Transplacental passage of insulin complexed to antibody.

Abstract

The passage of plasma proteins across the placental barrier in humans is highly selective. Free maternal insulin does not cross the normal maternofetal barrier, although insulin-binding antibodies are detected in newborn infants whose diabetic mothers received insulin therapy. A human antiserum (that permits distinction between human and bovine insulins) was used to show that insulin in the cord blood of each of 2 neonates of insulin-treated diabetic mothers was, in part, animal insulin. The higher the antibody titer of the mother, the greater was the total insulin in the cord plasma and the greater the fraction that was animal insulin. In case 1 cord plasma insulin was 0.7 U/l, of which 10% was animal insulin; in case 2 cord plasma insulin was 3.5 U/l, of which 25% was animal insulin. The demonstration that antigen restricted from transplacental passage can be transferred while complexed to antibody suggests that such fetal exposure may induce partial or total immunologic unresponsiveness subsequently if the fetus is rechallenged with the same antigen.