Nuclear Factor kappa B2 (NFkB2), also known as p100, is a subunit of the NF-kappa B (NFkB) family of transcription factors. NFkB2 plays an important role in immune response and inflammation. It is involved in regulating the expression of a variety of genes, including those encoding cytokines, chemokines, adhesion molecules, and acute phase response proteins. RELB-NFkB2 heterodimer regulates the expression of genes associated with immune response and inflammation in cells. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant mouse NFkB2 and recombinant human RELB. Briefly, NFkB2 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to RELB-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-NFkB2 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630 nm immediately. The binding activity of recombinant mouse NFkB2 and recombinant human RELB was shown in Figure 1, the EC50 for this effect is 0.23 ug/mL.