Interleukin-5 (IL-5), a secreted glycoprotein, is a member of ?the hematopoietic family. Interleukin 5 has been shown to??stimulate?the proliferation of TF-1 cells. To test this effect, TF-1 cells were seeded into triplicate wells of 96-well plates at a density of 2 x 104 cells/well and incubated for 72h in the presence or absence of various concentrations of recombinant mouse IL-5 at 37 ℃.?The growth of cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8(CCK-8). Briefly, 10 μl of CCK-8 solution was added to each well of the plate，then measure the absorbance at 450 nm using a microplate reader after incubating the plate for 1-4 hours at 37 ℃ . Cell proliferation of TF-1 cells after incubation with IL-5 for 72h observed by inverted microscope was shown in Figure 1. The dose-effect curve of recombinant mouse IL-5 was shown in Figure 2. It was obvious that it significantly promoted cell proliferation of TF-1 cells. The ED50 for this effect is typically 2.9 ng/ml.