Ontogeny of human T and B lymphocytes during stressed and normal gestation: phenotypic analysis of umbilical cord lymphocytes from term and preterm infants.

Cord blood lymphocytes from premature and stressed term infants were phenotyped and contrasted with T and B lymphocytes from healthy newborns at term. Cytofluorometric analysis shows that in the early third trimester, 80-85% of fetal T cells belong to the T4+ inducer population, and 10% to the T8+ suppressor/cytotoxic subset. As gestation progresses, the T4:T8 ratio shifts toward adult values and there is an increase in expression of the mature antigen, T12. The B-cell-differentiation antigens B1, B2, and B4 do not appear to change during gestation in healthy infants. Antenatal stress which threatens fetal survival, however, leads to circulating cells of both lineages which are phenotypically less mature than expected for gestational age. Most notably, in response to severe antenatal hypoxic stress, cells expressing the very early B-cell markers B2 and B4 increase and exceed the numbers of more mature B1+ cells in cord blood.