Neopterin, a marker of cell-mediated immune activation in human pregnancy.

High neopterin excretion is closely associated with activation of cell-mediated immunity. We studied urine and serum neopterin concentrations and serum interferon-gamma concentrations in normal pregnant women. In our study population, neopterin concentrations exceeded the normal range in 663 of 840 samples (79%). Neopterin levels increased with the time of pregnancy. Serum samples drawn from women in the third trimester of pregnancy also showed high neopterin concentrations in almost all cases; however, no circulating interferon-gamma was detected. Whereas neopterin is able to penetrate into the blood stream because of its small size (M = 253 D), diffusion of interferon-gamma is limited. Raised neopterin levels provide evidence for activated cell-mediated immunity during pregnancy.