IFNgamma R2 (Interferon gamma receptor 2; also called IFN gamma R beta IFN gamma ?RII, or AF1) is a 6064?kDa type?I transmembrane glycoprotein that is a member of the class?II cytokine receptor family of molecule). It is highly expressed on the surfaces of myeloid cells, moderately expressed on B cells, and poorly expressed on the surfaces of T cells. IFNγR2 is a cell-surface receptor that is required for interferon-γ signalling and therefore plays a critical immunoregulatory role in innate and adaptive immunity against viral and also bacterial and protozoal infections. IFNgR2 have been confirmed to mediate down-stream JAK-STAT signaling pathway in mammals.?It is widely expressed as part of a preassembled cell surface multimeric complex. In the absence of IFNgamma, the complex contains two each of IFNgamma R1, R2 and Jak1 molecules. Binding of IFNgamma to IFNgamma R1 recruits Jak2 to IFN-gamma R2 and initiates phosphorylation, STAT1 binding, conformational changes and transcriptional regulation, which mainly inhibits proliferation and/or promotes apoptosis. A functional binding ELISA assay was conducted to detect the interaction of recombinant human IFNgR2 and recombinant rat JAK2. Briefly, biotin-linked IFNgR2 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to JAK2-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 IFNgR2 and JAK2 was shown in Figure 1, the EC50?for this effect is 1.02 ug/mL.