Pro-IL16 (Interleukin16) is a 631 amino acid precursor molecule, which is then cleaved into different isoforms. Researches have shown that the recombinant human IL16, containing C-terminal 130 amino acids, has same bioactivity as the natural secreted human IL16. Besides, IL16 has been considered to stimulate the proliferation of Jurkat cells at low dose (10-9 M). Thus, a proliferation assay of recombinant human IL16 was conducted using Jurkat cells. Briefly, Jurkat cells were seeded into triplicate wells of 96-well plates at a density of 10, 000 cells/well in RPMI-1640 with the addition of various concentrations of IL16. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10μL of CCK-8 solution was added to each well of the plate, then the absorbance at 450nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37°C. Cell proliferation of Jurkat cells after incubation with IL16 for 72h observed by inverted microscope was shown in Figure 1. The CCK-8 data was shown in Figure 2. It was obvious that IL16 significantly promoted cell proliferation of Jurkat cells.