Janus Kinase 1, also known as JAK1, is a member of the Janus kinase family, which plays a crucial role in various cellular processes, including signal transduction, immune response, and hematopoiesis. It is reported that the binding of JAK1 to IFNa2 plays an important role in immune response and antiviral defense. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human JAK1 and recombinant mouse IFNa2. Briefly, JAK1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IFNa2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-JAK1 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 human JAK1 and recombinant mouse IFNa2 was shown in Figure 1, the EC50?for this effect is 0.1 ug/mL.