Prenatal stress and immune recognition of self and nonself in the primate neonate

The capacity of the neonate to respond to nonself antigens was evaluated in infant monkeys born after normal and disturbed pregnancies. Mixed lymphocy te cultures were used to test the infants' proliferative responses to mitom ycin-treated stimulator cells, either from a genetically unrelated animal o r from a virally transformed monkey cell line. Periods of daily stress for 6 weeks in mid-late pregnancy (months 3.0-4.5) resulted in a significant de crease in proliferative responses, whereas the same stressor early in pregn ancy (months 1.5-3.0) increased responses by the neonate's cells. Similar t o the late stress effect, an inhibition of proliferative responses by neona tal cells was induced by dexamethasone administered for 2 days late in preg nancy at 4.5 months after conception, 1 month before term. These findings d emonstrate that certain immune responses at birth are extremely sensitive t o prior prenatal events. Further, the bidirectional changes indicate that t here may be critical periods in gestation when the sa me extrinsic events h ave radically different effects on the fetus.