IL7 (Interleukin 7) is a hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus. The interaction between IL17 and the IL7 receptor triggers a cascade of signals important for T-cell development within the thymus and survival within the periphery. It is reported that IL-7 acts on both resting and activated T cells, including Jurkat cells. Thus, a proliferation assay of recombinant human IL7 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 IL7. 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 IL7 for 72h observed by inverted microscope was shown in Figure 1. The CCK-8 data was shown in Figure 2. It was obvious that IL7 significantly promoted cell proliferation of Jurkat cells.