Mucin 5 subtype B, also known as MUC5B, is a high molecular weight glycoprotein that belongs to the mucin family. It is primarily found in the mucus lining of the respiratory tract, where it plays a crucial role in protecting the epithelial cells from pathogens and environmental damage. It is also expressed in other tissues such as the gastrointestinal tract and the female reproductive system. The protein is secreted by goblet cells and submucosal glands and forms a viscoelastic gel that contributes to the lubrication and barrier function of mucus.Besides,Mucin 13, Cell Surface Associated (MUC13) has been identified as an interactor of MUC5B, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant mouse MUC5B and recombinant human MUC13. Briefly, biotin-linked MUC5B were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to MUC13-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 MUC5B and MUC13 was shown in Figure 1, the EC50 for this effect is 3.58ug/mL.