| Abstract: | Summary. Samples of Immune Serum Globulin (Human) [ISG] stored for 0–11 years at 5°C were examined by ultracentrifugation, starch gel electrophoresis, and solubility in trichloroacetic acid. The extent of proteolytic degradation was dependent on the manufacturing process (salt or ethanol precipitation) and the source (venous, placental, or mixed). Incubation of ISG with added plasmin at temperatures from -23°C to 50°C showed that maximum degradation to 3.5 S material occurred at 24°C, relatively little occurred at 45°C, and none occurred at -23°C or 50°C. Placental ISG was stored, without added plasmin, for up to 2 years, and the following observations were made: considerably more proteolysis took place at 24°C than at 5°C; heating at 45°C or 50°C prior to storage at 24°C markedly reduced the extent of degradation; and the magnitude of this reduction was the same for samples heated at 45°C for 36 h, 48 h, or 72 h, or at 50°C for 72 h. Heating at 45°C produced minimal changes in the electrophoretic or anticomplementary characteristics of ISG but did result in a marked decrease in the amount of 10 S material present. |
