Neopterin concentrations in fetal and maternal blood: a marker of cell-mediated immune activation

Neopterin is generated by macrophages and monocytes in response to cytokine and endotoxin stimulation and is a sensitive marker of the severity of infectious-, autoimmune-, and alloimmune-mediated inflammatory disorders. This study was designed to evaluate fetal and maternal neopterin concentrations during the second half of pregnancy.

We conducted a cross-sectional analysis of serum neopterin values with a sensitive radioimmunoassay in 35 paired fetal and maternal and 8 neonatal samples. The fetal and maternal samples were obtained between 20 and 38 weeks' gestation at the time of diagnostic cordocentesis. All maternal, fetal, and neonatal samples were derived from uncomplicated pregnancies resulting in term delivery of appropriately grown fetuses.

Fetal neopterin concentrations increased across gestation (r = 0.64, P <.001), and mean values were significantly higher than paired maternal values (6.28 [+/-2.44] ng/mL vs 2.05 [+/-0.87] ng/mL, P <.001]. In contrast, maternal neopterin concentrations did not correlate with gestational age (r = 0.22, P =.24). No significant correlation was found between fetal and maternal values (r = 0.34, P =.07).

Fetal neopterin values rise significantly across gestation. They are substantially greater than maternal levels and are not correlated significantly with paired maternal levels. These findings are the first report of a physiologically normal range for fetal neopterin concentrations in a sample of uncomplicated pregnancies. The values suggest progressive increases in fetal cell-mediated immunity and macrophage-monocyte activation as gestation progresses.