B-Lymphocyte Activation Antigen B7-1 (CD80) is a membrane receptor that is activated by the binding of CD28 or CTLA-4. The activated protein induces T-cell proliferation and cytokine production. This protein can act as a receptor for adenovirus subgroup B and may play a role in lupus neuropathy. A functional binding ELISA assay was conducted to detect the interaction of recombinant rat CD80 with recombinant human IL10. Briefly, recombinant rat CD80 were diluted serially in PBS, with 0.01% BSA (pH7.4). Duplicate samples of 100 ul were then transferred to IL10-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CD80 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, 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 nm immediately. The binding activity of recombinant rat CD80 and recombinant human IL10 was shown in Figure 1, the EC50?for this effect is 0.09 ug/mL.