Tumor necrosis factor ligand superfamily member 13B protein (TNFSF13B) also known as B-cell activating factor (BAFF) is a cytokine that belongs to the tumor necrosis factor (TNF) ligand family. This cytokine is a ligand for receptors TNFRSF13B/TACI, TNFRSF17/BCMA, and TNFRSF13C/BAFF-R. This cytokine is expressed in B cell lineage cells, and acts as a potent B cell activator. It has been also shown to play an important role in the proliferation and differentiation of B cells. Besides, Integrin Beta 1 (ITGb1) has been identified as an interactor of TNFSF13B, thus a binding ELISA assay was conducted to detect the interaction of recombinant human TNFSF13B and recombinant human ITGb1. Briefly, TNFSF13B were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100ul were then transferred to ITGb1-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-TNFSF13B pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 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 TNFSF13B and ITGb1 was shown in Figure 1, the EC50 was 0.74~0.93 ug/ml.