Associations between maternal and fetal serum levels of immune activation markers and fetal growth.

During pregnancy, signs of maternal immunologic sensitization to fetal HLA and other fetoplacental alloantigens are often detectable in peripheral blood. Presumbly, this in part reflects immune activity at the maternal-fetal interface. This response may involve activation of maternal T cells, which stimulate placental growth via lymphokine production. To shed light on this mechanism, data on placental weight, neonatal anthropometry, gestational age, fetomaternal HLA relationships (reflecting a potential for HLA allosensitization), and serum levels of three immune activation markers in maternal and cord blood were collected in a sample of 61 primiparous women and their neonates. The activation markers were soluble CD8 antigen (sCD8), interleukin-2 receptor (sIL-2R), and beta-2 microglobulin (β m). Mean fetal and maternal sCD8 and β m levels, and mean fetal sIL-2R levels were significantly higher than published norms. Fetal means for all three markers exceeded maternal means, and both sIL-2R and β m were highly correlated between mother and fetus. This suggests that fetal sIL-2R and β m levels result in part from transport or diffusion from the maternal compartment. No associations were found between fetomaternal HLA relationships, activation markers, and placental weight. The difference between the fetal and maternal β m value was significantly correlated with birth weight, controlling for chest circumference and crown-heel length. Associations between birth weight and fetomaternal HLA relationships could not be interpreted with certainty. These findings suggest that maternal immune activation and diffusion or transport of β m into fetal compartment enhances fetal growth in fat-free body mass. © 1995 Wiley-Liss, Inc.