α-Fetoprotein and Human Lymphocyte Subpopulations

Peripheral blood lymphocytes were incubated with varying concentrations of α-fetoprotein and enumerated for total and “active” T lymphocytes, B lymphocytes, and their proliferative responses to phytohemagglutinin. No significant effect was observed on total T or B lymphocyte proportions. However, there was a dose-related increase in proportions of the so called “active” T lymphocytes. the response of human lymphocytes to phytohemagglutinin was markedly depressed. The alteration in the proportion of active T cells and the inhibition of T lymphocyte response to phytohemagglutinin by α-fetoprotein occurred at higher concentrations than are present in amniotic fluid, serum of pregnant women, or serum of adults, but well within the range reached in fetal serum. The immunoregulatory role of α-fetoprotein is discussed.