Half-life of the maternal IgG1 allotype in infants.
The residence time of maternal IgG1 in the circulation of infants was measured by monitoring f-allotypic IgG1 or f-positive tetanus toxoid antibody in genetically G1mf-negative infants. G1ma-positive maternal tetanus toxoid antibody was similarly monitored in genetically a-negative infants. Blood samples were taken from infants at the age of 1-3 days, ca. 4 months, and ca. 6 months. An exponential decay at the same rate took place from age 1-3 days to 4 months and for the 2 subsequent months. The average concentration of the maternal IgG1 had dropped to ca. 10% of the 1- to 3-day value in 4 months and to ca. 3% in 6 months. The drop was due mainly to clearance but partly also to the weight increase of the child (doubling in 6 months). By correcting for the weight increase, we calculated that ca. 17 and 7% of the original maternal IgG1 was still present at ages 4 and 6 months, respectively. The average half-life of the maternal IgG1 was thus 48.4 days. The concentration of endogenous IgG1 in the cord blood was determined by studying a separate series of mother-newborn pairs. Assuming that cross-reactions of antiallotype reagents had no effect, the highest measured concentration of f-positive IgG1 in infants of f-negative mothers was 10 mg/L, half a percent of adult heterozygote values. Crossreaction may have played a role, however, and the value must be considered the upper limit of the true concentration.
Sarvas
H
H
Department of Bacteriology and Immunology, University of Helsinki, Finland.
Seppälä
I
I
Kurikka
S
S
Siegberg
R
R
Mäkelä
O
O
D005260:Female; D005312:Fetal Blood / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D007126:Immunoglobulin Allotypes / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology*; D007129:Immunoglobulin Gm Allotypes / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008431:Maternal-Fetal Exchange / Q000276:immunology*; D011247:Pregnancy; D013745:Tetanus Toxoid / Q000276:immunology
D007126:Immunoglobulin Allotypes; D007074:Immunoglobulin G; D007129:Immunoglobulin Gm Allotypes; D013745:Tetanus Toxoid