Immunoglobulin IgG1 Metabolism in New Born Calves

Abstract

The half-life of IgG1 immunoglobulin was measured in 6 neonatal calves following a meal of 125I labeled IgG1 in colostrum derived from their dams. The half-life as measured by the decrease in plasma concentration of IgG1 was 19.9 .+-. 1.9 days. The half-life as measured by the disappearance of 125I IgG1 from the plasma was 11.5 .+-. .6 days. The latter value is closer to the true half-life because it is not affected by endogenous production of IgG1 by the tissues of the young calf. A decrease in the specific activity of plasma 125I IgG1 with time representing the body pool of IgG1 (half-life 25.8 .+-. 6.1 days) suggests that the calf from birth to about 20 days of age is capable of synthesizing a significant amount of IgG1 immunoglobulin.