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. CD80 can combine with CD86, thus, a binding ELISA assay was conducted to detect the association of recombinant human CD80 with recombinant human CD86. Briefly, biotin-linked recombinant human CD80 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to CD86-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 50 μl stop solution to the wells and read at 450 nm immediately. The binding activity of recombinant human CD80 and recombinant human CD86 was shown in Figure 1, the EC50?for this effect is 0.412 ug/mL.