mL) for 12 hours. Poly (A)⁺ RNA was analyzed by Northern blotting for the presence of IL-15 transcript (1.5 kb). The data were plotted against the time after the addition of actinomycin D. Results shown are representative of three different experiments (t_1/2 : 101 ± 5.8 minutes v 210 ± 8.2 minutes, CB v APB, P < .05, n = 3).