IL11 (Interleukin-11) is a multifunctional cytokine first isolated from bone marrow-derived stromal cells. It stimulates the proliferation of hematopoietic stem cells and megakaryocyte progenitor cells and induces megakaryocyte maturation resulting in increased platelet production. Besides, IL11 is reported to induce the proliferation of human T-cells, thus, a proliferation assay was conducted to detect the bioactivity of human recombinant IL11 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 IL11. 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℃. Cell proliferation of Jurkat cells after incubation with IL11 for 72h observed by inverted microscope was shown in Figure 1. The CCK-8 data was shown in Figure 2. It was obvious that IL11 significantly promoted cell proliferation of Jurkat cells.