Native α?-acid glycoprotein from human plasma. Glycoprotein used for the study of the structure of oligosaccharide units. Consists of 40 - 45% carbohydrate. Present in human plasma at concentrations of 55 - 140 mg/100 ml. Clinically,α?-AG is an acute-phase reactant that, together with haptoglobin, indicates acute inflammation. Selectively suppresses the augmentation of NK cell activity by IFN-α and IFN-γ. Theα?-AG:α?-antitrypsin ratio is useful in diagnosis of liver disease. A sialic acid-deficientα?-AG has been observed in serum or urine of patients with Hodgkin’s disease, psoriatic arthritis, diabetes, and chronic myeloid leukemia. Sialic acid-deficientα?-AG has an affinity for vitamin B??.