Leukemia Inhibitory Factor (LIF) is a multifunctional cytokine belonging to the interleukin-6 (IL-6) family. First identified in 1987 for its ability to inhibit the proliferation of myeloid leukemia cells and induce their differentiation, LIF is now recognized for broader biological roles. It is produced by various cell types, including fibroblasts, endothelial cells, and immune cells like T lymphocytes and macrophages. Beyond hematology, LIF plays critical roles in embryonic development—supporting the self-renewal of embryonic stem cells in mice—and tissue repair, inflammation regulation, and neural function. Its signaling occurs via binding to a heterodimeric receptor complex, activating downstream pathways like JAK-STAT and MAPK. Dysregulated LIF expression has been linked to diseases such as cancer, autoimmune disorders, and neurodegenerative conditions, making it a potential therapeutic target.Besides,IL5RA has been identified as an interactor of LIF, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human LIF and recombinant human IL5RA.Briefly, biotin-linked LIF were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100µl were then transferred to IL5RA-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50µl stop solution to the wells and read at 450nm immediately. The binding activity of LIF and IL5RA was shown in Figure 1, the EC50 for this effect is 0.37163µg/mL.