RIGI and viral infectious disease: Thirdly, in the presence of poly(I:C) at 2 μg/ml, high doses of human LGP2 elicit a most significant inhibition of RIG-I signaling with a wide dose window of RIG-I; and in the presence of poly(I:C) at 4 ng/ml, human LGP2 downregulates RIG-I signaling with a very narrow dose window of RIG-I, particularly when LGP2 is expressed at a low dose (5 ng), strongly indicating that human LGP2 inhibits RIG-I signaling mainly at the late stage of virus infection.