Lymphocyte response to phytohaemagglutinin in the presence of serum from pregnant women: correlation with serum levels of alpha-foetoprotein.

The effect of sera from women in different stages of pregnancy on cultures of human lymphocytes stimulated with phytohaemagglutinin (PHA) has been studied and correlated with alpha-foetoprotein (AFP) levels. Sera taken before the twentieth week of gestation showed low levels of AFP and failed to inhibit lymphocyte proliferation. Inhibition was obtained with 38.5% of sera taken from weeks 20 to 30 and with 51.7% of sera after the thirtieth week of pregnancy. Average serum levels of AFP also increased with advanced gestation, but a consistent correlation was not found between AFP concentration and inhibitory activity for every individual serum tested. Lymphocytes from pregnant women or from normal blood donors behaved in the same way in these tests. The mechanisms of inhibition and the role of AFP are discussed.