ヒト血清中のマンナン結合タンパク質のラジオイムノアッセイによる定量法の確立とその臨床化学的意義の検索

Abstract

In an attempt to know the physiological roles of the serum mannan-binding protein (MBP), a lectin specific for mannose and N-acetylglucosamine, a radioimmunoassay system for the human serum MBP was developed. Human serum (30 μl) was incubated with rabbit anti-human serum MBP-IgG in the presence of human serum MBP labeled with 125I-Bolton-Hunter reagent, and the separation of bound and free antigen was carried out by the 2nd antibody method. By this procedure, ～10 ng of the MBP in human sera could be assayed. The MBP in control sera dispersed in the range of 0～4.14 μg/ml serum at the 95% confidence level and the mean value was 1.82 μg/ml serum. The MBP level decreased slightly with ages. More than a half of cancer patients showed the levels lower than 1.0 μg/ml serum. The levels of patients with lysosomal storage diseases dispersed as widely as those of the controls. Total mannan-binding activity of the controls which includes the activity of MBP and that of carbohydrate-binding IgG was in the range of 238～4107 ng mannan bound/ml serum and the mean value was 988 ng mannan bound/ml serum. The ratio of the mannan-binding activity of IgG to that of the MBP varied markedly (0.1～0.9). Some cancer patients' sera showed markedly high mannan-binding activity which was ascribed to the carbohydrate-binding IgG.