Effect of transplacental transfer of antibody to intrinsic factor.

The absence of detectable intrinsic factor (I.F.) was observed in the gastric juice of a newborn with transplacentally transferred blocking antibody to I.F. (titer of 1:16). I.F. was first detected in the infant's gastric juice at 1 month of age when the circulating I.F. antibody had decreased to a titer of 1:4. Evidence is presented to suggest that, at least in newborns, circulating antibody to I.F. may suppress the gastric I.F. The possible mechanisms responsible for this suppression are discussed.