Oral exposure to maternal antigens is important in maintaining tolerance and preventing NIMA-induced sensitization. (A) Left panel shows average levels of MMc found in the heart, liver, and lungs in newborn offspring (less than 1 day old). Levels of MMc in heart, liver, and lungs of the newborn offspring are depicted in the right panel. (B) Newborn NIMA^d-exposed mice were either nursed by the birth mother, or separated from their BDF₁ mothers within 6 hours of birth and foster-nursed (F.N.) by B6 females. A control group of 3 NIMA^d-exposed newborns were separated from their mothers and foster-nursed by another BDF₁ female. Levels of H2D^d Mc (average of the organs tested) of the adult NIMA^d-exposed mice (6-8 weeks old) nursed by their own mothers (NIMA^d), or foster-nursed by B6 (F.N. by B6) or BDF₁ mice (F.N. by BDF₁) are shown. (C) Comparison of DTH responses to BDF₁ antigens between NIMA^d and NIMA^d foster-nursed by B6. For a positive control response to BDF₁ alloantigen, some NIPA^d control mice were injected intravenously with BDF₁ splenocytes 2 weeks before DTH assay and used as a source of sensitized splenocytes. The horizontal lines represent mean values of the observations.