Apolipoprotein C1 (APOC1), also known as Apo-CI; ApoC-I; apo-CIB; apoC-IB, is the smallest size apolipoprotein of all apolipoprotein C family (Mr = 6.6 kDa) and located at position 19q13.32. APOC1 is primarily expressed in the liver and activated when monocytes differentiate into macrophages. It plays important roles in the innate immune response as effector of glucocorticoid-mediated responses and regulator of the inflammatory process. It has anti-inflammatory activity and also can promote the differentiation of T-cells into Th1 cells and negatively regulates differentiation into Th2 cells. Besides, Apolipoprotein C3 (APOC3) has been identified as an interactor of APOC1, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human APOC1 and recombinant mouse APOC3. Briefly, APOC1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to APOC3-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-APOC1 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 APOC1 and recombinant mouse APOC3 was shown in Figure 1, the EC50 for this effect is 2.19 ug/mL.